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Sample records for granular bentonite material

  1. Granular MX-80 bentonite as buffer material: a focus on swelling characteristics

    International Nuclear Information System (INIS)

    Rizzi, M.; Laloui, L.; Salager, S.; Marschall, P.

    2010-01-01

    Document available in extended abstract form only. The Swiss High Level Waste (HLW) disposal concept envisages the emplacement of the waste canisters in horizontal tunnels excavated at a depth of several hundred meters in an over-consolidated clay-stone formation. After waste emplacement the disposal tunnels are backfilled with MX-80 granular bentonite. Research activities are presented in this paper, aimed at characterising the geomechanical behaviour of the MX-80 granular bentonite and at providing the theoretical framework for modelling its response to thermo-hydro- mechanical (THM) perturbations. From the experimental point of view, a series of tests has been designed in order to extract constitutive data and to assess the temperature and suction effects on the mechanical behaviour of the bentonite, paying particular attention in the investigation to the swelling behaviour of the material. As for the theoretical framework an elasto-plastic constitutive model has been developed to take into account those coupled processes of stress, capillary pressure, and temperature to which the bentonite will be submitted,. Bentonite is mainly composed of the smectite mineral montmorillonite with a high swelling capacity which may provide sufficient sealing properties to seal the tunnel without gaps and to restore the buffer continuity. In fact, as bentonite hydrates in the repositories it will expand in those areas where it is allowed and will exert a swelling pressure where the material is confined. The results of both confined and free swelling tests are presented. Confined tests are aiming at determining the pressure applied by the material during complete saturation under isochoric conditions, whereas in the free swelling tests the strain on hydration is measured. Some results from confined swelling tests at ambient temperature are presented. The specimen is compacted uniaxially directly in the cells, the initial dry density being chosen in the range between 1.6 and 1

  2. Swelling pressure and water absorption property of compacted granular bentonite during water absorption

    International Nuclear Information System (INIS)

    Oyamada, T.; Komine, H.; Murakami, S.; Sekiguchi, T.; Sekine, I.

    2012-01-01

    Document available in extended abstract form only. Bentonite is currently planned to be used as buffer materials in engineered barrier of radioactive waste disposal. Granular bentonites are expected as the materials used in constructions as buffer materials by in-situ compaction methods. After applying these buffer materials, it is expected that the condition of the buffer area changes in long-term by the seepage of groundwater into buffer area. Therefore, it is important to understand water movement and swelling behavior of the buffer materials for evaluating the performance of engineered barrier. In this study, we investigated water absorption property and swelling pressure of compacted granular bentonite. Specifically, the process of swelling pressure and amount of water absorption of granular bentonite-GX (Kunigel-GX, produced at the Tsukinuno mine in Japan) were observed by laboratory tests. To discuss the influence of maximum grain size of bentonite particle on swelling pressure and water absorption property, two types of samples were used. One is granular sample which is Bentonite-GX controlled under 2 mm the maximum grain size, the other is milled sample which is Bentonite-GX with the maximum grain size under 0.18 mm by milling with the agate mortar. In addition, the mechanism on the swelling pressure of compacted granular bentonite was considered and discussed. In the cases of granular sample, swelling pressure increases rapidly, then gradually continues to increase up to maximum value. In the cases of milled sample, swelling pressure also increases rapidly at first. However, then its value decreases before progressing of gradual increase continues. Especially, this trend was clearly observed at a relatively low dry density. At the peaks of these curves, the swelling pressure of granular samples is lower than that of milled samples. In addition, the increasing of swelling pressure by the time the peak observed during the process of swelling pressure from

  3. Buffer construction technique using granular bentonite

    International Nuclear Information System (INIS)

    Masuda, Ryoichi; Asano, Hidekazu; Toguri, Satohito; Mori, Takuo; Shimura, Tomoyuki; Matsuda, Takeshi; Uyama, Masao; Noda, Masaru

    2007-01-01

    Buffer construction using bentonite pellets as filling material is a promising technology for enhancing the ease of repository operation. In this study, a test of such technology was conducted in a full-scale simulated disposal drift, using a filling system which utilizes a screw conveyor system. The simulated drift, which contained two dummy overpacks, was configured as a half-cross-section model with a height of 2.22 m and a length of 6.0 m. The average dry density of the buffer obtained in the test was 1.29 Mg/m 3 , with an angle of repose of 35 to 40 degrees. These test results indicate that buffer construction using a screw conveyor system for pellet emplacement in a waste disposal drift is a promising technology for repositories for high level radioactive wastes. (author)

  4. Quality assurance of the bentonite material

    International Nuclear Information System (INIS)

    Ahonen, L.; Korkeakoski, P.; Tiljander, M.; Kivikoski, H.; Laaksonen, R.

    2008-05-01

    This report describes a quality assurance chain for the bentonite material acquisition for a nuclear waste disposal repository. Chemical, mineralogical and geotechnical methods, which may be applied in quality control of bentonite are shortly reviewed. As a case study, many of the presented control studies were performed for six different bentonite samples. Chemical analysis is a very reliable research method to control material homogeneity, because the accuracy and repeatability of the study method is extremely good. Accurate mineralogical study of bentonite is a complicated task. X-ray diffractometry is the best method to identify smectite minerals, but quantitative analysis of smectite content remains uncertain. To obtain a better quantitative analysis, development of techniques based on automatic image analysis of SEM images is proposed. General characteristics of bentonite can be obtained by rapid indicator tests, which can be done on the place of reception. These tests are methylene blue test giving information on the cation exchange capacity, swelling index and determination of water absorption. Different methods were used in the determination of cation exchange capacity (CEC) of bentonite. The results indicated differences both between methodologies and between replicate determinations for the same material and method. Additional work should be done to improve the reliability and reproducibility of the methodology. Bentonite contains water in different modes. Thus, different determination methods are used in bentonite studies and they give somewhat dissimilar results. Clay research use frequently the so-called consistency tests (liquid limit, plastic limit and plasticity index). This study method does, however, not seem to be very practical in quality control of bentonite. Therefore, only the determination of liquid limit with fall-cone method is recommended for quality control. (orig.)

  5. Quality control and characterization of bentonite materials

    International Nuclear Information System (INIS)

    Kiviranta, L.; Kumpulainen, S.

    2011-12-01

    Before bentonite material is taken into use in performance testing, the quality of the material needs to be checked. Three high grade bentonite materials: two natural Nabentonites from Wyoming, and one natural Ca-bentonite from Milos, were characterized. Each material was characterized using duplicate or triplicate samples in order to study variability in material quality in batches. The procedure consisted of basic acceptance testing (water ratio, CEC, swelling index, liquid limit, and granule size distribution), advanced acceptance testing (exchangeable cations, chemical and mineralogical composition, density, swelling pressure and hydraulic conductivity) and complementary testing (herein surface area, water absorption capacity, montmorillonite composition, grain size distribution and plastic limit). All three materials qualified the requirements set for buffer bentonite for CEC, smectite content, swelling pressure, and hydraulic conductivity. Wyoming bentonites contained approximately 88 wt.% of smectite, and Milos bentonite 79 wt.% of smectite and 3 wt.% of illite. Precision of smectite analyses was ±2 %, and variances in composition of parallel samples within analytical errors, at least for Wyoming bentonites. Accuracy of quantitative analyses for trace minerals such as gypsum, pyrite or carbonates, was however low. As the concentrations of these trace minerals are important for Eh or pH buffering reactions or development of bentonite pore water composition, normative concentrations are recommended to be used instead of mineralogically determined concentrations. The swelling pressures and hydraulic conductivities of different materials were compared using EMDD. Swelling pressure was relatively higher for studied Cabentonite than for the studied Na-bentonites and the difference could not be explained with different smectite contents. Hydraulic conductivities seemed to be similar for all materials. The results of index tests correlated with the smectite content

  6. Exchangeability of bentonite buffer and backfill materials

    Energy Technology Data Exchange (ETDEWEB)

    Savage, D. [Savage Earth Associates Ltd, Bournemouth (United Kingdom); Arthur, R. [Intera Inc, Ottawa, ON, (Canada); Luukkonen, A.

    2012-08-15

    Clay-based buffer and tunnel backfill materials are important barriers in the KBS-3 repository concept for final disposal of spent nuclear fuel in Finland. One issue that is relevant to material properties is the degree to which different bentonite compositions can be regarded as interchangeable. In Posiva's current repository design, the reference bentonite composition is MX-80, a sodium montmorillonite dominated clay. Posiva would like to be able to use bentonite with Ca-montmorillonite as the dominant clay mineral. However, at this stage, it is not clear what supporting data need to be acquired/defined to be able to place the state of knowledge of Ca-bentonite at the same level as that of Na-bentonite. In this report, the concept of bentonite exchangeability has been evaluated through consideration of how bentonite behaviour may be affected in six key performance-relevant properties, namely (1) mineralogical composition and availability of materials, (2) hydraulic conductivity, (3) mechanical and rheological properties, (4) long-term alteration, (5) colloidal properties, and (6) swelling pressure. The report evaluates implications for both buffer and backfill. Summary conclusions are drawn from these sections to suggest how bentonite exchangeability may be addressed in regulatory assessments of engineered barrier design for a future geological repository for spent fuel in Finland. Some important conclusions are: (a) There are some fundamental differences between Ca- and Na-bentonites such as colloidal behaviour, pore structure and long-term alteration that could affect the exchangeability of these materials as buffer or backfill materials and which should be further evaluated; (b) Additional experimental data are desirable for some issues such as long-term alteration, hydraulic properties and swelling behaviour, (c) The minor mineral content of bentonites is very variable, both between different bentonites and within the same bentonite type, it is not clear

  7. Thermal conductivity of granular materials

    Energy Technology Data Exchange (ETDEWEB)

    Buyevich, Yu A

    1974-01-01

    Stationary heat transfer in a granular material consisting of a continuous medium containing spherical granules of other substances is considered under the assumption that the spatial distribution of granules is random. The effective thermal conductivity characterizing macroscopic heat transfer in such a material is expressed as a certain function of the conductivities and volume fractions of the medium and dispersed substances. For reasons of mathematical analogy, all the results obtained for the thermal conductivity are valid while computing the effective diffusivity of some admixture in granular materials as well as for evaluation of the effective electric conductivity or the mean dielectric and magnetic permeabilities of granular conductors and dielectrics. (23 refs.)

  8. Bentonite as a waste isolation pilot plant shaft sealing material

    International Nuclear Information System (INIS)

    Daemen, J.; Ran, Chongwei

    1996-12-01

    Current designs of the shaft sealing system for the Waste Isolation Pilot Plant (WIPP) propose using bentonite as a primary sealing component. The shaft sealing designs anticipate that compacted bentonite sealing components can perform through the 10,000-year regulatory period and beyond. To evaluate the acceptability of bentonite as a sealing material for the WIPP, this report identifies references that deal with the properties and characteristics of bentonite that may affect its behavior in the WIPP environment. This report reviews published studies that discuss using bentonite as sealing material for nuclear waste disposal, environmental restoration, toxic and chemical waste disposal, landfill liners, and applications in the petroleum industry. This report identifies the physical and chemical properties, stability and seal construction technologies of bentonite seals in shafts, especially in a saline brine environment. This report focuses on permeability, swelling pressure, strength, stiffness, longevity, and densification properties of bentonites

  9. Bentonite as a waste isolation pilot plant shaft sealing material

    Energy Technology Data Exchange (ETDEWEB)

    Daemen, J.; Ran, Chongwei [Univ. of Nevada, Reno, NV (United States)

    1996-12-01

    Current designs of the shaft sealing system for the Waste Isolation Pilot Plant (WIPP) propose using bentonite as a primary sealing component. The shaft sealing designs anticipate that compacted bentonite sealing components can perform through the 10,000-year regulatory period and beyond. To evaluate the acceptability of bentonite as a sealing material for the WIPP, this report identifies references that deal with the properties and characteristics of bentonite that may affect its behavior in the WIPP environment. This report reviews published studies that discuss using bentonite as sealing material for nuclear waste disposal, environmental restoration, toxic and chemical waste disposal, landfill liners, and applications in the petroleum industry. This report identifies the physical and chemical properties, stability and seal construction technologies of bentonite seals in shafts, especially in a saline brine environment. This report focuses on permeability, swelling pressure, strength, stiffness, longevity, and densification properties of bentonites.

  10. HYPERELASTIC MODELS FOR GRANULAR MATERIALS

    Energy Technology Data Exchange (ETDEWEB)

    Humrickhouse, Paul W; Corradini, Michael L

    2009-01-29

    A continuum framework for modeling of dust mobilization and transport, and the behavior of granular systems in general, has been reviewed, developed and evaluated for reactor design applications. The large quantities of micron-sized particles expected in the international fusion reactor design, ITER, will accumulate into piles and layers on surfaces, which are large relative to the individual particle size; thus, particle-particle, rather than particle-surface, interactions will determine the behavior of the material in bulk, and a continuum approach is necessary and justified in treating the phenomena of interest; e.g., particle resuspension and transport. The various constitutive relations that characterize these solid particle interactions in dense granular flows have been discussed previously, but prior to mobilization their behavior is not even fluid. Even in the absence of adhesive forces between particles, dust or sand piles can exist in static equilibrium under gravity and other forces, e.g., fluid shear. Their behavior is understood to be elastic, though not linear. The recent “granular elasticity” theory proposes a non-linear elastic model based on “Hertz contacts” between particles; the theory identifies the Coulomb yield condition as a requirement for thermodynamic stability, and has successfully reproduced experimental results for stress distributions in sand piles. The granular elasticity theory is developed and implemented in a stand- alone model and then implemented as part of a finite element model, ABAQUS, to determine the stress distributions in dust piles subjected to shear by a fluid flow. We identify yield with the onset of mobilization, and establish, for a given dust pile and flow geometry, the threshold pressure (force) conditions on the surface due to flow required to initiate it. While the granular elasticity theory applies strictly to cohesionless granular materials, attractive forces are clearly important in the interaction of

  11. Impact Compaction of a Granular Material

    Science.gov (United States)

    Fenton, Gregg; Asay, Blaine; Todd, Steve; Grady, Dennis

    2017-06-01

    The dynamic behavior of granular materials has importance to a variety of engineering applications. Although, the mechanical behavior of granular materials have been studied extensively for several decades, the dynamic behavior of these materials remains poorly understood. High-quality experimental data are needed to improve our general understanding of granular material compaction physics. This paper describes how an instrumented plunger impact system can be used to measure the compaction process for granular materials at high and controlled strain rates and subsequently used for computational modelling. The experimental technique relies on a gas-gun driven plunger system to generate a compaction wave through a volume of granular material. This volume of material has been redundantly instrumented along the bed length to track the progression of the compaction wave, and the piston displacement is measured with Photon Doppler Velocimetry (PDV). Using the gathered experimental data along with the initial material tap density, a granular material equation of state can be determined.

  12. Bentonite as a backfill material for shallow land repositories

    International Nuclear Information System (INIS)

    Yalmali, V.S.; Deshingkar, D.S.

    2001-01-01

    Two commercially available indigenous bentonite samples were evaluated for their cesium and strontium sorption properties in distilled water and surface water. By converting them into sodium form, the distribution coefficients for both cesium (I) and strontium (II) increased. Sodium bentonite was recommended because of high sorption capacity for Cs(I), Mg(II) and Sr(II) for use as backfill material in shallow land repositories where cement waste form containing Cs, Sr and Be wastes are disposed. (author)

  13. bentonite-sand mixture as new backfill/buffer material

    International Nuclear Information System (INIS)

    Cui Suli; Liu Jisheng; Zhang Huyuan; Liang Jian

    2008-01-01

    The mixture of bentonite and quartz sand is suggested as a new backfill/buffer material for geological disposal of HLW. To improve the further design of underground laboratory and in-situ industrial construction test, the optimization of sand addition to bentonite is focused at present research stage. Based on summarizing the research results abroad, laboratory tests were conducted on the mixture of GMZ001 bentonite and quartz sand, such as compaction test and swelling tests etc. Test data shows that GMZ bentonite-sand mixture exhibits a favorite compaction with a 30% sand addition, a highest swelling pressure with a 20% sand addition, and a decreasing plasticity with increases in sand addition and pore liquid concentration. (authors)

  14. Characterization of Unbound Granular Materials for Pavements

    NARCIS (Netherlands)

    Araya, A.A.

    2011-01-01

    This research is focused on the characterization of the mechanical behavior of unbound granular road base materials (UGMs). An extensive laboratory investigation is described, in which various methods for determination of the mechanical properties of granular materials are examined for their

  15. Shear failure of granular materials

    Science.gov (United States)

    Degiuli, Eric; Balmforth, Neil; McElwaine, Jim; Schoof, Christian; Hewitt, Ian

    2012-02-01

    Connecting the macroscopic behavior of granular materials with the microstructure remains a great challenge. Recent work connects these scales with a discrete calculus [1]. In this work we generalize this formalism from monodisperse packings of disks to 2D assemblies of arbitrarily shaped grains. In particular, we derive Airy's expression for a symmetric, divergence-free stress tensor. Using these tools, we derive, from first-principles and in a mean-field approximation, the entropy of frictional force configurations in the Force Network Ensemble. As a macroscopic consequence of the Coulomb friction condition at contacts, we predict shear failure at a critical shear stress, in accordance with the Mohr-Coulomb failure condition well known in engineering. Results are compared with numerical simulations, and the dependence on the microscopic geometric configuration is discussed. [4pt] [1] E. DeGiuli & J. McElwaine, PRE 2011. doi: 10.1103/PhysRevE.84.041310

  16. Database on gas migration tests through bentonite buffer material

    International Nuclear Information System (INIS)

    Tanai, Kenji

    2009-02-01

    Carbon steel is a candidate material for an overpack for geological disposal of high-level radioactive waste in Japan. The corrosion of the carbon steel overpack in aqueous solution under anoxic conditions will cause the generation of hydrogen gas, which may affect hydrological and mechanical properties of the bentonite buffer. To evaluate such an effect of gas generation, it is necessary to develop a model of gas migration through bentonite buffer material taking account of data obtained from experiments. The gas migration experiments under both unsaturated and saturated conditions have been carried out to clarify the fundamental characteristics of bentonite for gas migration. This report compiles the experimental data obtained from gas migration tests for buffer material which has been conducted by JAEA until December, 2007. A CD-ROM is attached as an appendix. (author)

  17. Water uptake and stress development in bentonites and bentonite-sand buffer materials

    International Nuclear Information System (INIS)

    Dixon, D.A.; Wan, A.W-L.; Gray, M.N.; Miller, S.H.

    1996-10-01

    The development of swelling pressure and the transfer of pore water pressures through dense bentonite and bentonite-sand materials are examined in this report. This report focuses on the swelling pressure and total pressure developed in initially unsaturated specimens allowed access to free water on one end. The bentonite in this wetted region rapidly develops its full swelling pressure and this pressure is transferred upwards through the specimen. Hence, the bentonite plug will exert a pressure approximately equivalent to the swelling pressure even though only a small region of the plug is actually saturated. A number of specimens were tested with total pressure sensors mounted normal and parallel to the axis of compaction. Lateral pressures developed long before the wetting front reached sensor locations, suggesting stress transfer through the unsaturated portions of these specimens. On achieving saturation, specimens were found to have similar swelling pressures both normal to and parallel to the axis of compaction. This indicates that there is little or no specimen anisotropy induced by the compaction process. Tests were conducted on specimens allowed only to take on a limited quantity of water and it was found that density anisotropy was induced as the result of the swelling pressures generated by the buffer. The wetted skin of buffer developed a considerable pressure and compressed a region of buffer immediately above the wetted region. The results suggest that the buffer material placed in a disposal vault will rapidly develop and transfer swelling pressures as a result of the saturation of a limited region or 'skin' within the emplacement site. The total pressure ultimately present on the container surface should be the sum of the swelling and hydraulic components. (author). 14 refs., 4 tabs., 8 figs

  18. Activation of a Ca-bentonite as buffer material

    Science.gov (United States)

    Huang, Wei-Hsing; Chen, Wen-Chuan

    2016-04-01

    Swelling behavior is an important criterion in achieving the low-permeability sealing function of buffer material. A potential buffer material may be used for radioactive waste repository in Taiwan is a locally available clayey material known as Zhisin clay, which has been identified as a Ca-bentonite. Due to its Ca-based origin, Zhisin was found to exhibit swelling capacity much lower than that of Na-bentonite. To enhance the swelling potential of Zhisin clay, a cation exchange process by addition of Na2CO3 powder was introduced in this paper. The addition of Na2CO3 reagent to Zhisin clay, in a liquid phase, caused the precipitation of CaCO3 and thereby induced a replacement of Ca2+ ions by Na+ ions on the surface of bentonite. Characterization test conducted on Zhisin clay includes chemical analysis, cation exchange capacity, X-ray diffraction, and thermogravimetry (TG). Free-swelling test apparatus was developed according to International Society of Rock Mechanics recommendations. A series of free-swelling tests were conducted on untreated and activated specimens to characterize the effect of activation on the swelling capacity of Zhisin clay. Efforts were made to determine an optimum dosage for the activation, and to evaluate the aging effect. Also, the activated material was evaluated for its stability in various hydrothermal conditions for potential applications as buffer material in a repository. Experimental results show that Na2CO3-activated Zhisin clay is superior in swelling potential to untreated Zhisin clay. Also, there exists an optimum amount of activator in terms of improvements in the swelling capacity. A distinct time-swell relationship was discovered for activated Zhisin clay. The corresponding mechanism refers to exchange of cations and breakdown of quasi-crystal, which results in ion exchange hysteresis of Ca-bentonite. Due to the ion exchange hysteresis, activated bentonite shows a post-rise time-swell relationship different than the sigmoid

  19. Acoustic waves in granular materials

    NARCIS (Netherlands)

    Mouraille, O.J.P.; Luding, Stefan

    2008-01-01

    Dynamic simulations with discrete elements are used to obtain more insight into the wave propagation in dense granular media. A small perturbation is created on one side of a dense, static packing and examined during its propagation until it arrives at the opposite side. The influence of

  20. Granular materials flow like complex fluids

    Science.gov (United States)

    Kou, Binquan; Cao, Yixin; Li, Jindong; Xia, Chengjie; Li, Zhifeng; Dong, Haipeng; Zhang, Ang; Zhang, Jie; Kob, Walter; Wang, Yujie

    2017-11-01

    Granular materials such as sand, powders and foams are ubiquitous in daily life and in industrial and geotechnical applications. These disordered systems form stable structures when unperturbed, but in the presence of external influences such as tapping or shear they `relax', becoming fluid in nature. It is often assumed that the relaxation dynamics of granular systems is similar to that of thermal glass-forming systems. However, so far it has not been possible to determine experimentally the dynamic properties of three-dimensional granular systems at the particle level. This lack of experimental data, combined with the fact that the motion of granular particles involves friction (whereas the motion of particles in thermal glass-forming systems does not), means that an accurate description of the relaxation dynamics of granular materials is lacking. Here we use X-ray tomography to determine the microscale relaxation dynamics of hard granular ellipsoids subject to an oscillatory shear. We find that the distribution of the displacements of the ellipsoids is well described by a Gumbel law (which is similar to a Gaussian distribution for small displacements but has a heavier tail for larger displacements), with a shape parameter that is independent of the amplitude of the shear strain and of the time. Despite this universality, the mean squared displacement of an individual ellipsoid follows a power law as a function of time, with an exponent that does depend on the strain amplitude and time. We argue that these results are related to microscale relaxation mechanisms that involve friction and memory effects (whereby the motion of an ellipsoid at a given point in time depends on its previous motion). Our observations demonstrate that, at the particle level, the dynamic behaviour of granular systems is qualitatively different from that of thermal glass-forming systems, and is instead more similar to that of complex fluids. We conclude that granular materials can relax

  1. Granular Materials and Risks In ISRU

    Science.gov (United States)

    Behringer, Robert P.; Wilkinson, R. Allen

    2004-01-01

    Working with soil, sand, powders, ores, cement and sintered bricks, excavating, grading construction sites, driving off-road, transporting granules in chutes and pipes, sifting gravel, separating solids from gases, and using hoppers are so routine that it seems straightforward to execute these operations on the Moon and Mars as we do on Earth. We discuss how little these processes are understood and point out the nature of trial-and-error practices that are used in today's massive over-design. Nevertheless, such designs have a high failure rate. Implementation and extensive incremental scaling up of industrial processes are routine because of the inadequate predictive tools for design. We present a number of pragmatic scenarios where granular materials play a role, the risks involved, what some of the basic issues are, and what understanding is needed to greatly reduce the risks. This talk will focus on a particular class of granular flow issues, those that pertain to dense materials, their physics, and the failure problems associated with them. In particular, key issues where basic predictability is lacking include stability of soils for the support of vehicles and facilities, ability to control the flow of dense materials (jamming and flooding/unjamming at the wrong time), the ability to predict stress profiles (hence create reliable designs) for containers such as bunkers or silos. In particular, stress fluctuations, which are not accounted for in standard granular design models, can be very large as granular materials flows, and one result is frequent catastrophic failure of granular devices.

  2. Study on the properties of Gaomiaozi bentonite as the buffer/backfilling materials for HLW disposal

    International Nuclear Information System (INIS)

    Liu Xiaodong; Luo Taian; Zhu Guoping; Chen Qingchun

    2007-12-01

    Systematic studies including mineral composition and structure, physico- chemical properties and thermal properties have been conducted on Gaomiaozi bentonite, Xinghe County, Inner Mongolia Autonomous Region. The compaction characteristics of bentonite and the influence of additive to bentonite have been discussed. The analysis of mineral composition and structure show that the bentonite ores are dominated by montmorillonite. Preliminary studies of the characteristics of ores indicated that No-type bentonite from the deposit has good absorption, excellent swelling and high cation exchangeability. The compressibility of bentonite will be improved by adding the additives such as quartz sand. The studies indicated that the characteristics of Gaomiaozi bentonite can satisfy the requirement of buffer/backfilling materials for HLW repository and the ores can be selected as the preferential candidate to provide buffer/backfill- ing materials for HLW repository in China. (authors)

  3. Study on the properties of Gaomiaozi bentonite as the buffer/backfilling materials for HLW disposal

    Energy Technology Data Exchange (ETDEWEB)

    Xiaodong, Liu [East China Inst. of Technology, Fuzhou (China); [Key Laboratory of Nuclear Resources and Environment of Ministry of Education, Fuzhou (China); Taian, Luo; Guoping, Zhu; Qingchun, Chen [East China Inst. of Technology, Fuzhou (China)

    2007-12-15

    Systematic studies including mineral composition and structure, physico- chemical properties and thermal properties have been conducted on Gaomiaozi bentonite, Xinghe County, Inner Mongolia Autonomous Region. The compaction characteristics of bentonite and the influence of additive to bentonite have been discussed. The analysis of mineral composition and structure show that the bentonite ores are dominated by montmorillonite. Preliminary studies of the characteristics of ores indicated that No-type bentonite from the deposit has good absorption, excellent swelling and high cation exchangeability. The compressibility of bentonite will be improved by adding the additives such as quartz sand. The studies indicated that the characteristics of Gaomiaozi bentonite can satisfy the requirement of buffer/backfilling materials for HLW repository and the ores can be selected as the preferential candidate to provide buffer/backfill- ing materials for HLW repository in China. (authors)

  4. Evaluation for swelling characteristics of buffer and backfill materials for high-level nuclear waste disposal. Influence of sand-bentonite content and cation compositions in bentonite

    International Nuclear Information System (INIS)

    Komine, Hideo; Ogata, Nobuhide

    1999-01-01

    Compacted bentonite and sand-bentonite mixture are attracting greater attention as buffer and backfill materials for disposal pits and access tunnels in the underground facilities for repositories of high-level nuclear waste. Buffer and backfill materials must have the swelling characteristics and are expected to fill up the space between these materials and surrounding ground by swelling. This role is called as 'Self-sealing'. To design the specifications, such as dry density, bentonite content and size, of buffer and backfill materials for the disposal facilities of high-level nuclear wastes described above, we must evaluate the swelling characteristics of compacted bentonite and sand-bentonite mixtures. For this purpose, this study proposed the evaluation formula for swelling characteristics of buffer and backfill materials containing bentonite. This study derived new equations for evaluating the relationship between the swelling deformation of compacted bentonite and sand-bentonite mixtures, and the swelling behavior of montmorillonite minerals, which are swelling clay minerals. This study also proposed new equations for evaluating the ion compositions of bentonite, ion concentration of pore water and the specific surface of bentonite, which significantly influence the swelling characteristics of buffer and backfill materials. The evaluation formula proposed in this study is presented by combining the above-mentioned new equations with theoretical equations, of which are the Gouy-Chapman diffuse double layer theory and the van der Waals force, of repulsive and attractive forces of montmorillonite minerals. (author)

  5. Mathematics and Mechanics of Granular Materials

    CERN Document Server

    Hill, James M

    2005-01-01

    Granular or particulate materials arise in almost every aspect of our lives, including many familiar materials such as tea, coffee, sugar, sand, cement and powders. At some stage almost every industrial process involves a particulate material, and it is usually the cause of the disruption to the smooth running of the process. In the natural environment, understanding the behaviour of particulate materials is vital in many geophysical processes such as earthquakes, landslides and avalanches. This book is a collection of current research from some of the major contributors in the topic of modelling the behaviour of granular materials. Papers from every area of current activity are included, such as theoretical, numerical, engineering and computational approaches. This book illustrates the numerous diverse approaches to one of the outstanding problems of modern continuum mechanics.

  6. Fuzzy batch controller for granular materials

    OpenAIRE

    Zamyatin Nikolaj; Smirnov Gennadij; Fedorchuk Yuri; Rusina Olga

    2018-01-01

    The paper focuses on batch control of granular materials in production of building materials from fluorine anhydrite. Batching equipment is intended for smooth operation and timely feeding of supply hoppers at a required level. Level sensors and a controller of an asynchronous screw drive motor are used to control filling of the hopper with industrial anhydrite binders. The controller generates a required frequency and ensures required productivity of a feed conveyor. Mamdani-type fuzzy infer...

  7. Evaluation on elution feature of bentonite buffer materials

    Energy Technology Data Exchange (ETDEWEB)

    Ishikawa, Hirohisa; Kanno, Takeshi; Matsumoto, Kazuhiro

    1997-09-01

    In order to evaluate long term physical stability of artificial barrier in land disposal of high level radioactive wastes, it is necessary to know quantitatively elution behavior of buffering materials from disposal road (or cavity) to circumferential rock crack. When elution of the buffer material occurs on large scale, amount of bentonite in the disposal road (or cavity) reduces and reduction of various functions expected to the buffer materials is presumed. According to specification examples of road transverse arrangement and disposal vertical arrangement systems, evaluation on elution amount of the buffer materials at disposal environment was conducted. Opening width of rock crack in the disposal environment was supposed to be 0.5 mm. As a result, obtained mass elution ratios of the buffer materials due to extrusion phenomenon were 0.04 to 0.2% after 10,000 year and 2 to 12% after 1,000,000 years. (G.K.)

  8. Bentonite-like material sealing to high-level radioactive wastes storage

    International Nuclear Information System (INIS)

    Linares, J.; Linares Gonzalez, J.; Huertas Garcia, F.; Reyes Camacho.

    1993-01-01

    Among the most used materials for sealing of radioactive waste storage, bentonite shows a high number of advantages because of its plasticity, thermal and hydraulic conductivity, etc. The paper makes a review on different Spanish deposits of bentonite and their stability. Most of studies are focussed on the volcanic region at Cabo de Gata (Almeria). That area offers the most productive hydrothermal bentonite deposits in Spain

  9. Characteristics study of bentonite as candidate of buffer materials for radioactive waste disposal system

    International Nuclear Information System (INIS)

    Suryantoro; Arimuladi, S.P.; Sastrowardoyo, P.B.

    1998-01-01

    Literature studies on bentonite characteristic of, as candidate for radioactive waste disposal system, have been conducted. Several information have been obtained from references, which would be contributed on performance assessment of engineered barrier. The functions bentonite includes the buffering of chemical and physical behavior, i.e. swelling property, self sealing, hydraulic conductivities and gas permeability. This paper also presented long-term stability of bentonite in natural condition related to the illitisazation, which could change its buffering capacities. These information, showed that bentonite was satisfied to be used for candidate of buffer materials in radioactive waste disposal system. (author)

  10. Electrostatics effects in granular materials

    Science.gov (United States)

    Sarkar, Saurabh; Chaudhuri, Bodhisattwa

    2013-06-01

    This purpose of this study is to investigate the role of physiochemical properties and operational conditions in determining the electrostatic interactions between two species on a surface under typical industrial conditions. The variables considered for the study were particle type, particle size and shape, loading mass, surface type, angle of inclination of chute, nature and concentration of additive. Triboelectrification of simple and binary mixtures in a simple hopper and chute geometry was observed to be strongly linked to work function and moisture content of the powdered material.

  11. Sorption of technetium and its analogue rhenium on bentonite material under aerobic conditions

    International Nuclear Information System (INIS)

    Koudelkova, M.; Vinsova, H.; Konirova, R.; Ernestova, M.; Jedinakova-Krizova, V.; Tereesha, M.

    2003-01-01

    The uptake of technetium on bentonite materials has been studied from the point of view of characterization of long-term radioactive elements behavior in nuclear waste repository. Bentonite R (locality Rokle, Czech Republic) and two types of model groundwater (granitic and bentonite) were selected for the sorption experiments. The aim of our research has been to find out the conditions suitable for the technetium sorption on selected bentonite under oxidizing condition. The sorption experiments with Tc-99 on bentonite have been carried out by batch method. The influence of the addition of different materials (e.g. activated carbon, graphite, Fe 2+ ) with bentonite, the effect of solid: aqueous phase ratio and a pH value on the percentage of technetium uptake and on the K d values were tested. Perrhenate was selected as an analogue of pertechnetate in non-active experiments of capillary electrophoresis (CE) and isotachophoresis (ITP). The percentage of rhenium sorbed on bentonite material was determined from the decrease of perrhenate peak area (CE) and from the shortening of the ITP zone corresponding to perrhenate. Both electromigration methods provided comparable results. The results obtained in this study with non-active material were compared to those of technetium acquired by radiometry and polarography. The 8 days kinetics of the perrhenate and pertechnetate sorption on bentonite was described mathematically with a tendency to predict long-term behavior of studied systems. (authors)

  12. BENTONITE-QUARTZ SAND AS THE BACKFILL MATERIALS ON THE RADIOACTIVE WASTE REPOSITORY

    Directory of Open Access Journals (Sweden)

    Raharjo Raharjo

    2010-06-01

    Full Text Available An investigation of the contribution of quartz sand in the bentonite mixture as the backfill materials on the shallow land burial of radioactive waste has been done. The experiment objective is to determine the effect of quartz sand in a bentonite mixture with bentonite particle sizes of -20+40, -40+60, and -60+80 mesh on the retardation factor and the uranium dispersion in the simulation of uranium migration in the backfill materials. The experiment was carried out by the fixed bed method in the column filled by the bentonite mixture with a bentonite-to-quartz sand weight percent ratio of 0/100, 25/75, 50/50, 75/25, and 100/0 on the water saturated condition flown by uranyl nitrate solution at concentration (Co of 500 ppm. The concentration of uranium in the effluents in interval 15 minutes represented as Ct was analyzed by spectrophotometer, then using Co and Ct, retardation factor (R and dispersivity ( were determined. The experiment data showed that the bentonite of -60+80 mesh and the quartz sand of -20+40 mesh on bentonite-to-quartz sand with weight percent ratio of 50/50 gave the highest retardation factor and dispersivity of 18.37 and 0.0363 cm, respectively.   Keywords: bentonite, quartz sand, backfill materials, radioactive waste

  13. Hydrothermal stability of bentonite-based buffer materials

    International Nuclear Information System (INIS)

    Johnston, R.M.; Miller, H.G.

    1985-02-01

    The reactions expected in bentonite-based buffer materials under conditions typical of a nuclear fuel waste disposal include mineral transformations (e.g. smectite to illite; smectite to zeolite) and a range of low-temperature cementation reactions. The probable extent and significance of these reactions are reviewed, and other reactions involving proposed filler sands are also examined briefly. The effects of mineral transformations on buffer performance will be insignificant if disposal vault temperatures do not exceed 100-120 degrees C and pH remains in the range 4 to 8. At pH > 9, zeolitization and silica dissolution may occur and buffer stability cannot be assured. The effects of cementation reactions may be significant, but are difficult to predict and require further investigation

  14. Sorption of technetium and its analogue rhenium on bentonite material under aerobic conditions

    International Nuclear Information System (INIS)

    Vinsova, H.; Koudelkova, M.; Konirova, R.; Vecernik, P.; Jedinakova-Krizova, V.

    2003-01-01

    The uptake of technetium on bentonite materials has been studied from the point of view of characterization of long-term radioactive elements behavior in nuclear waste repository. Bentonite R (locality Rokle, Czech Republic) and two types of model groundwater (granitic and bentonite) were selected for the sorption experiments. It is generally known that bentonite materials show an excellent cation-exchange capacity and, on the other hand, a poor uptake of anions. Technetium occurs under aerobic conditions in its most stable oxidation state (+VII) as pertechnetate, which makes a question of its sorption on bentonite more complex when compared with e.g. Cs + or Sr 2+ . To increase the K d values for technetium sorption on bentonite, it is necessary to carry out the experiments under anaerobic conditions in the presence of reducing agent, which is capable to lower the oxidation state of technetium which enables its successful immobilization. The aim of our research has been to find out the conditions suitable for the technetium sorption on selected bentonite under oxidizing conditions. The sorption experiments with Tc-99 on bentonite have been carried out by batch method. The influence of the addition of different materials (e.g. activated carbon, graphite, Fe 2+ , Fe) with bentonite, the effect of solid:aqueous phase ratio and a pH value on the percentage of technetium uptake and on the K d values were tested. Perrhenate was selected as an analogue of pertechnetate in non-active experiments of capillary electrophoresis (CE) and isotachophoresis (ITP). The percentage of rhenium sorbed on bentonite material was determined from the decrease of perrhenate peak area (CE) and from the shortening of the ITP zone corresponding to perrhenate. Both electromigration methods provided comparable results. The results obtained in this study with non-active material were compared to those of technetium acquired by radiometry and polarography. (authors)

  15. Fuzzy batch controller for granular materials

    Directory of Open Access Journals (Sweden)

    Zamyatin Nikolaj

    2018-01-01

    Full Text Available The paper focuses on batch control of granular materials in production of building materials from fluorine anhydrite. Batching equipment is intended for smooth operation and timely feeding of supply hoppers at a required level. Level sensors and a controller of an asynchronous screw drive motor are used to control filling of the hopper with industrial anhydrite binders. The controller generates a required frequency and ensures required productivity of a feed conveyor. Mamdani-type fuzzy inference is proposed for controlling the speed of the screw that feeds mixture components. As related to production of building materials based on fluoride anhydrite, this method is used for the first time. A fuzzy controller is proven to be effective in controlling the filling level of the supply hopper. In addition, the authors determined optimal parameters of the batching process to ensure smooth operation and production of fluorine anhydrite materials of specified properties that can compete with gypsum-based products.

  16. Experimental investigations of piping phenomena in bentonite based buffer material

    International Nuclear Information System (INIS)

    Suzuki, K.; Asano, H.; Kobayashi, I.; Sellin, P.; Svemar, C.; Holmqvist, M.

    2012-01-01

    Document available in extended abstract form only. Formation of channels in a clay based buffer material is often referred to as 'piping'. Piping is likely to occur in bentonite based buffer materials in a fractured host rock during the early evolution of the repository when strong hydraulic gradients are present. After water saturation of the repository and reestablishment of the hydraulic gradients piping will not be an issue. However, piping in the early phase may still have implications for long-term performance: 1. if the pipes fail to close there may be remaining conductive pathways in the engineered barrier, and 2. piping may lead to erosion or redistribution of material which needs to be taken into account in the long-term performance assessment. This means that the piping process may affect requirements on rock characterization, water inflow and water management during the installation phase, buffer material properties and buffer installation methodology. As a part of the 'Bentonite re-saturation' program, RWMC has initiated and performed studies of the piping process. The main objectives of the studies are to answer: 1. Under what conditions can pipes form? 2. How do pipes evolve with time? 3. When and how do pipes close/reseal? 4. How does piping affect the buffer properties? 5. How much mass can be lost by erosion? The answers will be used in the development of the requirements stated above as well as input to long term performance assessments. overview of the experiment Test apparatuses were manufactured for investigation of the piping phenomena, see Figure 1. The apparatuses have drainage gutter to prevent clogging to take place with eroded material, and to keep an advection field around specimens. There is also a storage chamber for eroded material on the apparatuses. In the investigation, specimens of bentonite block and pellets were used. The block specimen consisted of a mixture of Japanese Na type bentonite, termed Kunigel V1, and 30 wt% silica

  17. Resilient Modulus Characterization of Alaskan Granular Base Materials

    Science.gov (United States)

    2010-08-01

    Resilient modulus (MR) of base course material is an important material input for : pavement design. In Alaska, due to distinctiveness of local climate, material source, : fines content and groundwater level, resilient properties of D-1 granular base...

  18. A hydrodynamic model for granular material flows including segregation effects

    Science.gov (United States)

    Gilberg, Dominik; Klar, Axel; Steiner, Konrad

    2017-06-01

    The simulation of granular flows including segregation effects in large industrial processes using particle methods is accurate, but very time-consuming. To overcome the long computation times a macroscopic model is a natural choice. Therefore, we couple a mixture theory based segregation model to a hydrodynamic model of Navier-Stokes-type, describing the flow behavior of the granular material. The granular flow model is a hybrid model derived from kinetic theory and a soil mechanical approach to cover the regime of fast dilute flow, as well as slow dense flow, where the density of the granular material is close to the maximum packing density. Originally, the segregation model has been formulated by Thornton and Gray for idealized avalanches. It is modified and adapted to be in the preferred form for the coupling. In the final coupled model the segregation process depends on the local state of the granular system. On the other hand, the granular system changes as differently mixed regions of the granular material differ i.e. in the packing density. For the modeling process the focus lies on dry granular material flows of two particle types differing only in size but can be easily extended to arbitrary granular mixtures of different particle size and density. To solve the coupled system a finite volume approach is used. To test the model the rotational mixing of small and large particles in a tumbler is simulated.

  19. Enhanced shear strength of sodium bentonite using frictional additives

    International Nuclear Information System (INIS)

    Schmitt, K.E.; Bowders, J.J.; Gilbert, R.B.; Daniel, D.E.

    1997-01-01

    One of the most important obstacles to using geosynthetic clay liners (GCLs) in landfill cover systems is the low shear strength provided by the bentonitic portion of the GCL. In this study, the authors propose that granular, frictional materials might be added to the bentonite to form an admixture that would have greater shear strength than the bentonite alone while still raining low hydraulic conductivity. Bentonite was mixed with two separate granular additives, expanded shale and recycled to form mixtures consisting of 20-70% bentonite by weight. In direct shear tests at normal stresses of 34.5-103.5 kPa, effective friction angles were measured as 45 degrees for the expanded 36 degrees for the recycled glass, and 7 degrees for the hydrated granular bentonite. The strength of the expanded shale mixtures increased nearly linearly as the percentage shale in the mixture increased, to 44 degrees for a bentonite mixture with 80% shale. The addition of recycled glass showed little effect on the shear strength of the mixtures of glass and bentonite. Hydraulic conductivity measurements for both types of mixtures indicated a linear increase with log(k) as the amount of granular additive increased. For applications involving geosynthetic clay liners for cover systems, a mixture of 40% expanded shale and 60% bentonite is recommended, although further testing must be done. The 40/60 mixture satisfies the hydraulic equivalency requirement, with k = 5.1X10 -9 cm/sec, while increasing the shear strength parameters of the bentonitic mixture to φ' = 17 degrees and c' = 0

  20. Friction law and hysteresis in granular materials

    Science.gov (United States)

    DeGiuli, E.; Wyart, M.

    2017-08-01

    The macroscopic friction of particulate materials often weakens as the flow rate is increased, leading to potentially disastrous intermittent phenomena including earthquakes and landslides. We theoretically and numerically study this phenomenon in simple granular materials. We show that velocity weakening, corresponding to a nonmonotonic behavior in the friction law, μ(I), is present even if the dynamic and static microscopic friction coefficients are identical, but disappears for softer particles. We argue that this instability is induced by endogenous acoustic noise, which tends to make contacts slide, leading to faster flow and increased noise. We show that soft spots, or excitable regions in the materials, correspond to rolling contacts that are about to slide, whose density is described by a nontrivial exponent θs. We build a microscopic theory for the nonmonotonicity of μ(I), which also predicts the scaling behavior of acoustic noise, the fraction of sliding contacts χ, and the sliding velocity, in terms of θs. Surprisingly, these quantities have no limit when particles become infinitely hard, as confirmed numerically. Our analysis rationalizes previously unexplained observations and makes experimentally testable predictions.

  1. Friction law and hysteresis in granular materials.

    Science.gov (United States)

    DeGiuli, E; Wyart, M

    2017-08-29

    The macroscopic friction of particulate materials often weakens as the flow rate is increased, leading to potentially disastrous intermittent phenomena including earthquakes and landslides. We theoretically and numerically study this phenomenon in simple granular materials. We show that velocity weakening, corresponding to a nonmonotonic behavior in the friction law, [Formula: see text], is present even if the dynamic and static microscopic friction coefficients are identical, but disappears for softer particles. We argue that this instability is induced by endogenous acoustic noise, which tends to make contacts slide, leading to faster flow and increased noise. We show that soft spots, or excitable regions in the materials, correspond to rolling contacts that are about to slide, whose density is described by a nontrivial exponent [Formula: see text] We build a microscopic theory for the nonmonotonicity of [Formula: see text], which also predicts the scaling behavior of acoustic noise, the fraction of sliding contacts [Formula: see text], and the sliding velocity, in terms of [Formula: see text] Surprisingly, these quantities have no limit when particles become infinitely hard, as confirmed numerically. Our analysis rationalizes previously unexplained observations and makes experimentally testable predictions.

  2. Jetting and flooding of granular backfill materials : [summary].

    Science.gov (United States)

    2015-03-01

    Granular backfill materials on highway projects are often compacted by mechanical methods. : This requires the contractor to place backfill material into loose lifts of varying thickness : and use compaction equipment to reduce air voids and increase...

  3. Salt content impact on the unsaturated property of bentonite-sand buffer backfilling materials

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Ming [Key Laboratory of Mechanics on Disaster and Environment in Western China, Lanzhou University, Lanzhou 730000 (China); Zhang Huyuan, E-mail: p1314lvp@yahoo.com.cn [Key Laboratory of Mechanics on Disaster and Environment in Western China, Lanzhou University, Lanzhou 730000 (China); Jia Lingyan; Cui Suli [Key Laboratory of Mechanics on Disaster and Environment in Western China, Lanzhou University, Lanzhou 730000 (China)

    2012-09-15

    Highlights: Black-Right-Pointing-Pointer SWCC and infiltration process of bentonite-sand mixtures is researched. Black-Right-Pointing-Pointer The k{sub u} of bentonite-sand mixtures was evaluated as the buffer backfilling materials. Black-Right-Pointing-Pointer Salt content impacting on the unsaturated property of bentonite-sand materials is small. - Abstract: Bentonite mixed with sand is often considered as possible engineered barrier in deep high-level radioactive waste disposal in China. In the present work, the vapor transfer technique and water infiltration apparatus were used to measure the soil water characteristic curve (SWCC) and unsaturated hydraulic conductivity (k{sub u}) of bentonite-sand mixtures (B/S) effected by salt content. Results show, the water-holding capacity and k{sub u} increase slightly with the concentration of Na{sup +} in pore liquid increasing from 0 g/L to 12 g/L, similar with the solution concentration of Beishan groundwater in China. Salt content in the laboratory produced only one order of magnitude increase in k{sub u}, which is the 'safe' value. The different pore liquid concentrations used in this study led to small differences in thickness of diffuse double layer of bentonite in mixtures, this might explain why some differences have been found in final values of k{sub u}.

  4. On the hydro-mechanical behaviour of MX80 bentonite-based materials

    Directory of Open Access Journals (Sweden)

    Yu-Jun Cui

    2017-06-01

    Full Text Available Bentonite-based materials have been considered in many countries as engineered barrier/backfilling materials in deep geological disposal of high-level radioactive waste. During the long period of waste storage, these materials will play an essential role in ensuring the integrity of the storage system that consists of the waste canisters, the engineered barrier/backfill, the retaining structures as well as the geological barrier. Thus, it is essential to well understand the hydro-mechanical behaviours of these bentonite-based materials. This review paper presents the recent advances of knowledge on MX80 bentonite-based materials, in terms of water retention properties, hydraulic behaviour and mechanical behaviour. Emphasis is put on the effect of technological voids and the role of the dry density of bentonite. The swelling anisotropy is also discussed based on the results from swelling tests with measurements of both axial and radial swelling pressures on a sand-bentonite mixture compacted at different densities. Microstructure observation was used to help the interpretation of macroscopic hydro-mechanical behaviour. Also, the evolution of soil microstructure thus the soil density over time is discussed based on the results from mock-up tests. This evolution is essential for understanding the long-term hydro-mechanical behaviour of the engineered barrier/backfill.

  5. Penetration in bimodal, polydisperse granular material

    KAUST Repository

    Kouraytem, Nadia; Thoroddsen, Sigurdur T; Marston, J. O.

    2016-01-01

    We investigate the impact penetration of spheres into granular media which are compositions of two discrete size ranges, thus creating a polydisperse bimodal material. We examine the penetration depth as a function of the composition (volume fractions of the respective sizes) and impact speed. Penetration depths were found to vary between delta = 0.5D(0) and delta = 7D(0), which, for mono-modal media only, could be correlated in terms of the total drop height, H = h + delta, as in previous studies, by incorporating correction factors for the packing fraction. Bimodal data can only be collapsed by deriving a critical packing fraction for each mass fraction. The data for the mixed grains exhibit a surprising lubricating effect, which was most significant when the finest grains [d(s) similar to O(30) mu m] were added to the larger particles [d(l) similar to O(200 - 500) mu m], with a size ratio, epsilon = d(l)/d(s), larger than 3 and mass fractions over 25%, despite the increased packing fraction. We postulate that the small grains get between the large grains and reduce their intergrain friction, only when their mass fraction is sufficiently large to prevent them from simply rattling in the voids between the large particles. This is supported by our experimental observations of the largest lubrication effect produced by adding small glass beads to a bed of large sand particles with rough surfaces.

  6. Penetration in bimodal, polydisperse granular material

    KAUST Repository

    Kouraytem, N.

    2016-11-07

    We investigate the impact penetration of spheres into granular media which are compositions of two discrete size ranges, thus creating a polydisperse bimodal material. We examine the penetration depth as a function of the composition (volume fractions of the respective sizes) and impact speed. Penetration depths were found to vary between delta = 0.5D(0) and delta = 7D(0), which, for mono-modal media only, could be correlated in terms of the total drop height, H = h + delta, as in previous studies, by incorporating correction factors for the packing fraction. Bimodal data can only be collapsed by deriving a critical packing fraction for each mass fraction. The data for the mixed grains exhibit a surprising lubricating effect, which was most significant when the finest grains [d(s) similar to O(30) mu m] were added to the larger particles [d(l) similar to O(200 - 500) mu m], with a size ratio, epsilon = d(l)/d(s), larger than 3 and mass fractions over 25%, despite the increased packing fraction. We postulate that the small grains get between the large grains and reduce their intergrain friction, only when their mass fraction is sufficiently large to prevent them from simply rattling in the voids between the large particles. This is supported by our experimental observations of the largest lubrication effect produced by adding small glass beads to a bed of large sand particles with rough surfaces.

  7. Wyoming bentonites. Evidence from the geological record to evaluate the suitability of bentonite as a buffer material during the long-term underground containment of radioactive wastes

    International Nuclear Information System (INIS)

    Smellie, J.

    2001-12-01

    In the Swedish programme for the deep, geological disposal of radioactive wastes, bentonite is planned to be used as a barrier material to reduce groundwater flow and minimise radionuclide migration into the geosphere. One of the possible threats to long-term bentonite stability is the gradual incursion of saline water into the repository confines which may reduce the swelling capacity of the bentonite, even to the extent of eliminating the positive effects of mixing bentonite into backfill materials. Important information may be obtained from the study of analogous processes in nature (i.e. natural analogue or natural system studies) where bentonite, during its formation, has been in long-term contact with reducing waters of brackish to saline character. Type bentonites include those mined from the Clay Spur bed at the top of the Cretaceous Mowry Formation in NE Wyoming and demarcated for potential use as a barrier material (e.g. MX-80 sodium bentonite) in the Swedish radioactive waste programme. This bentonite forms part of the Mowry Shale which was deposited in a southern embayment of the late Albian Western Interior Cretaceous sea (Mowry Sea). The question is whether these bentonite deposits show evidence of post-deposition alteration caused by the sea water in which they were deposited, and/or, have they been altered subsequently by contact with waters of increasing salinity? Bentonites are the product of pyroclastic fall deposits thought to be generated by the type of explosive, subaerial volcanic activity characteristic of Plinian eruptive systems. In Wyoming the overall composition of the original ash varied from dacite to rhyolite, or latite to trachyte. The ash clouds were carried to high altitudes and eastwards by the prevailing westerly winds before falling over the shallow Mowry Sea and forming thin but widespread and continuous horizons on sea floor muds and sands. Whilst bentonites were principally wind-transported, there is evidence of some water

  8. Wyoming bentonites. Evidence from the geological record to evaluate the suitability of bentonite as a buffer material during the long-term underground containment of radioactive wastes

    Energy Technology Data Exchange (ETDEWEB)

    Smellie, J [Conterra AB (Sweden)

    2001-12-01

    In the Swedish programme for the deep, geological disposal of radioactive wastes, bentonite is planned to be used as a barrier material to reduce groundwater flow and minimise radionuclide migration into the geosphere. One of the possible threats to long-term bentonite stability is the gradual incursion of saline water into the repository confines which may reduce the swelling capacity of the bentonite, even to the extent of eliminating the positive effects of mixing bentonite into backfill materials. Important information may be obtained from the study of analogous processes in nature (i.e. natural analogue or natural system studies) where bentonite, during its formation, has been in long-term contact with reducing waters of brackish to saline character. Type bentonites include those mined from the Clay Spur bed at the top of the Cretaceous Mowry Formation in NE Wyoming and demarcated for potential use as a barrier material (e.g. MX-80 sodium bentonite) in the Swedish radioactive waste programme. This bentonite forms part of the Mowry Shale which was deposited in a southern embayment of the late Albian Western Interior Cretaceous sea (Mowry Sea). The question is whether these bentonite deposits show evidence of post-deposition alteration caused by the sea water in which they were deposited, and/or, have they been altered subsequently by contact with waters of increasing salinity? Bentonites are the product of pyroclastic fall deposits thought to be generated by the type of explosive, subaerial volcanic activity characteristic of Plinian eruptive systems. In Wyoming the overall composition of the original ash varied from dacite to rhyolite, or latite to trachyte. The ash clouds were carried to high altitudes and eastwards by the prevailing westerly winds before falling over the shallow Mowry Sea and forming thin but widespread and continuous horizons on sea floor muds and sands. Whilst bentonites were principally wind-transported, there is evidence of some water

  9. Review of the properties and uses of bentonite as a buffer and backfill material

    International Nuclear Information System (INIS)

    Savage, D.; Lind, A.; Arthur, R.C.

    1999-05-01

    Research carried out by SKB on the use and behaviour of bentonite as a buffer and backfill material in a radioactive waste repository has been reviewed. The following research areas have been evaluated: mechanical properties; hydraulic and other transport properties; geochemical properties; thermal properties and resaturation; gas migration; manufacturing and emplacement procedures. This review has shown that SKB has carried out much pioneering and world-leading research on bentonite, particularly with regard to analogue studies, microtextural work and practical manufacturing and emplacement procedures. However, there are a number of subject areas which appear less well addressed than others which require further attention: The extrapolation of experimental results of the mechanical properties of bentonite to repository timescales and repository conditions should be investigated further. There is a need for detailed microstructural analysis of materials as part of experimental programmes. This would enable SKB to build confidence in the interpretations of results and reveal whether the mechanical processes occurring during experimentation truly reflect expectations of the performance of the repository. The large amount of experimental, theoretical, empirical datasets and computer models of the mechanical properties of bentonite need to be collated to form a database which is assessable and relevant to those involved in performance assessment calculations. At present, the valuable results of many excellent research projects on mechanical properties of bentonite buffer are not readily available. There seems to be a relatively poor understanding of the mechanisms of radionuclide diffusion through compacted bentonite. Other international work suggests that diffusion coefficients are much lower than those applied by SKB in its PA work. The importance of surface diffusion to describe diffusion in bentonite for certain chemical species ascribed by SKB is not reflected in

  10. Review of the properties and uses of bentonite as a buffer and backfill material

    Energy Technology Data Exchange (ETDEWEB)

    Savage, D.; Lind, A. [QuantiSci Ltd., Melton Mowbray (United Kingdom); Arthur, R.C. [QuantiSci lnc., Denver, CO (United States)

    1999-05-01

    Research carried out by SKB on the use and behaviour of bentonite as a buffer and backfill material in a radioactive waste repository has been reviewed. The following research areas have been evaluated: mechanical properties; hydraulic and other transport properties; geochemical properties; thermal properties and resaturation; gas migration; manufacturing and emplacement procedures. This review has shown that SKB has carried out much pioneering and world-leading research on bentonite, particularly with regard to analogue studies, microtextural work and practical manufacturing and emplacement procedures. However, there are a number of subject areas which appear less well addressed than others which require further attention: The extrapolation of experimental results of the mechanical properties of bentonite to repository timescales and repository conditions should be investigated further. There is a need for detailed microstructural analysis of materials as part of experimental programmes. This would enable SKB to build confidence in the interpretations of results and reveal whether the mechanical processes occurring during experimentation truly reflect expectations of the performance of the repository. The large amount of experimental, theoretical, empirical datasets and computer models of the mechanical properties of bentonite need to be collated to form a database which is assessable and relevant to those involved in performance assessment calculations. At present, the valuable results of many excellent research projects on mechanical properties of bentonite buffer are not readily available. There seems to be a relatively poor understanding of the mechanisms of radionuclide diffusion through compacted bentonite. Other international work suggests that diffusion coefficients are much lower than those applied by SKB in its PA work. The importance of surface diffusion to describe diffusion in bentonite for certain chemical species ascribed by SKB is not reflected in

  11. Editorial: Modelling and computational challenges in granular materials

    OpenAIRE

    Weinhart, Thomas; Thornton, Anthony Richard; Einav, Itai

    2015-01-01

    This is the editorial for the special issue on “Modelling and computational challenges in granular materials” in the journal on Computational Particle Mechanics (CPM). The issue aims to provide an opportunity for physicists, engineers, applied mathematicians and computational scientists to discuss the current progress and latest advancements in the field of advanced numerical methods and modelling of granular materials. The focus will be on computational methods, improved algorithms and the m...

  12. An automata model of granular materials

    International Nuclear Information System (INIS)

    Gutt, G.M.; Haff, P.K.

    1990-01-01

    In this paper a new modeling technique (the Lattice Grain Model) is presented for the simulation of two-dimensional granular systems involving large numbers of grains. These granular systems may include both high shear rate regions as well as static plugs of grains and cannot easily be handled within the framework of existing continuum theories such as soil mechanics. The Lattice Grain Model (LGrM) is similar to the Lattice Gas Model (LBM). This allows large simulations to be programmed onto a hypercube concurrent processor in a straightforward manner. However, it differs from LBM in that it includes the inelastic collisions and volume-filling properties of macroscopic grains. Examples to be presented will include Couette flow, flow through an hourglass, and gravity-driven flows around obstacles

  13. Mineralogy and sealing properties of various bentonites and smectite-rich clay materials

    Energy Technology Data Exchange (ETDEWEB)

    Karnland, Ola; Olsson, Siv; Nilsson, Ulf (Clay Technology AB (SE))

    2006-12-15

    The present work includes a coherent study of Wyoming bentonite with respect to the most relevant properties for use in a repository, and a parallel study of other potential buffer and tunnel backfilling materials. The reason for this is twofold; to quantify the effect of mineralogical variations on the various important sealing properties of bentonite, and to verify that there are alternative potential sources of bentonite. The latter is motivated by the fact that Sweden alone plans to deposit at least 6,000 copper canisters which include approximately 130,000 metric tones bentonite buffer material and several times more as tunnel backfill material. Different types of sealing clay materials may also be relevant to use, since the demands on the clay will be different at the various locations in a repository. Alternative sources of bentonite would consequently be valuable in order to secure quality, supply, and price. Important aspects on buffer and tunnel backfilling materials may be summarized as: Original sealing properties. Hazardous substances in any respect. Short-term effects of ground-water chemistry. Long-term stability, i.e. effects of temperature and ground-water chemistry. Availability. Costs. The focus in this study is on the first three items. The long-term stability is indirectly considered in that mineralogical composition is determined. The availability is only considered in such a way that most of the analyzed materials represent huge clay formations, which contain much more material than needed for a repository. The cost aspects have not been included, mainly because the present day price is not relevant due to the time frame of the construction of a repository

  14. Flowability of granular materials with industrial applications - An experimental approach

    Science.gov (United States)

    Torres-Serra, Joel; Romero, Enrique; Rodríguez-Ferran, Antonio; Caba, Joan; Arderiu, Xavier; Padullés, Josep-Manel; González, Juanjo

    2017-06-01

    Designing bulk material handling equipment requires a thorough understanding of the mechanical behaviour of powders and grains. Experimental characterization of granular materials is introduced focusing on flowability. A new prototype is presented which performs granular column collapse tests. The device consists of a channel whose design accounts for test inspection using visualization techniques and load measurements. A reservoir is attached where packing state of the granular material can be adjusted before run-off to simulate actual handling conditions by fluidisation and deaeration of the pile. Bulk materials on the market, with a wide range of particle sizes, can be tested with the prototype and the results used for classification in terms of flowability to improve industrial equipment selection processes.

  15. Modelling of Granular Materials Using the Discrete Element Method

    DEFF Research Database (Denmark)

    Ullidtz, Per

    1997-01-01

    With the Discrete Element Method it is possible to model materials that consists of individual particles where a particle may role or slide on other particles. This is interesting because most of the deformation in granular materials is due to rolling or sliding rather that compression of the gra...

  16. Frost susceptibility of granular subbase materials contaminated by deicing chemicals

    DEFF Research Database (Denmark)

    Jørgensen, Anders Stuhr; Orlander, Tobias; Doré, Guy

    2013-01-01

    The increase in urban population in arctic areas leads to an increased demand for transportation infrastructures (such as roads and airfields) in the regions. This challenges the road constructions in terms of condition, bearing capacity and maintenance. It is believed that deicing agents used...... on roads and airfields enter the granular subbase materials and thereby makes the soil more frost-susceptible. In this project a series of isothermal frost heave tests has been carried out on granular subbase material from the runway at Kuujjuaq Airport, Québec, Canada. The tests have been carried out...

  17. Sealing of boreholes using natural, compatible materials: Granular salt

    International Nuclear Information System (INIS)

    Finley, R.E.; Zeuch, D.H.; Stormont, J.C.; Daemen, J.J.K.

    1994-01-01

    Granular salt can be used to construct high performance permanent seals in boreholes which penetrate rock salt formations. These seals are described as seal systems comprised of the host rock, the seal material, and the seal rock interface. The performance of these seal systems is defined by the complex interactions between these seal system components through time. The interactions are largely driven by the creep of the host formation applying boundary stress on the seal forcing host rock permeability with time. The immediate permeability of these seals is dependent on the emplaced density. Laboratory test results suggest that careful emplacement techniques could results in immediate seal system permeability on the order of 10 -16 m 2 to 10 -18 m 2 (10 -4 darcy to 10 -6 ). The visco-plastic behavior of the host rock coupled with the granular salts ability to ''heal'' or consolidate make granular salt an ideal sealing material for boreholes whose permanent sealing is required

  18. Development and implementation of a quality control system for bentonite materials

    International Nuclear Information System (INIS)

    Kiviranta, Leena; Schatz, Timothy; Autio, Jorma; Korkeakoski, Petri

    2010-01-01

    Document available in extended abstract form only. This work describes the development and implementation of a quality control system for bentonite material from initial acquisition to processing. The system is designed to provide an efficient, cost-effective, and reliable means of ensuring the sufficient quality of bentonite destined for use in the engineered barrier system of a repository for spent nuclear fuel. The program is outlined and includes three test categories: Basic Acceptance Testing, Advanced Acceptance Testing, and Complementary Testing. Basic acceptance testing is to be performed for any and all bentonite material considered for use in the repository. These tests are designed to quickly determine whether the material meets at least a basic level of acceptance. If the material passes basic acceptance testing, it progresses to the advanced acceptance testing regime. If the acquired material originates over multiple source lots, basic and advanced acceptance testing are performed for each. Complementary testing is performed when necessary or requested. B plus Tech has developed the in-house capability and competence to perform the majority of the tests and built a network (in Finland) of reliable, external partners and providers for the remainder. (authors)

  19. Mechanics of Granular Materials : Constitutive Behavior and Pattern Transformation

    NARCIS (Netherlands)

    Göncü, F.

    2012-01-01

    From pharmaceutical to mining or traveling desert dunes to earthquakes, granular materials are at the heart of many industries and natural phenomena. Improving the efficiency of the machines handling them or, constructing safer buildings requires a critical understanding of their behavior. However,

  20. Statics and kinematics of discrete Cosserat-type granular materials

    NARCIS (Netherlands)

    Kruyt, Nicolaas P.

    2003-01-01

    A theoretical framework is presented for the statics and kinematics of discrete Cosserat-type granular materials. In analogy to the force and moment equilibrium equations for particles, compatibility equations for closed loops are formulated in the two-dimensional case for relative displacements and

  1. Martian gullies: possible formation mechanism by dry granular material..

    Science.gov (United States)

    Cedillo-Flores, Y.; Durand-Manterola, H. J.

    section Some of the geomorphological features in Mars are the gullies Some theories developed tried explain its origin either by liquid water liquid carbon dioxide or flows of dry granular material We made a comparative analysis of the Martian gullies with the terrestrial ones We propose that the mechanism of formation of the gullies is as follows In winter CO 2 snow mixed with sand falls in the terrain In spring the CO 2 snow sublimate and gaseous CO 2 make fluid the sand which flows like liquid eroding the terrain and forming the gullies By experimental work with dry granular material we simulated the development of the Martian gullies injecting air in the granular material section We present the characteristics of some terrestrial gullies forms at cold environment sited at Nevado de Toluca Volcano near Toluca City M e xico We compare them with Martian gullies choose from four different areas to target goal recognize or to distinguish to identify possible processes evolved in its formation Also we measured the lengths of those Martian gullies and the range was from 24 m to 1775 meters Finally we present results of our experimental work at laboratory with dry granular material

  2. Non-Steady Oscillatory Flow in Coarse Granular Materials

    DEFF Research Database (Denmark)

    Andersen, O. H.; Gent, M. R. A. van; Meer, J. W. van der

    1992-01-01

    Stationary and oscillatory flow through coarse granular materials have been investigated experimentally at Delft Hydraulics in their oscillating water tunnel with the objective of determining the coefficients of the extended Forchheimer equation. Cylinders, spheres and different types of rock have....... Further, for the non-stationary term, the virtual mass coefficient will be derived....

  3. Rheological Behavior of Dense Assemblies of Granular Materials

    International Nuclear Information System (INIS)

    Sundaresan, Sankaran; Tardos, Gabriel I.; Subramaniam, Shankar

    2011-01-01

    Assemblies of granular materials behave differently when they are owing rapidly, from when they are slowly deforming. The behavior of rapidly owing granular materials, where the particle-particle interactions occur largely through binary collisions, is commonly related to the properties of the constituent particles through the kinetic theory of granular materials. The same cannot be said for slowly moving or static assemblies of granular materials, where enduring contacts between particles are prevalent. For instance, a continuum description of the yield characteristics of dense assemblies of particles in the quasistatic ow regime cannot be written explicitly on the basis of particle properties, even for cohesionless particles. Continuum models for this regime have been proposed and applied, but these models typically assume that the assembly is at incipient yield and they are expressed in terms of the yield function, which we do not yet know how to express in terms of particle-level properties. The description of the continuum rheology in the intermediate regime is even less understood. Yet, many practically important flows in nature and in a wide range of technological applications occur in the dense flow regime and at the transition between dilute and dense regimes; the lack of validated continuum rheological models for particle assemblies in these regimes limits predictive modeling of such flows. This research project is aimed at developing such rheological models.

  4. Discrete Element study of granular material - Bumpy wall interface behavior

    Science.gov (United States)

    El Cheikh, Khadija; Rémond, Sébastien; Pizette, Patrick; Vanhove, Yannick; Djelal, Chafika

    2016-09-01

    This paper presents a DEM study of a confined granular material sheared between two parallel bumpy walls. The granular material consists of packed dry spherical particles. The bumpiness is modeled by spheres of a given diameter glued on horizontal planes. Different bumpy surfaces are modeled by varying diameter or concentration of glued spheres. The material is sheared by moving the two bumpy walls at fixed velocity. During shear, the confining pressure applied on each bumpy wall is controlled. The effect of wall bumpiness on the effective friction coefficient and on the granular material behavior at the bumpy walls is reported for various shearing conditions. For given bumpiness and confining pressure that we have studied, it is found that the shear velocity does not affect the shear stress. However, the effective friction coefficient and the behavior of the granular material depend on the bumpiness. When the diameter of the glued spheres is larger than about the average grains diameter of the medium, the latter is uniformly sheared and the effective friction coefficient remains constant. For smaller diameters of the glued spheres, the effective friction coefficient increases with the diameter of glued spheres. The influence of glued spheres concentration is significant only for small glued spheres diameters, typically half of average particle diameter of the granular material. In this case, increasing the concentration of glued spheres leads to a decrease in effective friction coefficient and to shear localization at the interface. For different diameters and concentrations of glued spheres, we show that the effect of bumpiness on the effective friction coefficient can be characterized by the depth of interlocking.

  5. Consideration of reinforcement mechanism in the short fiber mixing granular materials by granular element simulations

    Science.gov (United States)

    Mori, Kentaro; Kaneko, Kenji; Hashizume, Yutaka

    2017-06-01

    The short fiber mixing method is well known as one of the method to improve the strength of gran- ular soils in geotechnical engineering. Mechanical properties of the short fiber mixing granular materials are influenced by many factors, such as the mixture ratio of the short fiber, the material of short fiber, the length, and the orientation. In particular, the mixture ratio of the short fibers is very important in mixture design. In the past study, we understood that the strength is reduced by too much short fiber mixing by a series of tri-axial compression experiments. Namely, there is "optimum mixture ratio" in the short fiber mixing granular soils. In this study, to consider the mechanism of occurrence of the optimum mixture ratio, we carried out the numerical experiments by granular element method. As the results, we can understand that the strength decrease when too much grain-fiber contact points exist, because a friction coefficient is smaller than the grain-grain contact points.

  6. Preparation of Fe3O4/Bentonite Nanocomposite from Natural Iron Sand by Co-precipitation Method for Adsorbents Materials

    Science.gov (United States)

    Sebayang, Perdamean; Kurniawan, Candra; Aryanto, Didik; Arief Setiadi, Eko; Tamba, Konni; Djuhana; Sudiro, Toto

    2018-03-01

    An adsorption method is one of the effective ways to filter the heavy metals wastes in aqueous system. In this paper, the Fe3O4/bentonite nanocomposites were successfully prepared from natural iron sand by co-precipitation method. The chemical process was carried out by dissolving and hot stirring the milled iron sand and bentonite in acid solution and precipitating it by NH4OH. The sediment was then washed using distilled water to neutralize pH and dried at 100 °C for 5 hours to produce Fe3O4/bentonite powders. The samples were characterized by XRD, FTIR, BET, TEM, VSM and AAS. All samples were composed by Fe3O4 single phase with a spinnel structure and lattice parameter of 8.373 Å. The transmittance peak of FTIR curve proved that the Fe3O4 particles and bentonite had a molecular bonding. The addition of bentonite to Fe3O4 nanoparticles generally reduced the magnetic properties of Fe3O4/bentonite nanocomposites. The optimum condition of 30 wt% bentonite resulted 105.9 m2/g in surface area, 14 nm in an average particle size and 3.2 nm in pore size. It can be used as Cu and Pb adsorbent materials.

  7. Characterisation of bentonites from Kutch, India and Milos, Greece - some candidate tunnel back-fill materials?

    International Nuclear Information System (INIS)

    Olsson, Siv; Karnland, Ola

    2009-12-01

    During the past decades comprehensive investigations have been made on bentonite clays in order to find optimal components of the multi-barrier system of repositories for radioactive waste. The present study gives a mineralogical characterisation of some selected bentonites, in order to supply some of the necessary background data on the bentonites for evaluating their potential as tunnel back-fill materials. Two bentonites from the island of Milos, Greece (Milos BF 04 and BF 08), and two bentonites from Kutch, India (Kutch BF 04 and BF 08) were analysed for their grain size distribution, cation exchange properties and chemical composition. The mineralogical composition was determined by X-ray diffraction analysis and evaluated quantitatively by use of the Siroquant software. Both the bulk bentonite and the 63 μm. The bentonite is distinguished by a high content of dolomite and calcite, which make up almost 25% of the bulk sample. The major accessory minerals are K-feldspars and plagioclase, whereas the content of sulphur-bearing minerals is very low (0.06% total S). Smectite makes up around 60% of the bulk sample, which has a CEC value of 73 meq/100 g. The pool of interlayer cations has a composition Mg>Ca>>Na>>K. The X-ray diffraction characteristics and the high potassium content (1.03% K 2 O) of the Na>Mg>>K. The 2 O) which indicates that also this smectite may be interstratified with a few percent illitic layers. Based on the charge distribution the smectite should be classified as montmorillonite but in this case Fe predominates over Mg in the octahedral sheet. The structural formula suggests that this smectite has the lowest total layer charge of the smectites examined. Kutch BF 04 contains essentially no particles >63 μm. The bentonite has a high content of titanium and iron-rich accessory minerals, such as anatase, magnetite, hematite and goethite. Other accessory minerals of significance are feldspars and quartz, whereas the content of sulphur

  8. Formation of accessory mineral bed layers during erosion of bentonite buffer material

    International Nuclear Information System (INIS)

    Schatz, Timothy; Kanerva, Noora

    2012-01-01

    Document available in extended abstract form only. dilute groundwater at a transmissive fracture interface, accessory phases within bentonite, such as quartz, feldspar, etc., might remain behind and form a filter bed or cake. As more and more montmorillonite is lost, the thickness of the accessory mineral bed increases and the continued transport of montmorillonite slows and possibly stops if the porosity of the filter bed is sufficiently compressed. Alternatively or concurrently, as the accessory mineral filter bed retains montmorillonite colloids, a filter cake composed of montmorillonite itself may be formed. Ultimately, depending on their extent, properties, and durability, such processes may provide the bentonite buffer system with an inherent, self-filtration mechanism which serves to limit the effects of colloidal erosion. A conceptual view of bentonite buffer extrusion and erosion in an intersecting fracture with formation of an accessory mineral filter bed and montmorillonite filter cake is presented in Figure 1. Due to the swelling pressure of the bentonite buffer, the situation described in Figure 1 may be analogous to that of the case of pressure filtration where a filter cake is formed by pressing a suspension through a filter medium and, by a mechanism known as expression, the filter cake is compressed by direct contact with a solid surface resulting in a reduction of its porosity. In order to examine whether the erosion of bentonite material through contact with dilute groundwater at a transmissive fracture interface could intrinsically result in 1) the formation of an accessory mineral filter bed and cake and/or 2) filter caking of montmorillonite itself, a series of laboratory tests were performed in a flow-through, horizontal, 1 mm aperture, artificial fracture system. Bentonite buffer material was simulated by using mixtures (75/25 weight percent ratio) of purified sodium montmorillonite and various additives serving as accessory mineral proxies

  9. SORPTION AND DISPERSION OF STRONTIUM RADIONUCLIDE IN THE BENTONITE-QUARTZ-CLAY AS BACKFILL MATERIAL CANDIDATE ON RADIOACTIVE WASTE REPOSITORY

    Directory of Open Access Journals (Sweden)

    Herry Poernomo

    2010-12-01

    Full Text Available The experiment of sorption and dispersion characteristics of strontium in the mixture of bentonite-quartz, clay-quartz, bentonite-clay-quartz as candidate of raw material for backfill material in the radioactive waste repository has been performed. The objective of this research is to know the grain size effect of bentonite, clay, and quartz on the weight percent ratio of bentonite to quartz, clay to quartz, bentonite to clay to-quartz can be gives physical characteristics of best such as bulk density (rb, effective porosity (e, permeability (K, best sorption characteristic such as distribution coefficient (Kd, and best dispersion characteristics such as dispersivity (a and effective dispersion coefficient (De of strontium in the backfill material candidate. The experiment was carried out in the column filled by the mixture of bentonite-quartz, clay-quartz, bentonite-clay-quartz with the weight percent ratio of bentonite to quartz, clay to quartz, bentonite to clay to quartz of 100/0, 80/20, 60/40, 40/60, 20/80, 0/100 respectively at saturated condition of water, then flowed 0.1 N Sr(NO32 as buffer solution with tracer of 0.05 Ci/cm3 90Sr as strontium radionuclide simulation was leached from immobilized radioactive waste in the radioactive waste repository. The concentration of 90Sr in the effluents represented as Ct were analyzed by Ortec b counter every 30 min, then by using profile concentration of Co and Ct, values of Kd, a and De of 90Sr in the backfill material was determined. The experiment data showed that the best results were -80+120 mesh grain size of bentonite, clay, quartz respectively on the weight percent ratio of bentonite to clay to quartz of 70/10/20 with physical characteristics of rb = 0.658 g/cm3, e = 0.666 cm3/cm3, and K = 1.680x10-2 cm/sec, sorption characteristic of Kd = 46.108 cm3/g, dispersion characteristics of a = 5.443 cm, and De = 1.808x10-03 cm2/sec can be proposed as candidate of raw material of backfill material

  10. Dynamics of crater formations in immersed granular materials

    Science.gov (United States)

    Varas, G.; Vidal, V.; Géminard, J.

    2009-12-01

    Craters are part of the widespread phenomena observed in nature. Among the main applications to natural phenomena, aside from meteorite impact craters, are the formation and growth of volcanic edifices, by successive ejecta emplacement and/or erosion. The time evolution and dynamics play a crucial role here, as the competition between volcanic-jet mass-flux (degassing and ejecta) and crater-size evolution may control directly the eruptive regime. Crater morphology in dry granular material has been extensively studied, both experimentally and theoretically. Most of these studies investigate the final, steady crater shape resulting from the collision of solid bodies with the material surface and scaling laws are derived. In immersed granular material, craters generated by an underwater vortex ring, or underwater impact craters generated by landslide, have been reported. In a previous experimental study, Gostiaux et al. [Gran. Matt., 2002] have investigated the dynamics of air flowing through an immersed granular layer. They reported that, depending on the flow rate, the system exhibits two qualitatively different regimes: At small flow rate, the bubbling regime during which bubbles escape the granular layer independently one from another; At large flow rate, the open-channel regime which corresponds to the formation of a channel crossing the whole thickness of the granular bed through which air escapes almost continuously. At intermediate flow rate, a spontaneous alternation between these two regimes is observed. Here, we report the dynamics of crater formations at the free surface of an immersed granular bed, locally crossed by an ascending gas flow. We reproduce the experimental conditions of Gostiaux et al. (2002) in two dimensions: In a vertical Hele-Shaw cell, the crater consists of two sand piles which develop around the location of the gas emission. We observe that the typical size of the crater increases logarithmically with time, independently of the gas

  11. Hydrothermal behaviors and long-term stability of bentonitic buffer material

    International Nuclear Information System (INIS)

    Lee, Jae Owan; Cho, Won Jin

    2007-01-01

    In hydrothermal reaction tests, smectite-to-illite conversion was identified using a domestic bentonite which is favorably considered as a buffer material, and its dependency on various hydrothermal conditions was investigated. The analysis results of the XRD and Si concentration indicated that the smectite-to- illite conversion was a major process of bentonite alteration under the hydrothermal conditions. The temperature, potassium concentration in solution, and pH were observed to significantly affect the smectite-to illite conversion. A model of conversion reaction rate was suggested evaluate the long-term stability of smectite composing a major constituent of bentonitic buffer. It was expected from the evaluation results that the smectite would keep its integrity for very long disposal time under a normal condition, while as it might be converted to illite by 50 percent after over 5 x 10 4 year of disposal time under a conservative condition and consequently lose its swelling capacity as a buffer material of a repository

  12. Breakage mechanics for granular materials in surface-reactive environments

    Science.gov (United States)

    Zhang, Yida; Buscarnera, Giuseppe

    2018-03-01

    It is known that the crushing behaviour of granular materials is sensitive to the state of the fluids occupying the pore space. Here, a thermomechanical theory is developed to link such macroscopic observations with the physico-chemical processes operating at the microcracks of individual grains. The theory relies on the hypothesis that subcritical fracture propagation at intra-particle scale is the controlling mechanism for the rate-dependent, water-sensitive compression of granular specimens. First, the fracture of uniaxially compressed particles in surface-reactive environments is studied in light of irreversible thermodynamics. Such analysis recovers the Gibbs adsorption isotherm as a central component linking the reduction of the fracture toughness of a solid to the increase of vapour concentration. The same methodology is then extended to assemblies immersed in wet air, for which solid-fluid interfaces have been treated as a separate phase. It is shown that this choice brings the solid surface energy into the dissipation equations of the granular matrix, thus providing a pathway to (i) integrate the Gibbs isotherm with the continuum description of particle assemblies and (ii) reproduce the reduction of their yield strength in presence of high relative humidity. The rate-effects involved in the propagation of cracks and the evolution of breakage have been recovered by considering non-homogenous dissipation potentials associated with the creation of surface area at both scales. It is shown that the proposed model captures satisfactorily the compression response of different types of granular materials subjected to varying relative humidity. This result was achieved simply by using parameters based on the actual adsorption characteristics of the constituting minerals. The theory therefore provides a physically sound and thermodynamically consistent framework to study the behaviour of granular solids in surface-reactive environments.

  13. An assessment of strontium sorption onto bentonite buffer material in waste repository.

    Science.gov (United States)

    Pathak, Pankaj

    2017-03-01

    In the present study, changes occurring in sorption characteristics of a representative bentonite (WIn-BT) exposed to SrCl 2 (0.001-0.1 M) under the pH range of 1-13 were investigated. Such interaction revealed a significant variation in surface charge density and binding energy of ions with respect to bentonite, and alteration in their physicochemical properties viz., specific surface area, cation exchange capacity, thermal and mechanical behaviour were observed. The distribution coefficients (k d ) calculated for sorption onto virgin (UCBT) and contaminated bentonite (CBT) indicated a greater influence of mineralogical changes occurred with variance of pH and strontium concentration. Notably, the sorption mechanism clearly elucidates the effect of structural negative charge and existence of anionic metal species onto CBT, and depicted the reason behind significant k d values at highly acidic and alkaline pH. The maximum k d of UCBT and CBT (0.001M SrCl2) were 8.99 and 2.92 L/kg, respectively, at the soil pH 8.5; whereas it was 2.37 and 1.23 L/kg at pH 1 for the CBT (0.1M SrCl2) and CBT (0.01M SrCl2) , respectively. The findings of this study can be useful to identify the physicochemical parameters of candidate buffer material and sorption reversibility in waste repository.

  14. The nature of quasistatic deformation in granular materials

    OpenAIRE

    ROUX, JN

    2005-01-01

    Strain in granular materials in quasistatic conditions under varying stress originate in (I) contact deformation and (II) rearrangements of the contact network. Depending on sample history and applied load, eiter mechanism might dominate. One may thus define rheological regimes I and II accordingly. Their porperties are presented and illustrated here with discrete numerical simulatiion results in 2 and 3 dimensions. This discussion of the microscopic physical origin of strain is shown to clar...

  15. Sealing performance assessments of bentonite and bentonite/crushed rock plugs

    International Nuclear Information System (INIS)

    Ouyang, Shoung.

    1990-01-01

    Bentonite and mixtures of bentonite and crushed rock are potential sealing materials for high level nuclear waste repositories. The materials have been used to form cap layers to reduce infiltration for mined waste tailings and can also be used to construct clay liners for municipal as well as industrial waste managements. American Colloid C/S granular dentonite and Apache Leap tuff have been mixed to prepare samples for laboratory flow testing. Bentonite weight percent and crushed tuff gradation are the major variables studied. The sealing performance assessments include high injection pressure flow tests, polyaxial flow tests, high temperature flow tests, and piping tests. The results indicate that an appropriate composition would have at least 25% bentonite by weight mixed with well-graded crushed rock. Hydraulic properties of the mixture plugs may be highly anisotropic if significant particle segregation occurs during sample installation and compaction. Temperature has no negative effects on the sealing performance within the test range from room temperature to 60C. The piping damage to the sealing performance is small if the maximum hydraulic gradient does not exceed 120 and 280 for 25 and 35% bentonite content, respectively. The hydraulic gradients above which flow of bentonite may take place are deemed critical. Analytical work includes the introduction of bentonite occupancy percentage and water content at saturation as two major parameters for the plug design. A permeability model developed is useful for the prediction of permeability in clays. A piping model permits the estimation of critical hydraulic gradient allowed before the flow of bentonite takes place. It can also be used to define the maximum allowable pore diameter of a protective filter layer

  16. Compaction dynamics of crunchy granular material

    Directory of Open Access Journals (Sweden)

    Guillard François

    2017-01-01

    Full Text Available Compaction of brittle porous material leads to a wide variety of densification patterns. Static compaction bands occurs naturally in rocks or bones, and have important consequences in industry for the manufacturing of powder tablets or metallic foams for example. Recently, oscillatory compaction bands have been observed in brittle porous media like snow or cereals. We will discuss the great variety of densification patterns arising during the compaction of puffed rice, including erratic compaction at low velocity, one or several travelling compaction bands at medium velocity and homogeneous compaction at larger velocity. The conditions of existence of each pattern are studied thanks to a numerical spring lattice model undergoing breakage and is mapped to the phase diagram of the patterns based on dimensionless characteristic quantities. This also allows to rationalise the evolution of the compaction behaviour during a single test. Finally, the localisation of compaction bands is linked to the strain rate sensitivity of the material.

  17. Compaction dynamics of crunchy granular material

    Science.gov (United States)

    Guillard, François; Golshan, Pouya; Shen, Luming; Valdès, Julio R.; Einav, Itai

    2017-06-01

    Compaction of brittle porous material leads to a wide variety of densification patterns. Static compaction bands occurs naturally in rocks or bones, and have important consequences in industry for the manufacturing of powder tablets or metallic foams for example. Recently, oscillatory compaction bands have been observed in brittle porous media like snow or cereals. We will discuss the great variety of densification patterns arising during the compaction of puffed rice, including erratic compaction at low velocity, one or several travelling compaction bands at medium velocity and homogeneous compaction at larger velocity. The conditions of existence of each pattern are studied thanks to a numerical spring lattice model undergoing breakage and is mapped to the phase diagram of the patterns based on dimensionless characteristic quantities. This also allows to rationalise the evolution of the compaction behaviour during a single test. Finally, the localisation of compaction bands is linked to the strain rate sensitivity of the material.

  18. Analysis of Cylindrical Granular Material Silos under Seismic Excitation

    Directory of Open Access Journals (Sweden)

    Christoph Butenweg

    2017-07-01

    Full Text Available Silos generally work as storage structures between supply and demand for various goods, and their structural safety has long been of interest to the civil engineering profession. This is especially true for dynamically loaded silos, e.g., in case of seismic excitation. Particularly thin-walled cylindrical silos are highly vulnerable to seismic induced pressures, which can cause critical buckling phenomena of the silo shell. The analysis of silos can be carried out in two different ways. In the first, the seismic loading is modeled through statically equivalent loads acting on the shell. Alternatively, a time history analysis might be carried out, in which nonlinear phenomena due to the filling as well as the interaction between the shell and the granular material are taken into account. The paper presents a comparison of these approaches. The model used for the nonlinear time history analysis considers the granular material by means of the intergranular strain approach for hypoplasticity theory. The interaction effects between the granular material and the shell is represented by contact elements. Additionally, soil–structure interaction effects are taken into account.

  19. Granular flow

    DEFF Research Database (Denmark)

    Mitarai, Namiko; Nakanishi, Hiizu

    2012-01-01

    Granular material is a collection of macroscopic particles that are visible with naked eyes. The non-equilibrium nature of the granular materials makes their rheology quite different from that of molecular systems. In this minireview, we present the unique features of granular materials focusing...... on the shear flow of dry granular materials and granule-liquid mixture....

  20. Characterisation of bentonites from Kutch, India and Milos, Greece - some candidate tunnel back-fill materials?

    Energy Technology Data Exchange (ETDEWEB)

    Olsson, Siv; Karnland, Ola (Clay Technology AB, Lund (Sweden))

    2009-12-15

    During the past decades comprehensive investigations have been made on bentonite clays in order to find optimal components of the multi-barrier system of repositories for radioactive waste. The present study gives a mineralogical characterisation of some selected bentonites, in order to supply some of the necessary background data on the bentonites for evaluating their potential as tunnel back-fill materials. Two bentonites from the island of Milos, Greece (Milos BF 04 and BF 08), and two bentonites from Kutch, India (Kutch BF 04 and BF 08) were analysed for their grain size distribution, cation exchange properties and chemical composition. The mineralogical composition was determined by X-ray diffraction analysis and evaluated quantitatively by use of the Siroquant software. Both the bulk bentonite and the <1mum fraction were analyzed when relevant. Prior to the chemical analyses the <1 mum fractions were converted to homo-ionic clays and purified by dialysis. The chemical data were used for calculating the structural formula of the smectites. Milos BF 04 contains ca. 10% particles >63 mum. The bentonite is distinguished by a high content of dolomite and calcite, which make up almost 25% of the bulk sample. The major accessory minerals are K-feldspars and plagioclase, whereas the content of sulphur-bearing minerals is very low (0.06% total S). Smectite makes up around 60% of the bulk sample, which has a CEC value of 73 meq/100 g. The pool of interlayer cations has a composition Mg>Ca>>Na>>K. The X-ray diffraction characteristics and the high potassium content (1.03% K{sub 2}O) of the <1 mum fraction suggest that the smectite is interstratified with ca. 10% illitic layers. Based on the charge distribution the smectite should be classified as montmorillonite and according to the structural formula, Mg predominates over Fe in the octahedral sheet. However, remnants of Mg-carbonates, if present, may be a source of error in the formula calculation. Milos BF 08 has a

  1. Porewater salinity and the development of swelling pressure in bentonite-based buffer and backfill materials

    Energy Technology Data Exchange (ETDEWEB)

    Dixon, D.A. [Atomic Energy of Canada Limited (Canada)

    2000-06-01

    At the depths proposed for a nuclear fuel waste repository, it is likely that saline groundwater conditions will be encountered in the granitic rocks of Finland and Canada. The potential for saline groundwater to influence of the ability of bentonite-based buffer and backfilling materials to swell and thereby generate swelling pressure has been reviewed. Based on the data collected from existing literature, it would appear that porewater salinities as high as 100 g/l will not compromise the ability of confined, bentonite-based materials to develop a swelling pressure of at least 100 kPa on its confinement, provided the effective clay dry density (ECDD), exceeds approximately 0.9 Mg/m{sup 3}. At densities less than approximately 0.9 Mg/m{sup 3} the swelling pressure of bentonite-based materials may be reduced and become sensitive to salt concentration. The influence of porewater salinity on swelling pressure can be compared on the basis of the ECDD required to develop 100 kPa of swelling pressure. In order to generate 100 kPa of swelling pressure an ECDD of approximately 0.7 Mg/m{sup 3} is required to be present under fresh water or brackish porewater conditions. This density would need to be increased to approximately 0.9 Mg/m{sup 3} where the groundwater conditions were saline. The impact that groundwater salinity will have on density specifications for buffer and backfilling materials are discussed with reference to the nuclear fuel waste disposal concepts of Finland and Canada. (orig.)

  2. Variety and variability of bentonites as buffer materials in radioactive waste disposal

    International Nuclear Information System (INIS)

    Sato, Tsutomu

    1994-01-01

    Bentonite which is considered to be most promising as the buffer material in the formation disposal of high level radioactive waste is the clay having Montmorillonite of smectite group as the main component mineral. The clay of smectite group shows different properties, and its range of variability is wide. In this report, the clay minerals of smectite group and their variety are explained from the viewpoint of crystal chemistry, and the difference in expansion property, water recovery property and long period stability, which are expected for the buffer material in formation disposal, in various smectite clays is described. The trend of the investigation of the buffer materials and the importance of making their standard are referred to. In the formation disposal of high level radioactive waste, multiple barrier concept is investigated. The expectation for the development of intelligent materials is large. Bentonite established the position as one of the intelligent materials. The factors controlling the properties of clay are the compositions of clay minerals, nonclay minerals, organic substances, exchangeable cations and soluble salts and texture. (K.I.)

  3. {sup 137}Cs sorption into bentonite from Cidadap-Tasikmalaya as buffer material for disposal demonstration plant facility at Serpong

    Energy Technology Data Exchange (ETDEWEB)

    Setiawan, B., E-mail: bravo@batan.go.id; Sriwahyuni, H., E-mail: bravo@batan.go.id; Ekaningrum, NE., E-mail: bravo@batan.go.id; Sumantry, T., E-mail: bravo@batan.go.id [Radwaste Technology Center-National Nuclear Energy Agency, PUSPIPTEK, Serpong-Tangerang 15310 (Indonesia)

    2014-03-24

    According to co-location principle, near surface disposal type the disposal demonstration plant facility will be build at Serpong nuclear area. The facility also for anticipation of future needs to provide national facility for the servicing of radwaste management of non-nuclear power plant activity in Serpong Nuclear Area. It is needs to study the material of buffer and backfill for the safety of demonstration plant facility. A local bentonite rock from Cidadap-Tasikmalaya was used as the buffer materials. Objective of experiment is to find out the specific data of sorption characteristic of Cidadap bentonite as buffer material in a radwaste disposal system. Experiments were performed in batch method, where bentonite samples were contacted with CsCl solution labeled with Cs-137 in 100 ml/g liquid:solid ratio. Initial Cs concentration was 10{sup −8} M and to study the effects of ionic strength and Cs concentration in solution, 0.1 and 1.0 M NaCl also CsCl concentration ranging 10{sup −8} - 10{sup −4} M were added in solution. As the indicator of Cs saturated in bentonite samples, Kd value was applied. Affected parameters in the experiment were contact time, effects of ionic strength and concentration of CsCl. Results showed that sorption of Cs by bentonite reached constantly after 16 days contacted, and Kd value was 10.600 ml/g. Effect of CsCl concentration on Kd value may decreased in increased in CsCl concentration. Effect of ionic strength increased according to increased in concentration of background and would effect to Kd value due to competition of Na ions and Cs in solution interacts with bentonite. By obtaining the bentonite character data as buffer material, the results could be used as the basis for making of design and the basic of performance assessment the near surface disposal facility in terms of isolation capacity of radwaste later.

  4. Influence of material and solution composition on the extrusion/erosion behaviour of compacted bentonite

    International Nuclear Information System (INIS)

    Schatz, Timothy; Martikainen, Jari; Koskinen, Kari

    2010-01-01

    Document available in extended abstract form only. In principle, in a KBS-3 type repository, the volume of a deposition hole is fixed and the bentonite buffer mass accordingly balanced to lead to the development of a suitable swelling pressure upon saturation. However, fractures intersecting the deposition holes give rise to the possibility that volume constrained conditions do not universally exist. Such fractures may provide pathways for the continued, localised, free swelling of bentonite buffer material. Loss of mass from the deposition hole by extrusion into intersecting fractures may compromise the long-term safety and performance of the buffer component of the engineered barrier system. Furthermore, the continued hydration and expansion of extruded bentonite in these fracture environments could lead to the separation of colloid-sized (or larger) particles by diffusion or shear which may have to be accounted for in possible radionuclide migration scenarios. Geochemical conditions, with respect to both solution and material composition, are considered to play important roles regarding the fracture extrusion/erosion of bentonite buffer material. For example, calcium-montmorillonite exhibits limited free swelling relative to sodium-montmorillonite and the colloidal and rheological properties of montmorillonite dispersions are sensitive to the presence of electrolytes. Insofar as both the buffer material composition (due to ion exchange) and groundwater composition (dilution resulting from infiltration of glacial melt water) are expected to evolve with time, so too might the potential for fracture extrusion/erosion of buffer material vary over time. The hydraulic characteristics of the intersecting fracture are expected to influence the extrusion/erosion process as well. To evaluate the effect of material and solution composition on the potential for extrusion of buffer mass into intersecting fractures, a series of batch experiments were performed. In these

  5. Leaching models for multiple immersed materials and for granular materials flushed in a column

    NARCIS (Netherlands)

    Brouwers, H.J.H.

    1997-01-01

    The present paper addresses the leaching of hazardous contaminants from immersed and replenished materials and from granular materials flushed in a column. First, the leaching of an immersed material in contact with a limited volume of leachant is studied. The mass transfer from material to leachant

  6. Thermal conductivity tests on buffermasses of bentonite/silt

    International Nuclear Information System (INIS)

    Knutsson, S.

    1977-09-01

    The investigation concerns the thermal conductivity of the bentonite/quartz buffer mass suggested as embedding substance for radioactive canisters. The first part presents the theoretical relationships associated with the various heat transfer mechanisms in moist granular materials. Chapter 3 describes the author's experimental determination of the thermal conductivity of the buffer mass. The tested mass consisted of 10 percent (by weight) bentonite and 90 percent natural silt. Four tests were made with different water content values and degree of water saturation. A comparison between the measured and calculated thermal conductivities is given. It is shown that the conductivity can be calculated with an accuracy of +-20 percent. (author)

  7. Implicit integration of plasticity models for granular materials

    DEFF Research Database (Denmark)

    Ahadi, A.; Krenk, Steen

    2003-01-01

    A stress integration algorithm for granular materials based on fully implicit integration with explicit updating is presented. In the implicit method the solution makes use of the gradient to the potential surface at the final stress state which is unknown. The final stress and hardening parameters...... stresses are not supported the functions and their derivatives are not representative outside the compressive octant of the principal stress space. The elastic predictor is therefore preconditioned in order to ensure that the first predictor is within the valid region. Capability and robustness...

  8. A formula for determination of swelling characteristics of buffer material containing bentonite and evaluation of self-sealing performance

    International Nuclear Information System (INIS)

    Komine, Hideo; Ogata, Nobuhide

    1998-01-01

    High level radioactive waste disposal facility is planned to construct in a rock board deeper than some hundreds meter at underground, it is necessary to develop a material to refill the gap between waste container and its circumferential rock board. For this material it is required to have high water sealing and swellability, and bentonite is expected to use such application. Production of soil buffer materials containing bentonite is difficult to obtain required dry density by solidifying due to in situ roll-pressing, so it is, at present, thought to be an effective method to carry a block produced in a factory to a pit for disposal to settle. When supposing to produce and settle such buffer material, a gap forming between the buffer material and circumferential rock board or waste container has a large possibility to make a water path when remaining without treating it. Therefore, the buffer material is required to have a function to fill gap portion by swelling deformation and to proof water. In this study, in order to evaluated self-sealing of bentonite, due to a theoretical examination and a laboratory experiment on swelling behavior of soil materials containing bentonite, a swelling evaluation equation of the buffer materials was proposed. And, an application example for outlined design of an actual high level radioactive waste disposal facility was introduced. (G.K.)

  9. Relating water and air flow characteristics in coarse granular materials

    DEFF Research Database (Denmark)

    Andreasen, Rune Røjgaard; Canga, Eriona; Poulsen, Tjalfe Gorm

    2013-01-01

    Water pressure drop as a function of velocity controls w 1 ater cleaning biofilter operation 2 cost. At present this relationship in biofilter materials must be determined experimentally as no 3 universal link between pressure drop, velocity and filter material properties have been established. 4...... Pressure drop - velocity in porous media is much simpler and faster to measure for air than for water. 5 For soils and similar materials, observations show a strong connection between pressure drop – 6 velocity relations for air and water, indicating that water pressure drop – velocity may be estimated 7...... from air flow data. The objective of this study was, therefore, to investigate if this approach is valid 8 also for coarse granular biofilter media which usually consists of much larger particles than soils. In 9 this paper the connection between the pressure drop – velocity relationships for air...

  10. Extrusion and erosion of bentonite buffer material in a flow-through, horizontal, artificial fracture system

    International Nuclear Information System (INIS)

    Schatz, Timothy; Kanerva, Noora; Martikainen, Jari

    2012-01-01

    Document available in extended abstract form only. One scenario of interest for the long-term safety assessment of a spent nuclear fuel repository involves the loss of bentonite buffer material through contact with dilute groundwater at a transmissive fracture interface [SKB 2011, Posiva 2012]. In order to simulate the potential extrusion/erosion behaviour of bentonite buffer material in such an environment, a series of small-scale, flow-through, artificial fracture experiments were performed in which swelling clay material could extrude/erode into a well defined, system (see Figure 1). The fracture dimensions were 24 cm (length) x 24 cm (width) x 1 mm (aperture) and the compacted sample dimensions were 2 cm (height) x 2 cm (diameter). Extrusion/erosion effects were analysed against solution chemistry (salt concentration and composition), material composition (sodium montmorillonite and admixtures with calcium montmorillonite), and flow velocity. No erosion was observed for sodium montmorillonite against solution compositions from 10 to 0.5 g/L NaCl. Comparatively, most reports in the literature indicate that a concentration of 0.5 g/L NaCl (8.6 mM) is below, in some cases well below, the (experimentally observed) critical coagulation concentration (CCC) for the colloidal sodium montmorillonite/sodium chloride system [Garcia-Garcia et al. 2007]. It was also the case that no erosion was observed for 50/50 calcium/sodium montmorillonite against 0.5 g/L NaCl. Overall, the results of the flow-through, artificial fracture tests, indicate stability to erosion down to a dilute concentration range between 8 to 4 mM NaCl for both sodium and 50/50 calcium/sodium montmorillonite. These limits compare favorably to the erosion stability limits observed by Birgersson et al. [2009] in the case of the latter material but less so for the former. A number of tests were conducted for which measurable erosion was observed. The calculated mass loss rates for these tests, expressed in

  11. Temperature scaling in a dense vibrofluidized granular material.

    Science.gov (United States)

    Sunthar, P; Kumaran, V

    1999-08-01

    The leading order "temperature" of a dense two-dimensional granular material fluidized by external vibrations is determined. The grain interactions are characterized by inelastic collisions, but the coefficient of restitution is considered to be close to 1, so that the dissipation of energy during a collision is small compared to the average energy of a particle. An asymptotic solution is obtained where the particles are considered to be elastic in the leading approximation. The velocity distribution is a Maxwell-Boltzmann distribution in the leading approximation. The density profile is determined by solving the momentum balance equation in the vertical direction, where the relation between the pressure and density is provided by the virial equation of state. The temperature is determined by relating the source of energy due to the vibrating surface and the energy dissipation due to inelastic collisions. The predictions of the present analysis show good agreement with simulation results at higher densities where theories for a dilute vibrated granular material, with the pressure-density relation provided by the ideal gas law, are in error.

  12. Thermal conductivity of compacted bentonite as a buffer material for a high-level radioactive waste repository

    International Nuclear Information System (INIS)

    Lee, Jae Owan; Choi, Heuijoo; Lee, Jong Youl

    2016-01-01

    Highlights: • The thermal conductivities were measured under various disposal conditions. • They were significantly influenced by the water content and dry density. • They were not sensitive to the temperature and the anisotropic structure. • A new model of thermal conductivity was proposed for the thermal analysis. - Abstract: Bentonite buffer is one of the major barrier components of a high-level radioactive waste (HLW) repository, and the thermal conductivity of the bentonite buffer is a key parameter for the thermal performance assessment of the HLW repository. This study measured the thermal conductivity of compacted bentonite as a buffer material and investigated its dependence upon various disposal conditions: the dry density, water content, anisotropic structure of the compacted bentonite, and temperature. The measurement results showed that the thermal conductivity was significantly influenced by the water content and dry density of the compacted bentonite, while there was not a significant variation with respect to the temperature. The anisotropy of the thermal conductivity had a negligible variation for an increasing dry density. The present study also proposed a geometric mean model of thermal conductivity which best fits the experimental data.

  13. Failure evolution in granular material retained by rigid wall in active mode

    Science.gov (United States)

    Pietrzak, Magdalena; Leśniewska, Danuta

    2012-10-01

    This paper presents a detailed study of a selected small scale model test, performed on a sample of surrogate granular material, retained by a rigid wall (typical geotechnical problem of earth thrust on a retaining wall). The experimental data presented in this paper show that the deformation of granular sample behind retaining wall can undergo some cyclic changes. The nature of these cycles is not clear - it is probably related to some micromechanical features of granular materials, which are recently extensively studied in many research centers in the world. Employing very precise DIC (PIV) method can help to relate micro and macro-scale behavior of granular materials.

  14. Micromechanical definition of an entropy for quasi-static deformation of granular materials

    NARCIS (Netherlands)

    Rothenburg, L.; Kruyt, Nicolaas P.

    2009-01-01

    A micromechanical theory is formulated for quasi-static deformation of granular materials, which is based on information theory. A reasoning is presented that leads to the definition of an information entropy that is appropriate for quasi-static deformation of granular materials. This definition is

  15. Hydro-mechanical behaviour of bentonite-based materials used for high-level radioactive waste disposal

    International Nuclear Information System (INIS)

    Wang, Q.

    2012-01-01

    This study deals with the hydro-mechanical behaviour of compacted bentonite-based materials used as sealing materials in high-level radioactive waste repositories. The pure MX80 bentonite, mixtures of MX80/crushed clay-stone and MX80/sand were used in the investigation. An experimental study on the swelling pressure of the bentonite-based materials was first performed. The results evidenced the effects of water chemistry, hydration procedure and duration, pre-existing technological void and experimental methods. Emphasis was put on the relationship between the swelling pressure and the final dry density of bentonite. Afterwards, the water retention test, hydration test and suction controlled oedometer test were conducted on samples with different voids including the technological void and the void inside the soil. By introducing the parameters as bentonite void ratio and water volume ratio, an overall analysis of the effects of voids on the hydro-mechanical response of the compacted material was performed. To get better insight into the seal evolution in case of technological void, the effects of final dry density and hydration time on the microstructure features were also characterized. Then, the hydraulic properties under unsaturated state were investigated by carrying out water retention test and infiltration test as well as the microstructure observation. The results obtained allowed relating the variation of hydraulic conductivity to the microstructure changes. A small scale (1/10) mock up test of the SEALEX in situ experiment was also performed to study the recovery capacity of bentonite-based material with consideration of a technological void. The results were used for interpreting the in-situ observations. With a reduced time scale, it provides useful information for estimating the saturation duration and sealing effectiveness of the field design. Finally, the experimental data obtained in the laboratory on bentonite/sand mixture were interpreted in the

  16. Experimental study of shear bands formation in a granular material

    Directory of Open Access Journals (Sweden)

    Nguyen Thai Binh

    2017-01-01

    Full Text Available We present an experimental investigation of the formation of shear bands in a granular sample submitted to a biaxial test. Our principal result is the direct observation of the bifurcation at the origin of the localization process in the material. At the bifurcation, the shear band is spatially extended: we observe a breaking of symmetry without any sudden localization of the deformation in a narrow band. Our work thus allows to clearly distinguish different phenomena: bifurcation which is a ponctual event which occurs before the peak, localization which is a process that covers a range of deformation of several percents during which the peak occurs and finally stationary shear bands which are well-defined permanent structures that can be observed at the end of the localization process, after the peak.

  17. Fundamental properties of monolithic bentonite buffer material formed by cold isostatic pressing for high-level radioactive waste repository

    International Nuclear Information System (INIS)

    Kawakami, S.; Yamanaka, Y.; Kato, K.; Asano, H.; Ueda, H.

    1999-01-01

    The methods of fabrication, handling, and emplacement of engineered barriers used in a deep geological repository for high level radioactive waste should be planned as simply as possible from the engineering and economic viewpoints. Therefore, a new concept of a monolithic buffer material around a waste package have been proposed instead of the conventional concept with the use of small blocks, which would decrease the cost for buffer material. The monolithic buffer material is composed of two parts of highly compacted bentonite, a cup type body and a cover. As the forming method of the monolithic buffer material, compaction by the cold isostatic pressing process (CIP) has been employed. In this study, monolithic bentonite bodies with the diameter of about 333 mm and the height of about 455 mm (corresponding to the approx. 1/5 scale for the Japanese reference concept) were made by the CIP of bentonite powder. The dry densities: ρd of the bodies as a whole were measured and the small samples were cut from several locations to investigate the density distribution. The swelling pressure and hydraulic conductivity as function of the monolithic body density for CIP-formed specimens were also measured. High density (ρd: 1.4--2.0 Mg/m 3 ) and homogeneous monolithic bodies were formed by the CIP. The measured results of the swelling pressure (3--15 MPa) and hydraulic conductivity (0.5--1.4 x 10 -13 m/s) of the specimens were almost the same as those for the uniaxial compacted bentonite in the literature. It is shown that the vacuum hoist system is an applicable handling method for emplacement of the monolithic bentonite

  18. Electrochemical and radiochemical material transport examinations in humate-containing montmorillonite a bentonite thin layers

    International Nuclear Information System (INIS)

    Antal, K.; Joo, P.

    1999-01-01

    Various humate-containing H-bentonite layers were investigated using 137 Cs ion transport and radio absorption measuring method. These processes can model radioactive contamination migration in soils exposed to acid rains. Experiment using montmorillonite and bentonite layers are discussed, and the results obtained with electrochemical and radioisotope absorption techniques are presented. (R.P.)

  19. Thermodynamical aspects of modeling the mechanical response of granular materials

    International Nuclear Information System (INIS)

    Elata, D.

    1995-01-01

    In many applications in rock physics, the material is treated as a continuum. By supplementing the related conservation laws with constitutive equations such as stress-strain relations, a well-posed problem can be formulated and solved. The stress-strain relations may be based on a combination of experimental data and a phenomenological or micromechanical model. If the model is physically sound and its parameters have a physical meaning, it can serve to predict the stress response of the material to unmeasured deformations, predict the stress response of other materials, and perhaps predict other categories of the mechanical response such as failure, permeability, and conductivity. However, it is essential that the model be consistent with all conservation laws and consistent with the second law of thermodynamics. Specifically, some models of the mechanical response of granular materials proposed in literature, are based on intergranular contact force-displacement laws that violate the second law of thermodynamics by permitting energy generation at no cost. This diminishes the usefulness of these models as it invalidates their predictive capabilities. [This work was performed under the auspices of the U.S. DOE by Lawrence Livermore National Laboratory under Contract No. W-7405-ENG-48.

  20. BENTONITE PROCESSING

    Directory of Open Access Journals (Sweden)

    Anamarija Kutlić

    2012-07-01

    Full Text Available Bentonite has vide variety of uses. Special use of bentonite, where its absorbing properties are employed to provide water-tight sealing is for an underground repository in granites In this paper, bentonite processing and beneficiation are described.

  1. Sorption and desorption reactions of radionuclides with a crushed basalt-bentonite packing material

    International Nuclear Information System (INIS)

    Barney, G.S.; Lane, D.L.; Allen, C.C.; Jones, T.E.

    1985-04-01

    Current design of waste packages for disposal of high-level radioactive wastes in underground basalt formations includes a layer of packing material that surrounds the waste container. One of the functions of this material is to limit the release of radionuclides from a breached container into groundwater by providing a low hydraulic conductivity zone and by sorbing dissolved radionuclides. The objective of this study was to assess the radionuclide sorption capability of a proposed packing material composed of 25% sodium bentonite and 75% crushed basalt (by weight). Sorption and desorption reactions of several important waste radioelements (neptunium, uranium, plutonium, technetium, selenium, and radium) were investigated in the absence of air at 90 0 C. Uranium and neptunium were sorbed by slow reactions that follow first-order kinetics. The reaction rates are probably controlled by reduction of weakly sorbed uranium(VI) and neptunium(V) by ferrous iron in the crushed basalt component. Technetium(VII) was not reduced or sorbed under these conditions. Freundlich sorption and desorption isotherms for a given radionuclide were non-singular and show a strong tendency for sorption hysteresis. Applying the isotherm data to a one-dimensional transport model indicated that hysteretic sorption on the packing material provides an important safety factor in controlling releases of some radionuclides

  2. Analytical study on the suitability of using bentonite coated gravel as a landfill liner material

    International Nuclear Information System (INIS)

    Roberts, Anel A.; Shimaoka, Takayuki

    2008-01-01

    This study investigates the feasibility of using bentonite coated gravel (BCG) as a liner material for waste landfills. BCG has proven to be a very effective capping material/method for the remediation of contaminated sediments in aquatic environments. The concept of BCG is similar to that of peanuts/almonds covered with chocolate; each aggregate particle has been covered with the clayey material. Laboratory tests were aimed at evaluating regulated and non-regulated factors for liner materials, i.e., permeability and strength. Tests included X-ray diffraction, methylene blue absorption, compaction, free swelling, permeability, 1D consolidation, triaxial compression and cone penetration. The compactive efforts used for this study were the reduced Proctor, standard Proctor, intermediate Proctor, modified Proctor and super modified Proctor. The compactive energy corresponding to each effort, respectively, is as follows: 355.5, 592.3, 1196.3, 2693.3, and 5386.4 kJ/m 3 . Results revealed that even though aggregate content represents 70% of the weight of the material, hydraulic conductivities as low as 6 x 10 -10 cm/s can be achieved when proper compactive efforts are used. Compressibility is very low for this material even at low (or no) compactive efforts. Results also demonstrated how higher compactive efforts can lower the permeability of BCG; however, over-compaction creates fractures in the aggregate core of BCG that could increase permeability. Moreover, higher compactive efforts create higher swelling pressures that could compromise the performance of a barrier constructed using BCG. As a result of this study, moderate compactive efforts, i.e., intermediate Proctor or modified Proctor, are recommended for constructing a BCG barrier. Using moderate compactive efforts, very low hydraulic conductivities, good workability and good trafficability are easily attainable

  3. Shear test on viscoelastic granular material using Contact Dynamics simulations

    Science.gov (United States)

    Quezada, Juan Carlos; Sagnol, Loba; Chazallon, Cyrille

    2017-06-01

    By means of 3D contact dynamic simulations, the behavior of a viscoelastic granular material under shear loading is investigated. A viscoelastic fluid phase surrounding the solid particles is simulated by a contact model acting between them. This contact law was implemented in the LMGC90 software, based on the Burgers model. This model is able to simulate also the effect of creep relaxation. To validate the proposed contact model, several direct shear tests were performed, experimentally and numerically using the Leutner device. The numerical samples were created using spheres with two particle size distribution, each one identified for two layers from a road structure. Our results show a reasonable agreement between experimental and numerical data regarding the strain-stress evolution curves and the stress levels measured at failure. The proposed model can be used to simulate the mechanical behavior of multi-layer road structure and to study the influence of traffic on road deformation, cracking and particles pull-out induced by traffic loading.

  4. Effect of organic carbon content of the domestic bentonite on the performance of buffer material in a high-level waste repository

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Won Jin; Lee, Jae Owan; Kang, Chul Hyung [Korea Atomic Energy Research Institute, Taejon (Korea)

    1999-12-01

    The organic carbon content of the domestic bentonite have been measured, and its effects on the performance of buffer are analyzed. The total carbon content and the organic carbon content were in the range of 3160 to 3600 and 2400 to 2800 ppm, respectively. The aqueous phase equilibrium concentrations of total carbon and organic carbon in bentonite-water mixture were in the range of 25 to 50 ppm and 4 to 18 ppm, respectively. The results indicate that the effect of organic matter in the domestic bentonite on the performance of buffer material were insignificant. 33 refs., 15 figs., 10 tabs. (Author)

  5. Reinforced cassava starch based edible film incorporated with essential oil and sodium bentonite nanoclay as food packaging material.

    Science.gov (United States)

    Iamareerat, Butsadee; Singh, Manisha; Sadiq, Muhammad Bilal; Anal, Anil Kumar

    2018-05-01

    Biodegradable packaging in food materials is a green technology based novel approach to replace the synthetic and conventional packaging systems. This study is aimed to formulate the biodegradable cassava starch based films incorporated with cinnamon essential oil and sodium bentonite clay nanoparticles. The films were characterized for their application as a packaging material for meatballs. The cassava starch films incorporated with sodium bentonite and cinnamon oil showed significant antibacterial potential against all test bacteria; Escherichia coli , Salmonella typhimurium and Staphylococcus aureus. Antibacterial effect of films increased significantly when the concentration of cinnamon oil was increased. The cassava starch film incorporated with 0.75% (w/w) sodium bentonite, 2% (w/w) glycerol and 2.5% (w/w) cinnamon oil was selected based on physical, mechanical and antibacterial potential to evaluate shelf life of meatballs. The meatballs stored at ambient temperature in cassava starch film incorporated with cinnamon oil and nanoclay, significantly inhibited the microbial growth till 96 h below the FDA limits (10 6  CFU/g) in foods compared to control films that exceeded above the limit within 48 h. Hence cassava starch based film incorporated with essential oils and clay nanoparticles can be an alternate approach as a packaging material for food industries to prolong the shelf life of products.

  6. Study of the applicability of the diffusion model of bentonite buffer material (2)

    International Nuclear Information System (INIS)

    Matsumoto, Kazuhiro; Fujita, Tomoo

    2011-03-01

    Bentonite buffer material is envisaged as a component of the engineered barrier system for high-level radioactive waste disposal. As a result of its swelling property, the buffer may extrude into the surrounding host rock through open fractures. If this persists for extremely long periods of time, the buffer extrusion could lead to a reduction of buffer density, which may in turn degrade the expected performance. In this report, verification of the solid phase diffusion theory of the past was performed and future problems were extracted based on expertise. Results obtained from the studies are summarized as follows; 1) Verification of solid phase diffusion theory: Comparison with the solid phase diffusion coefficient based on an swelling experiment and the theoretical value was performed. As a result of simulation, the theoretical diffusion velocity had slower than the experimental one. 2) Simulation of an extrusion experiment: As a result of performing the simulation of an extrusion experiment using the fitting line based on an experiment, it was well in agreement in comparison. 3) Expert review: The expert propel an application of advection-diffusion equation to the extrusion model. It is necessary to attain optimization of a model, repeating the simulation of element experiment and those results and performing it based on the result of this experiment and a review. (author)

  7. Physicochemical, mineralogical and mechanical properties of domestic bentonite and bentonite-sand mixture as a buffer material in the high-level waste repository

    International Nuclear Information System (INIS)

    Cho, Won Jin; Lee, Jae Owan; Kang, Chul Hyung; Chun, Kwan Sik

    1999-09-01

    The physicochemical properties such as specific weight, free swell rate, chemical composition, cation exchange capacity (CEC), surface area and distribution coefficient of Kyunggju bentonite were measured, and the mineralogical analysis was performed to investigate the mineralogical composition. For the compacted bentonite and the mixture of bentonite and sand, the liquid and plastic limit, the linear shrinkage, and compaction property, the compression property, the shear property, and the consolidation property were investigated and analyzed. The bentonite contains montmorillonite (70 percent), feldspar (29 percent), and small amounts of quartz(-1 percent). The compressive strengths of bentonites are increased from 0.53 MPa to 8.83 MPa rapidly with increasing dry density of 1.4 g/cm 3 to 1.8 g/cm 3 . The cohesion and internal friction angles of bentonites with the dry density of 1.4 g/cm 3 to 1.8 g/cm 3 are in the range of 500 to 1100 kPa and 27 to 50 degree, respectively. (Author). 21 refs., 20 tabs., 46 figs

  8. Physicochemical, mineralogical and mechanical properties of domestic bentonite and bentonite-sand mixture as a buffer material in the high-level waste repository

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Won Jin; Lee, Jae Owan; Kang, Chul Hyung; Chun, Kwan Sik

    1999-09-01

    The physicochemical properties such as specific weight, free swell rate, chemical composition, cation exchange capacity (CEC), surface area and distribution coefficient of Kyunggju bentonite were measured, and the mineralogical analysis was performed to investigate the mineralogical composition. For the compacted bentonite and the mixture of bentonite and sand, the liquid and plastic limit, the linear shrinkage, and compaction property, the compression property, the shear property, and the consolidation property were investigated and analyzed. The bentonite contains montmorillonite (70 percent), feldspar (29 percent), and small amounts of quartz(-1 percent). The compressive strengths of bentonites are increased from 0.53 MPa to 8.83 MPa rapidly with increasing dry density of 1.4 g/cm{sup 3} to 1.8 g/cm{sup 3}. The cohesion and internal friction angles of bentonites with the dry density of 1.4 g/cm{sup 3} to 1.8 g/cm{sup 3} are in the range of 500 to 1100 kPa and 27 to 50 degree, respectively. (Author). 21 refs., 20 tabs., 46 figs.

  9. The influence of the fractal particle size distribution on the mobility of dry granular materials

    Directory of Open Access Journals (Sweden)

    Vallejo Luis E.

    2017-01-01

    Full Text Available This study presents an experimental analysis on the influence of the particle size distribution (psd on the mobility of dry granular materials. The psd obeys a power law of the form: N(L>d=kd-Df, where N is the number of particles with diameter L greater than a given diameter d, k is a proportionality constant, and Df is the fractal dimension of the psd. No laboratory or numerical study has been conducted to date analysing how a fractal psd influences the mobility of granular flows as in the case of rock avalanches. In this study, the flow characteristics of poly-dispersed granular materials that have a fractal psd were investigated in the laboratory. Granular mixtures having different fractal psd values were placed in a hollow cylinder. The cylinder was lifted and the distance of flow of the mixture was measured with respect to the original position of the cylinder. It was determined that the distance of flow of the mixtures was directly related to their fractal psd values. That is, the larger the distance of flow of the mixture, the larger is the fractal psd of the granular mixture tested. Thus, the fractal psd in dry granular mixtures seems to have a large influence on the easiness by which dry granular mixtures move in the field.

  10. Editorial: Modelling and computational challenges in granular materials

    NARCIS (Netherlands)

    Weinhart, Thomas; Thornton, Anthony Richard; Einav, Itai

    2015-01-01

    This is the editorial for the special issue on “Modelling and computational challenges in granular materials” in the journal on Computational Particle Mechanics (CPM). The issue aims to provide an opportunity for physicists, engineers, applied mathematicians and computational scientists to discuss

  11. "Coulombic Viscosity" In Granular Materials: Planetary and Astrophysical Implications

    Science.gov (United States)

    Marshall, J. R.

    1999-01-01

    The term "Coulombic viscosity" is introduced here to define an empirically observed phenomenon from experiments conducted in both microgravity, and in ground-based 1-g conditions. In the latter case, a sand attrition device was employed to test the longevity of aeolian materials by creating two intersecting grain-circulation paths or cells that would lead to most of the grain energy being expended on grain-to-grain collisions (simulating dune systems). In the areas in the device where gravitationally-driven grain-slurries recycled the sand, the slurries moved with a boundary-layer impeded motion down the chamber walls. Excessive electrostatic charging of the grains during these experiments was prevented by the use of an a.c. corona (created by a Tesla coil) through which the grains passed on every cycle. This created both positive and negative ions which neutralized the triboelectrically-generated grain charges. When the corona was switched on, the velocity of the wall-attached slurries increased by a factor of two as approximately determined by direct observation. What appeared to be a freely-flowing slurry of grains impeded only by intergranular mechanical friction, had obviously been significantly retarded in its motion by electrostatic forces between the grains; with the charging reduced, the grains were able to move past one another without a flow "viscosity" imposed by the Coulombic intergranular forces. A similar phenomenon was observed during microgravity experiments aboard Space Shuttle in USML-1 & USML-2 spacelabs where freely-suspended clouds of sand were being investigated for their potential to for-m aggregates. In this environment, the grains were also charged electrostatically (by natural processes prior to flight), but were free from the intervention of gravity in their interactions. The grains were dispersed into dense clouds by bursts of air turbulence and allowed to form aggregates as the ballistic and turbulent motions damped out. During this

  12. "Coulombic Viscosity" In Granular Materials: Planetary and Astrophysical Implications

    Science.gov (United States)

    Marshall, J. R.

    1999-09-01

    The term "Coulombic viscosity" is introduced here to define an empirically observed phenomenon from experiments conducted in both microgravity, and in ground-based 1-g conditions. In the latter case, a sand attrition device was employed to test the longevity of aeolian materials by creating two intersecting grain-circulation paths or cells that would lead to most of the grain energy being expended on grain-to-grain collisions (simulating dune systems). In the areas in the device where gravitationally-driven grain-slurries recycled the sand, the slurries moved with a boundary-layer impeded motion down the chamber walls. Excessive electrostatic charging of the grains during these experiments was prevented by the use of an a.c. corona (created by a Tesla coil) through which the grains passed on every cycle. This created both positive and negative ions which neutralized the triboelectrically-generated grain charges. When the corona was switched on, the velocity of the wall-attached slurries increased by a factor of two as approximately determined by direct observation. What appeared to be a freely-flowing slurry of grains impeded only by intergranular mechanical friction, had obviously been significantly retarded in its motion by electrostatic forces between the grains; with the charging reduced, the grains were able to move past one another without a flow "viscosity" imposed by the Coulombic intergranular forces. A similar phenomenon was observed during microgravity experiments aboard Space Shuttle in USML-1 & USML-2 spacelabs where freely-suspended clouds of sand were being investigated for their potential to for-m aggregates. In this environment, the grains were also charged electrostatically (by natural processes prior to flight), but were free from the intervention of gravity in their interactions. The grains were dispersed into dense clouds by bursts of air turbulence and allowed to form aggregates as the ballistic and turbulent motions damped out. During this

  13. Experimental and analytical investigations of granular materials: Shear flow and convective heat transfer

    Science.gov (United States)

    Ahn, Hojin

    1989-12-01

    Granular materials flowing down an inclined chute were studied experimentally and analytically. Characteristics of convective heat transfer to granular flows were also investigated experimentally and numerically. Experiments on continuous, steady flows of granular materials in an inclined chute were conducted with the objectives of understanding the characteristics of chute flows and of acquiring information on the rheological behavior of granular material flow. Existing constitutive equations and governing equations were used to solve for fully developed chute flows of granular materials, and thus the boundary value problem was formulated with two parameters (the coefficient of restitution between particles, and the chute inclination) and three boundary values at the chute base wall (the values of solid fraction, granular temperature, and mean velocity at the wall). The boundary value problem was numerically solved by the shooting method. These analytical results were also compared with the present experimental values and with the computer simulations by other investigators in their literature. Experiments on heat transfer to granular flows over a flat heating plate were conducted with three sizes of glass beads, polystyrene beads, and mustard seeds. A modification on the existing model for the convective heat transfer was made using the effective Nusselt number and the effective Peclet number, which include the effects of solid fraction variations. The slightly modified model could describe the heat transfer characteristics of both fast and slow flows (supercritical and subcritical). A numerical analysis of the transfer to granular flows was also performed. The results were compared with the present experimental data, and reasonable agreement was found in the comparison.

  14. New quantitative methods for mineral and porosity mapping in clayey materials: application to the compacted bentonites of engineered barriers

    International Nuclear Information System (INIS)

    Pret, D.

    2003-12-01

    Clayey materials are well known for their non permeable properties and their textural changes between the dry and hydrated states. Their porous network is classically investigated in the dry state using bulk measurements. However, the relationship between porosity and mineral spatial heterogeneities in the hydrated state is poorly understood. The textural analysis limits induce some difficulties to understand the migration of solute species into compacted bentonites (as for nuclear waste repository). The goal of this work is to improve the analysis techniques for hydrated clayey materials in order to provide a multi-scale quantitative petrography. The bentonite samples are impregnated using a resin whose properties are close to water ones. The classical petrographic study reveals strong heterogeneities of spatial and size distributions of porosity and minerals. SEM images analysis allows a quantification and a simple mapping of pores and minerals into unaltered bentonites. Nevertheless, as alterations are suspected to happen in the repository context, two methods for the analysis of all types of materials have been also developed. Two specific softwares permits the treatments of autoradiographs and chemical element maps obtained using electron microprobe. The results are quantitative maps highlighting the spatial porosity heterogeneities from the decimetric to the micrometric scales. All pore sizes are taken into account including clay interlayer spaces. Moreover, an accurate mineral mapping is also supplied on millimetric areas with a spatial resolution close to the micrometer. In a widely point of view, this work provides new complementary tools for the textural analysis of fine grained materials and the improvement of migration modelling of solute species. (author)

  15. Subglacial sediment mechanics investigated by computer simulation of granular material

    DEFF Research Database (Denmark)

    Damsgaard, Anders; Egholm, David Lundbek; Tulaczyk, Slawek

    The mechanical properties of subglacial sediments are known to directly influence the stability of ice streams and fast-moving glaciers, but existing models of granular sediment deformation are poorly constrained. In addition, upscaling to generalized mathematical models is difficult due to the m......The mechanical properties of subglacial sediments are known to directly influence the stability of ice streams and fast-moving glaciers, but existing models of granular sediment deformation are poorly constrained. In addition, upscaling to generalized mathematical models is difficult due....... The numerical method is applied to better understand the mechanical properties of the subglacial sediment and its interaction with meltwater. The computational approach allows full experimental control and offers insights into the internal kinematics, stress distribution, and mechanical stability. During...

  16. Numerical investigations on flow dynamics of prismatic granular materials using the discrete element method

    Science.gov (United States)

    Hancock, W.; Weatherley, D.; Wruck, B.; Chitombo, G. P.

    2012-04-01

    The flow dynamics of granular materials is of broad interest in both the geosciences (e.g. landslides, fault zone evolution, and brecchia pipe formation) and many engineering disciplines (e.g chemical engineering, food sciences, pharmaceuticals and materials science). At the interface between natural and human-induced granular media flow, current underground mass-mining methods are trending towards the induced failure and subsequent gravitational flow of large volumes of broken rock, a method known as cave mining. Cave mining relies upon the undercutting of a large ore body, inducement of fragmentation of the rock and subsequent extraction of ore from below, via hopper-like outlets. Design of such mines currently relies upon a simplified kinematic theory of granular flow in hoppers, known as the ellipsoid theory of mass movement. This theory assumes that the zone of moving material grows as an ellipsoid above the outlet of the silo. The boundary of the movement zone is a shear band and internal to the movement zone, the granular material is assumed to have a uniformly high bulk porosity compared with surrounding stagnant regions. There is however, increasing anecdotal evidence and field measurements suggesting this theory fails to capture the full complexity of granular material flow within cave mines. Given the practical challenges obstructing direct measurement of movement both in laboratory experiments and in-situ, the Discrete Element Method (DEM [1]) is a popular alternative to investigate granular media flow. Small-scale DEM studies (c.f. [3] and references therein) have confirmed that movement within DEM silo flow models matches that predicted by ellipsoid theory, at least for mono-disperse granular material freely outflowing at a constant rate. A major draw-back of these small-scale DEM studies is that the initial bulk porosity of the simulated granular material is significantly higher than that of broken, prismatic rock. In this investigation, more

  17. Suitability of granular carbon as an anode material for sediment microbial fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Arends, Jan B.A.; Blondeel, Evelyne; Boon, Nico; Verstraete, Willy [Ghent Univ. (Belgium). Faculty of Bioscience Engineering; Tennison, Steve R. [Mast Carbon International Ltd., Basingstoke, Hampshire (United Kingdom)

    2012-08-15

    Purpose: Sediment microbial fuel cells (S-MFCs) are bio-electrochemical devices that are able to oxidize organic matter directly into harvestable electrical power. The flux of organic matter into the sediment is rather low; therefore, other researchers have introduced plants for a continuous supply of organic matter to the anode electrode. Until now only interconnected materials have been considered as anode materials in S-MFCs. Here, granular carbon materials were investigated for their suitability as an anode material in S-MFCs. Materials and methods: Laboratory microcosms with eight different electrode materials (granules, felts and cloths) were examined with controlled organic matter addition under brackish conditions. Current density, organic matter removal and microbial community composition were monitored using 16S rRNA gene PCR followed by denaturing gradient gel electrophoresis (DGGE). The main parameters investigated were the influence of the amount of electrode material applied to the sediment, the size of the granular material and the electrode configuration. Results and discussion: Felt material had an overall superior performance in terms of current density per amount of applied electrode material; felt and granular anode obtained similar current densities (approx. 50-60 mA m{sup -2}), but felt materials required 29 % less material to be applied. Yet, when growing plants, granular carbon is more suited because it is considered to restore, upon disturbance, the electrical connectivity within the anode compartment. Small granules (0.25-0.5 mm) gave the highest current density compared to larger granules (1-5 mm) of the same material. Granules with a rough surface had a better performance compared to smooth granules of the same size. The different granular materials lead to a selection of distinct microbial communities for each material, as shown by DGGE. Conclusions: Granular carbon is suitable as an anode material for S-MFCs. This opens the possibility

  18. MnFe 2 O 4 /bentonite nano composite as a novel magnetic material ...

    African Journals Online (AJOL)

    It is also found that the presence of bentonite in the magnetic composite has not made any changes in the spinel structure of MnFe2O4. SEM images of the sorbent shows nanocomposite with a uniform structure and nanochannels from 0.3 to 0.8 mμ in diameter having a surface area of 130 m2 g-1. The results also revealed ...

  19. Thermal energy storage characteristics of bentonite-based composite PCMs with enhanced thermal conductivity as novel thermal storage building materials

    International Nuclear Information System (INIS)

    Sarı, Ahmet

    2016-01-01

    Graphical abstract: In this work, novel bentonite-based and form-stable composite phase change materials (Bb-FSPCMs) were produced for LHTES in buildings by impregnation of CA, PEG600, DD and HD with bentonite clay. The microstructures of the compatibility of the Bb-FSPCMs were by using SEM and FT-IR techniques. The DSC results indicated that the produced Bb-FSPCMs composites had suitable phase change temperature of 4–30 °C and good latent heat capacity between 38 and 74 J/g. The TG results demonstrated that all of the fabricated Bb-FSPCMs had good thermal resistance. The Bb-FSPCMs maintained their LHTES properties even after 1000 heating–cooling cycling. The total heating times of the prepared Bb-FSPCMs were reduced noticeably due to their enhanced thermal conductivity after EG (5 wt%) addition. - Highlights: • Bb-FSPCMs were produced by impregnation of CA, PEG600, DD and HD with bentonite. • DSC analysis indicated that Bb-FSPCMs had melting temperature in range of 4–30 °C. • DSC analysis also showed that Bb-FSPCMs had latent heat between 38 and 74 J/g. • The TG analysis demonstrated that Bb-FSPCMs had good thermal resistance. • Thermal conductivity of Bb-FSPCMs were enhanced noticeably with EG (5 wt%) addition. - Abstract: In this work, for latent heat thermal energy storage (LHTES) applications in buildings, bentonite-based form-stable composite phase change materials (Bb-FSPCMs) were produced by impregnation of capric acid (CA), polyethylene glycol (PEG600), dodecanol (DD) and heptadecane (HD) into bentonite clay. The morphological characterization results obtained by scanning electron microscopy (SEM) showed that the bentonite acted as good structural barrier for the organic PCMs homogenously dispersed onto its surface and interlayers. The chemical investigations made by using fourier transform infrared (FT-IR) technique revealed that the attractions between the components of the composites was physical in nature and thus the PCMs were hold

  20. Jamming of three-dimensional prolate granular materials.

    Science.gov (United States)

    Desmond, K; Franklin, Scott V

    2006-03-01

    We have found that the ability of long thin rods to jam into a solidlike state in response to a local perturbation depends upon both the particle aspect ratio and the container size. The dynamic phase diagram in this parameter space reveals a broad transition region separating granular stick-slip and solidlike behavior. In this transition region the pile displays both solid and stick-slip behavior. We measure the force on a small object pulled through the pile, and find the fluctuation spectra to have power law tails with an exponent characteristic of the region. The exponent varies from beta=-2 in the stick-slip region to beta=-1 in the solid region. These values reflect the different origins--granular rearrangements vs dry friction--of the fluctuations. Finally, the packing fraction shows only a slight dependence on container size, but depends on aspect ratio in a manner predicted by mean-field theory and implies an aspect-ratio-independent contact number of =5.25 +/- 0.03.

  1. Microbial occurrence in bentonite-based buffer materials of a final disposal site for low level radioactive waste in Taiwan

    International Nuclear Information System (INIS)

    Chou Fongin; Chen Tzungyuang; Li Chiachin; Wen Hsiaowei

    2011-01-01

    This research addresses the potential of microbial implications in bentonite for use as a buffer and backfill material in final disposal site for low-level radioactive waste (LLRW) in Taiwan, where has a special island-type climate. Microbe activities naturally present in this site were analyzed, and buffer materials (BM) consisted of 100%, 70% or 50% bentonite were prepared for laboratory studies. A total of 39 microbial strains were isolated, and the predominant strains included four bacterial, one yeast and four fungal strains. Growth inhibition was not detected in any tested strain cultured in a radiation field with a dose rate of 0.2 Gy/h. Most of the isolated strains grew under a dose rate of 1.4 Gy/h. The D 10 values of the tested strains ranged from 0.16 to 2.05 kGy. The mycelia of tested fungal strains could spread over 5 cm during six months of inoculation in BM. The spreading activity of the tested bacteria was less than that of the fungi. Moreover, biofilms were observed on the surfaces of the BM. Since a large and diverse population of microbes is present in Taiwan, microbes may contribute to the mobilization of radionuclides in the disposal site. (author)

  2. Research on the mechanical characteristic of the bentonite mixture material under the groundwater environment of Horonobe. 2

    International Nuclear Information System (INIS)

    Takaji, Kazuhiko; Shigeno, Yoshimasa; Simogouchi, Takafumi

    2005-02-01

    In the Horonobe underground research project, various in-situ experiments are conducted in order to confirm the applicability of the Engineered Barrier System (EBS) design techniques shown in H12 report, to understand the long-term effects of EBS, and to improve the reliability of the prediction method. Moreover, since it is assumed that the circumference of Horonobe underground research laboratory is the saline water environment, to understand the mechanical behavior of the bentonite mixture material under the saline water environment is important when influenced in design of in-situ experiments. In this study, unconfined compression tests, consolidated-undrained triaxial compression tests and long-term consolidation tests of the bentonite mixture material were performed using groundwater that is extracted near the Horonobe underground research laboratory, and simulation analyses of EBS over a period of time using the results of laboratory experiments etc. were carried out. Consequently, although compressive strength and the elastic modulus under the saline water environment declined compared with that the fresh water, neither shear deformation behavior under triaxial stress condition nor volume deformation behavior by consolidation test almost had a difference, and it was suggested that there were few possibilities that the saline water had serious influence mechanically also about long-term mechanical behavior. (author)

  3. Studies on the chemical conditions and microstructure in the reference bentonites of alternative buffer materials project (ABM) in Aespoe

    International Nuclear Information System (INIS)

    Muurinen, A.

    2009-06-01

    The chemical and microstructural properties of some bentonites used in the ABM project in Aespoe HRL were studied in laboratory experiments. The aim was to obtain information about the materials before they were used in the field experiment and to test the research methods that will be used when the packages of the field experiment are retrieved. The bentonites of interest were MX-80, Deponit CAN, Asha 505 and Friedland Clay. The pH values in the compacted samples prepared from the clay powders and deionized water were about 8 for MX-80, 7 for Deponit and Asha, and 6.5 for Friedland clay. The Eh values in the compacted MX-80, Asha and Deponit samples varied between 100 mV and -100 mV, and in the Friedland clay from 0 mV to 200 mV. The total porosity, chloride porosity and the microstructure were studied in compacted samples prepared from MX-80, Deponit, Asha and Friedland Clay and equilibrated through filter plates with 0.1 M NaCl solution for 12.5 months in aerobic conditions. The dry densities of the samples were approximately 0.7, 1.0, 1.25 and 1.55 g/cm 3 . XRD and SAXS (Small Angle X-ray Scattering) were used to study the microstructure of the MX-80 and Deponit bentonites. It was obvious that the chloride porosity was lower than the water porosity in all the clays, which indicates the exclusion of anions caused by the negatively charged surfaces. In the XRD measurements on MX-80, Asha and Deponit, the measured basal spaces represented by the diffraction peaks were smaller than the theoretical one assuming a homogenous microstructure. This indicates that there was a substantial amount of water also in the pores, which were not seen by XRD. The SAXS data modelling which considered single discs and stacks of discs proposed that a large fraction of the clay should be considered as single platelets. The fraction of the single discs decreased with the increasing density of the sample. The number of layers in the stacks varied from 4 to 8. By combining the

  4. STUDY OF HYDRODYNAMICS IN FIXED BED OF COMPOSITE GRANULAR MATERIALS

    Directory of Open Access Journals (Sweden)

    Stelian Petrescu

    2010-12-01

    Full Text Available This study aims at the experimental determination of pressure drop and friction factor at gas flow through fixed beds of granular silica gel, alumina and activated carbon, and establishment of an equation containing a modified friction factor Fm to calculate pressure drop. In order to calculate the modified friction factor, an equation was suggested.The experimental values for pressure drop and friction factor were determined using spherical grains of silica gel, cylindrical grains of alumina and silica gel, alumina and activated carbon impregnated with calcium chloride. By means of the suggested equation, the values of pressure drop in fixed bed were calculated and compared with the experimental values. A good agreement between the predicted and experimental data is noticed.

  5. Hydro-mechanical behaviour of bentonite-sand mixture used as sealing materials in radioactive waste disposal galleries

    International Nuclear Information System (INIS)

    Saba, Simona

    2013-01-01

    In order to verify the effectiveness of the geological high-level radioactive waste disposal, the French Institution of Radiation protection and Nuclear Safety (IRSN) has implemented the SEALEX project to control the long-term performance of swelling clay-based sealing systems, and to which this work is closely related. Within this project, In-situ tests are carried out on compacted bentonite-sand mixture in natural conditions and in a representative scale. This material is one of the most appropriate sealing materials because of its low permeability and good swelling capacity. Once installed, this material will be hydrated by water from the host-rock and start swelling to close all gaps in the system, in particular the internal pores, rock fractures and technological voids. Afterwards, swelling pressure will develop. In the present work, laboratory experiments were performed to investigate the sealing properties under this complex hydro-mechanical conditions taking into consideration the effect of technological voids. The microstructure of the material in its initial state was first examined by microfocus X-ray computed tomography (μCT). This allowed identification of the distribution of grains of sand and bentonite as well as the pores in the sample. Macro-pores are found concentrated at the periphery of the sample and between the grains of sand, which could affect in the short term the permeability. The hydration of the same material in limited swelling conditions was then observed by 2D photography and 3D μCT. The swelling mechanism with bentonite gel production, the swelling kinetics, the density decrease and the homogenisation of the material were analyzed. The hydration in the conditions of prevented swelling was also studied by swelling pressure tests with radial and axial measurements of swelling pressure. The difference found between the axial and radial swelling pressures suggested the presence of an anisotropic microstructure. Mock-up tests at a 1

  6. Hydro-mechanical behaviour of bentonite-sand mixture used as sealing materials in radioactive waste disposal galleries

    International Nuclear Information System (INIS)

    Saba, Simona

    2013-01-01

    In order to verify the effectiveness of the geological high-level radioactive waste disposal, the French Institute for Radiation protection and Nuclear Safety (IRSN) has implemented the SEALEX project to control the long-term performance of swelling clay-based sealing systems, and to which this work is closely related. Within this project, In-situ tests are carried out on compacted bentonite-sand mixture in natural conditions and in a representative scale. This material is one of the most appropriate sealing materials because of its low permeability and good swelling capacity. Once installed, this material will be hydrated by water from the host-rock and start swelling to close all gaps in the system, in particular the internal pores, rock fractures and technological voids. Afterwards, swelling pressure will develop. In the present work, laboratory experiments were performed to investigate the sealing properties under these complex hydro-mechanical conditions taking into consideration the effect of technological voids. The microstructure of the material in its initial state was first examined by microfocus X-ray computed tomography (μCT). This allowed identification of the distribution of grains of sand and bentonite as well as the pores in the sample. Macro-pores are found concentrated at the periphery of the sample and between the grains of sand, which could affect in the short term the permeability. The hydration of the same material in limited swelling conditions was then observed by 2D photography and 3D μCT. The swelling mechanism with bentonite gel production, the swelling kinetics, the density decrease and the homogenisation of the material were analyzed. The hydration in the conditions of prevented swelling was also studied by swelling pressure tests with radial and axial measurements of swelling pressure. The difference found between the axial and radial swelling pressures suggested the presence of an anisotropic microstructure. Mock-up tests at a 1

  7. Bentonite erosion - Laboratory studies

    International Nuclear Information System (INIS)

    Jansson, Mats

    2010-01-01

    Document available in extended abstract form only. Bentonite clay is proposed as buffer material in the KBS-3 concept of storing spent nuclear fuel. Since the clay is plastic it will protect the canisters containing the spent fuel from movements in the rock. Furthermore, the clay will expand when taking up water, become very compact and hence limit the transport of solutes to and from the canister to only diffusion. The chemical stability of the bentonite barrier is of vital importance. If much material would be lost the barrier will lose its functions. As a side effect, lots of colloids will be released which may facilitate radionuclide transport in case of a breach in the canister. There are scenarios where during an ice age fresh melt water may penetrate down to repository depths with relatively high flow rates and not mix with older waters of high salinity. Under such conditions bentonite colloids will be more stable and there is a possibility that the bentonite buffer would start to disperse and bentonite colloids be carried away by the passing water. This work is a part of a larger project called Bentonite Erosion, initiated and supported by SKB. In this work several minor experiments have been performed in order to investigate the influence of for instance di-valent cations, gravity, etc. on the dispersion behaviour of bentonite and/or montmorillonite. A bigger experiment where the real situation was simulated using an artificial fracture was conducted. Two Plexiglas slabs were placed on top of each other, separated by plastic spacers. Bentonite was placed in a container in contact with a fracture. The bentonite was water saturated before deionized water was pumped through the fracture. The evolution of the bentonite profile in the fracture was followed visually. The eluate was collected in five different slots at the outlet side and analyzed for colloid concentration employing Photon Correlation Spectroscopy (PCS) and a Single Particle Counter (SPC). Some

  8. Preparation and thermal characterization of oxalic acid dihydrate/bentonite composite as shape-stabilized phase change materials for thermal energy storage

    Science.gov (United States)

    Han, Lipeng; Xie, Shaolei; Sun, Jinhe; Jia, Yongzhong

    2017-03-01

    Oxalic acid dihydrate (OAD) which has very high initial phase transition enthalpy is a promising phase change material (PCM). In this paper, shape-stabilized composite PCMs composed of OAD and bentonite were prepared by a facile blending method to overcome the problem of leakage. FT-IR results indicated the interactions between OAD and bentonite, such as the capillary force and the hydrogen bonding, resulting in the confined crystallization process. As a result, the OAD was confined to be amorphous. The thermogravimetric analysis and scanning electron microscope results showed that sample had the best coating effect when the amount of bentonite was 17.7%. The differential scanning calorimetry analyses demonstrated that a decrease in the OAD content was accompanied by a continuous decrease in the melting point and phase change enthalpy of the composites.

  9. Effect of Anisotropy on the Resilient Behaviour of a Granular Material in Low Traffic Pavement.

    Science.gov (United States)

    Jing, Peng; Nowamooz, Hossein; Chazallon, Cyrille

    2017-12-03

    Granular materials are often used in pavement structures. The influence of anisotropy on the mechanical behaviour of granular materials is very important. The coupled effects of water content and fine content usually lead to more complex anisotropic behaviour. With a repeated load triaxial test (RLTT), it is possible to measure the anisotropic deformation behaviour of granular materials. This article initially presents an experimental study of the resilient repeated load response of a compacted clayey natural sand with three fine contents and different water contents. Based on anisotropic behaviour, the non-linear resilient model (Boyce model) is improved by the radial anisotropy coefficient γ ₃ instead of the axial anisotropy coefficient γ ₁. The results from both approaches ( γ ₁ and γ ₃) are compared with the measured volumetric and deviatoric responses. These results confirm the capacity of the improved model to capture the general trend of the experiments. Finally, finite element calculations are performed with CAST3M in order to validate the improvement of the modified Boyce model (from γ ₁ to γ ₃). The modelling results indicate that the modified Boyce model with γ ₃ is more widely available in different water contents and different fine contents for this granular material. Besides, based on the results, the coupled effects of water content and fine content on the deflection of the structures can also be observed.

  10. REFINEMENT AND GRANULATING OF COHERENT-GRANULAR MATERIALS IN MACHINES OF ROLL TYPE

    Directory of Open Access Journals (Sweden)

    E. B. Lozhechnikov

    2006-01-01

    Full Text Available The way of selective break of heterogeneous compositions, in particular slags of copper-smelting production and also granular metal-containing powder materials, is based and developed. Calibration of the rolls, providing contrilled granulating of metal-containing powders by rolling.

  11. Measurements of Acoustic Properties of Porous and Granular Materials and Application to Vibration Control

    Science.gov (United States)

    Park, Junhong; Palumbo, Daniel L.

    2004-01-01

    For application of porous and granular materials to vibro-acoustic controls, a finite dynamic strength of the solid component (frame) is an important design factor. The primary goal of this study was to investigate structural vibration damping through this frame wave propagation for various poroelastic materials. A measurement method to investigate the vibration characteristics of the frame was proposed. The measured properties were found to follow closely the characteristics of the viscoelastic materials - the dynamic modulus increased with frequency and the degree of the frequency dependence was determined by its loss factor. The dynamic stiffness of hollow cylindrical beams containing porous and granular materials as damping treatment was measured also. The data were used to extract the damping materials characteristics using the Rayleigh-Ritz method. The results suggested that the acoustic structure interaction between the frame and the structure enhances the dissipation of the vibration energy significantly.

  12. Granular patterns

    CERN Document Server

    Aranson, Igor S

    2009-01-01

    This title presents a review of experiments and novel theoretical concepts needed to understand the mechanisms of pattern formation in granular materials. An effort is made to connect concepts and ideas developed in granular physics with new emergent fields, especially in biology, such as cytoskeleton dynamics.

  13. Prediction for swelling characteristics of compacted bentonite

    International Nuclear Information System (INIS)

    Komine, H.; Ogata, N.

    1996-01-01

    Compacted bentonites are attracting greater attention as back-filling (buffer) materials for high-level nuclear waste repositories. For this purpose, it is very important to quantitatively evaluate the swelling characteristics of compacted bentonite. New equations for evaluating the relationship between the swelling deformation of compacted bentonite and the distance between two montmorillonite layers are derived. New equations for evaluating the ion concentration of pore water and the specific surface of bentonite, which significantly influence the swelling characteristics of compacted bentonite, are proposed. Furthermore, a prediction method for the swelling characteristics of compacted bentonite is presented by combining the new equations with the well-known theoretical equations of repulsive and attractive forces between two montmorillonite layers. The applicability of this method was investigated by comparing the predicted results with laboratory test results on the swelling deformation and swelling pressure of compacted bentonites. (author) 31 refs., 8 tabs., 12 figs

  14. Terminal velocity of liquids and granular materials dispersed by a high explosive

    Science.gov (United States)

    Loiseau, J.; Pontalier, Q.; Milne, A. M.; Goroshin, S.; Frost, D. L.

    2018-04-01

    The explosive dispersal of a layer of solid particles or a layer of liquid surrounding a spherical high-explosive charge generates a turbulent, multiphase flow. Shock compression of the material layer during the initial acceleration may partially consolidate the material, leading to the formation of jet-like structures when the layer fragments and sheds particles upon release. Similarly, release of a shock-compressed liquid shell causes the nucleation of cavitation sites, leading to the radial breakup of the shell and the formation of jets upon expansion. In the current study, a wide variety of granular materials and liquids were explosively dispersed. The maximum terminal jet tip or shell velocity was measured using high-speed videography. Charges were constructed using thin-walled glass bulbs of various diameters and contained a central C-4 charge surrounded by the material to be dispersed. This permitted variation of the ratio of material mass to charge mass (M/C) from 4 to 300. Results indicated that material velocity broadly correlates with predictions of the Gurney model. For liquids, the terminal velocity was accurately predicted by the Gurney model. For granular materials, Gurney over-predicted the terminal velocity by 25-60%, depending on the M/C ratio, with larger M/C values exhibiting larger deficits. These deficits are explained by energy dissipation during the collapse of voids in the granular material bed. Velocity deficits were insensitive to the degree of jetting and granular material properties. Empirical corrections to the Gurney model are presented with improved agreement with the dry powder experimental velocities.

  15. Terminal velocity of liquids and granular materials dispersed by a high explosive

    Science.gov (United States)

    Loiseau, J.; Pontalier, Q.; Milne, A. M.; Goroshin, S.; Frost, D. L.

    2018-05-01

    The explosive dispersal of a layer of solid particles or a layer of liquid surrounding a spherical high-explosive charge generates a turbulent, multiphase flow. Shock compression of the material layer during the initial acceleration may partially consolidate the material, leading to the formation of jet-like structures when the layer fragments and sheds particles upon release. Similarly, release of a shock-compressed liquid shell causes the nucleation of cavitation sites, leading to the radial breakup of the shell and the formation of jets upon expansion. In the current study, a wide variety of granular materials and liquids were explosively dispersed. The maximum terminal jet tip or shell velocity was measured using high-speed videography. Charges were constructed using thin-walled glass bulbs of various diameters and contained a central C-4 charge surrounded by the material to be dispersed. This permitted variation of the ratio of material mass to charge mass ( M/ C) from 4 to 300. Results indicated that material velocity broadly correlates with predictions of the Gurney model. For liquids, the terminal velocity was accurately predicted by the Gurney model. For granular materials, Gurney over-predicted the terminal velocity by 25-60%, depending on the M/ C ratio, with larger M/ C values exhibiting larger deficits. These deficits are explained by energy dissipation during the collapse of voids in the granular material bed. Velocity deficits were insensitive to the degree of jetting and granular material properties. Empirical corrections to the Gurney model are presented with improved agreement with the dry powder experimental velocities.

  16. Left-handed materials in metallic magnetic granular composites

    International Nuclear Information System (INIS)

    Chui, S.T.; Lin, Z.F.; Hu, L.-B.

    2003-01-01

    There is recently interests in the 'left-handed' materials. In these materials the direction of the wave vector of electromagnetic radiation is opposite to the direction of the energy flow. We present simple arguments that suggests that magnetic composites can also be left-handed materials. However, the physics involved seems to be different from the original argument. In our argument, the imaginary part of the dielectric constant is much larger than the real part, opposite to the original argument

  17. Mechanical properties of granular materials: A variational approach to grain-scale simulations

    Energy Technology Data Exchange (ETDEWEB)

    Holtzman, R.; Silin, D.B.; Patzek, T.W.

    2009-01-15

    The mechanical properties of cohesionless granular materials are evaluated from grain-scale simulations. A three-dimensional pack of spherical grains is loaded by incremental displacements of its boundaries. The deformation is described as a sequence of equilibrium configurations. Each configuration is characterized by a minimum of the total potential energy. This minimum is computed using a modification of the conjugate gradient algorithm. Our simulations capture the nonlinear, path-dependent behavior of granular materials observed in experiments. Micromechanical analysis provides valuable insight into phenomena such as hysteresis, strain hardening and stress-induced anisotropy. Estimates of the effective bulk modulus, obtained with no adjustment of material parameters, are in agreement with published experimental data. The model is applied to evaluate the effects of hydrate dissociation in marine sediments. Weakening of the sediment is quantified as a reduction in the effective elastic moduli.

  18. Application of mixed based membrane technology from component materials bintaro, zeolite and bentonite to reduction of songket waste liquid cloth

    Science.gov (United States)

    Dahlan, Muhammad Hatta; Saleh, Abdullah; Asip, Faisol; Makmun, Akbar; Defi

    2017-11-01

    Application of membrane technology based on clay mixture, Activated Carbon from Bintaro, Zeolite and Bentonit to process the waste water of Songket cloth is Palembang traditionally cloth. The applied research is into the superior field of industrial and household waste processing with membrane ceramic technology. The objective of this research is to design the liquid waste separation tool of jumputan cloth using better and simpler ceramic membrane so that it can help the artisans of Palembang songket or songket in processing the waste in accordance with the standard of environmental quality standard (BML) and Pergub Sumsel no. 16 in 2005. The specific target to be achieved can decrease the waste of cloth jumputan in accordance with applicable environmental quality standards the method used in achieving the objectives of this study using 2 processes namely the adsorption process using activated carbon and the separation process using a ceramic membrane based on the composition of the mixture. The activated carbon from bintaro seeds is expected to decrease the concentration of liquid waste of Songket cloth. Bintaro seeds are non-edible fruits where the composition contains organic ingredients that can absorb because contains dyes and filler metals. The process of membranization in the processing is expected to decrease the concentration of waste better and clear water that can be used as recycled water for household use. With the composition of a mixture of clay-based materials: zeolite, bentonit, activated carbon from bintaro seeds are expected Find the solution and get the novelty value in the form of patent in this research

  19. Static Friction Phenomena in Granular Materials: Coulomb Law vs. Particle Geometry

    OpenAIRE

    Poeschel, T.; Buchholtz, V.

    1993-01-01

    The static as well as the dynamic behaviour of granular material are determined by dynamic {\\it and} static friction. There are well known methods to include static friction in molecular dynamics simulations using scarcely understood forces. We propose an Ansatz based on the geometrical shape of nonspherical particles which does not involve an explicit expression for static friction. It is shown that the simulations based on this model are close to experimental results.

  20. Numerical Simulation on Dense Packing of Granular Materials by Container Oscillation

    OpenAIRE

    Jun Liu; Dongxu You

    2013-01-01

    The packing of granular materials is a basic and important problem in geomechanics. An approach, which generates dense packing of spheres confined in cylindrical and cuboidal containers in three steps, is introduced in this work. A loose packing structure is first generated by means of a reference lattice method. Then a dense packing structure is obtained in a container by simulating dropping of particles under gravitational forces. Furthermore, a scheme that makes the bottom boundary fluctua...

  1. A numerical toolkit to understand the mechanics of partially saturated granular materials

    OpenAIRE

    Roux , Jean-Noël

    2015-01-01

    ``Focus on Fluids'' section; International audience; The mechanisms by which a wetting, non-saturating liquid bestows macroscopic cohesion and strength to a granular material are usually not accessible to micromechanical investigations for saturations exceeding the pendular regime of isolated menisci, easily studied by discrete element models. The " JFM-Rapids " paper (vol. 762, R5, 2015) by Delenne, Richefeu and Radja¨ıRadja¨ı, exploiting a multiphase Lattice Boltzmann approach, pioneers the...

  2. Moisture distribution computed from electrical impedance tomographic data of a bentonite clay/sand material

    International Nuclear Information System (INIS)

    Strobel, G.S.

    1995-11-01

    Moisture contents values were calculated from electrical impedance-computed tomography measurements and compared with thermocouple psychrometer moisture values. The measurements were taken, in situ and under isothermal conditions, in a bentonite clay/sand packed borehole at the Underground Research Laboratory. Two sets of impedances moisture contents were calculated from the impedance valves--independent of each other. For one set, impedance measurements were fitted to the psychrometer moisture values in a least-squares fit to a generalized calibration curve and, for the second set, an impedance-moisture relationship from laboratory calibrations was applied. The impedance-computed moisture content data showed low scatter and the trends were consistent between the three sets of values. However, the moisture content data computed from the calibration curve were more consistent with those expected from physical arguments. The moisture values from the psychrometer readings were offset and, consequently, so were those produced after applying the fitting strategy. Internal redistribution of moisture appears to have had a more significant effect on the system than did inflow at the boundary. Inflow did cause a significant change but this was localized, during this period, to the outer ∼ 0.05 m of the test hole. No comment was made as to what internal processes caused these responses. (author) 9 refs., 2 tabs., 5 figs

  3. Advances in the simulation and automated measurement of well-sorted granular material: 1. Simulation

    Science.gov (United States)

    Daniel Buscombe,; Rubin, David M.

    2012-01-01

    1. In this, the first of a pair of papers which address the simulation and automated measurement of well-sorted natural granular material, a method is presented for simulation of two-phase (solid, void) assemblages of discrete non-cohesive particles. The purpose is to have a flexible, yet computationally and theoretically simple, suite of tools with well constrained and well known statistical properties, in order to simulate realistic granular material as a discrete element model with realistic size and shape distributions, for a variety of purposes. The stochastic modeling framework is based on three-dimensional tessellations with variable degrees of order in particle-packing arrangement. Examples of sediments with a variety of particle size distributions and spatial variability in grain size are presented. The relationship between particle shape and porosity conforms to published data. The immediate application is testing new algorithms for automated measurements of particle properties (mean and standard deviation of particle sizes, and apparent porosity) from images of natural sediment, as detailed in the second of this pair of papers. The model could also prove useful for simulating specific depositional structures found in natural sediments, the result of physical alterations to packing and grain fabric, using discrete particle flow models. While the principal focus here is on naturally occurring sediment and sedimentary rock, the methods presented might also be useful for simulations of similar granular or cellular material encountered in engineering, industrial and life sciences.

  4. A new perspective of particle adsorption: Dispersed oil and granular materials interactions in simulated coastal environment.

    Science.gov (United States)

    Meng, Long; Bao, Mutai; Sun, Peiyan

    2017-09-15

    This study, adsorption behaviors of dispersed oil in seawaters by granular materials were explored in simulation environment. We quantitatively demonstrated the dispersed oil adsorbed by granular materials were both dissolved petroleum hydrocarbons (DPHs) and oil droplets. Furthermore, DPHs were accounted for 42.5%, 63.4%, and 85.2% (35.5% was emulsion adsorption) in the adsorption of dispersed oil by coastal rocks, sediments, and bacterial strain particles respectively. Effects of controlling parameters, such as temperature, particle size and concentration on adsorption of petroleum hydrocarbons were described in detail. Most strikingly, adsorption concentration was followed a decreasing order of bacterial strain (0.5-2μm)>sediments (0.005-0.625mm)>coastal rocks (0.2-1cm). With particle concentration or temperature increased, adsorption concentration increased for coastal rocks particle but decreased for sediments particle. Besides, particle adsorption rate of petroleum hydrocarbons (n-alkanes and PAHs) was different among granular materials during 60 days. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. Exact Solutions of the Hierarchical Korteweg-de Vries Equation of Micro structured Granular Materials

    International Nuclear Information System (INIS)

    Abourabia, A.M.; El-Danaf, T.S.; Morad, A.M.

    2008-01-01

    The problem under consideration are related to wave propagation in micro structured materials, characterized by higher-order nonlinear and higher-order dispersive effects; particularly, the wave propagation in dilatant granular materials. In the present paper the model equation is solved analytically by exact method called Jacobi elliptic method. The types of solutions are defined and discussed over a wide range of material parameters (two dispersion parameters and one microstructure parameter). The dispersion properties and the relation between group and phase velocities of the model equation are studied. The diagrams are drawn to illustrate the physical properties of the exact solutions

  6. Partitioning of fresh crude oil between floating, dispersed and sediment phases: Effect of exposure order to dispersant and granular materials.

    Science.gov (United States)

    Boglaienko, Daria; Tansel, Berrin

    2016-06-15

    When three or more high and low energy substrates are mixed, wetting order can significantly affect the behavior of the mixture. We analyzed the phase distribution of fresh floating Louisiana crude oil into dispersed, settled and floating phases depending on the exposure sequence to Corexit 9500A (dispersant) and granular materials. In the experiments artificial sea water at salinity 34‰ was used. Limestone (2.00-0.300 mm) and quartz sand (0.300-0.075 mm) were used as the natural granular materials. Dispersant Corexit 9500A increased the amount of dispersed oil up to 33.76 ± 7.04%. Addition of granular materials after the dispersant increased dispersion of oil to 47.96 ± 1.96%. When solid particles were applied on the floating oil before the dispersant, oil was captured as oil-particle aggregates and removed from the floating layer. However, dispersant addition led to partial release of the captured oil, removing it from the aggregated form to the dispersed and floating phases. There was no visible oil aggregation with the granular materials when quartz or limestone was at the bottom of the flask before the addition of oil and dispersant. The results show that granular materials can be effective when applied from the surface for aggregating or dispersing oil. However, the granular materials in the sediments are not effective neither for aggregating nor dispersing floating oil. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. COMPORTAMIENTO RESILIENTE DE MATERIALES GRANULARES EN PAVIMENTOS FLEXIBLES: ESTADO DEL CONOCIMIENTO RESILIENT BEHAVIOR OF GRANULAR MATERIALS IN FLEXIBLE PAVEMENTS: STATE OF THE ART

    Directory of Open Access Journals (Sweden)

    Hugo Alexander Rondón Quintana

    2007-07-01

    Full Text Available Los vehículos que circulan sobre una estructura de pavimento inducen ciclos de carga y descarga que generan dentro de las capas granulares deformaciones recuperables (resilientes y permanentes (plásticas. La ingeniería de pavimentos ha venido desarrollando estudios desde la década de los 60 con el fin de intentar comprender el comportamiento elastoplástico que experimentan materiales granulares cuando conforman capas de base y subbase en estructuras flexibles. La mayor parte de las investigaciones que se han realizado en esta área se han concentrado en estudiar su comportamiento resiliente. El estado del conocimiento de estudios desarrollados para medir la respuesta resiliente y la deformación permanente en materiales granulares es presentado en dos artículos por separado. En este primer artículo se presenta la forma como ha sido estudiado el comportamiento resiliente de materiales granulares y se discuten los factores que influyen en dicho comportamiento. Al final del artículo se presenta la evolución de las ecuaciones matemáticas desarrolladas a partir de resultados de estudios teóricos y experimentales. Un estado del conocimiento sobre el fenómeno de deformación permanente es presentado en un segundo artículo.When vehicles move on a pavement structure, they induce load cycles that generate resilient and permanent strains inside granular layers. Since the 60's, pavement engineering has developed studies in order to understand the elasto-plastic behavior that granular materials experiment on base and sub-base layers of flexible pavements. Most of the researches that have been made in this area have concentrated in studying their resilient behavior. A state of the art about the behavior of granular materials in flexible pavements is presented in two separate papers. This first paper tries on resilient stress-strain characteristics of such materials. The mathematical equations found in the literature to predict the resilient

  8. Modelling transient 3D multi-phase criticality in fluidised granular materials - the FETCH code

    International Nuclear Information System (INIS)

    Pain, C.C.; Gomes, J.L.M.A.; Eaton, M.D.; Ziver, A.K.; Umpleby, A.P.; Oliveira, C.R.E. de; Goddard, A.J.H.

    2003-01-01

    The development and application of a generic model for modelling criticality in fluidised granular materials is described within the Finite Element Transient Criticality (FETCH) code - which models criticality transients in spatial and temporal detail from fundamental principles, as far as is currently possible. The neutronics model in FETCH solves the neutron transport in full phase space with a spherical harmonics angle of travel representation, multi-group in neutron energy, Crank Nicholson based in time stepping, and finite elements in space. The fluids representation coupled with the neutronics model is a two-fluid-granular-temperature model, also finite element fased. A separate fluid is used to represent the liquid/vapour gas and the solid fuel particle phases, respectively. Particle-particle, particle-wall interactions are modelled using a kinetic theory approach on an analogy between the motion of gas molecules subject to binary collisions and granular flows. This model has been extensively validated by comparison with fluidised bed experimental results. Gas-fluidised beds involve particles that are often extremely agitated (measured by granular temperature) and can thus be viewed as a particularly demanding application of the two-fluid model. Liquid fluidised systems are of criticality interest, but these can become demanding with the production of gases (e.g. radiolytic and water vapour) and large fluid/particle velocities in energetic transients. We present results from a test transient model in which fissile material ( 239 Pu) is presented as spherical granules subsiding in water, located in a tank initially at constant temperature and at two alternative over-pressures in order to verify the theoretical model implemented in FETCH. (author)

  9. A thermomechanical constitutive model for cemented granular materials with quantifiable internal variables. Part II - Validation and localization analysis

    Science.gov (United States)

    Das, Arghya; Tengattini, Alessandro; Nguyen, Giang D.; Viggiani, Gioacchino; Hall, Stephen A.; Einav, Itai

    2014-10-01

    We study the mechanical failure of cemented granular materials (e.g., sandstones) using a constitutive model based on breakage mechanics for grain crushing and damage mechanics for cement fracture. The theoretical aspects of this model are presented in Part I: Tengattini et al. (2014), A thermomechanical constitutive model for cemented granular materials with quantifiable internal variables, Part I - Theory (Journal of the Mechanics and Physics of Solids, 10.1016/j.jmps.2014.05.021). In this Part II we investigate the constitutive and structural responses of cemented granular materials through analyses of Boundary Value Problems (BVPs). The multiple failure mechanisms captured by the proposed model enable the behavior of cemented granular rocks to be well reproduced for a wide range of confining pressures. Furthermore, through comparison of the model predictions and experimental data, the micromechanical basis of the model provides improved understanding of failure mechanisms of cemented granular materials. In particular, we show that grain crushing is the predominant inelastic deformation mechanism under high pressures while cement failure is the relevant mechanism at low pressures. Over an intermediate pressure regime a mixed mode of failure mechanisms is observed. Furthermore, the micromechanical roots of the model allow the effects on localized deformation modes of various initial microstructures to be studied. The results obtained from both the constitutive responses and BVP solutions indicate that the proposed approach and model provide a promising basis for future theoretical studies on cemented granular materials.

  10. Mineralogical and chemical characterization of various bentonite and smectite-rich clay materials Part A: Comparison and development of mineralogical characterization methods Part B: Mineralogical and chemical characterization of clay materials

    International Nuclear Information System (INIS)

    Kumpulainen, S.; Kiviranta, L.

    2010-06-01

    Mineralogy is an essential issue in understanding thermo-hydro-mechanical-chemical (THMC) behavior of bentonite materials. Mineralogy affects, among others, chemical composition of pore water, susceptibility for erosion, and transport of radionuclides. Consequently, mineralogy affects the designs of the buffer and backfill components. The objective of this work was to implement and develop mineralogical and chemical methods for characterization of reference clays considered for use as buffer and backfill materials in nuclear waste disposal. In this work, different methods were tested, compared, developed, and best available techniques selected. An additional aim was to characterize reference materials that are used in various nuclear waste disposal supporting studies, e.g., the SKB's alternative buffer material (ABM) experiment. Materials studied included three Wyoming-bentonites, two bentonites from Milos, four bentonites from Kutch district, and two Friedland clays. Minerals were identified using x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and polarizing microscopy. Mineralogical composition was estimated using Rietveld-analysis. Chemical methods were used to support and validate mineralogical interpretation. Total chemical composition was determined from decomposed samples using spectrometry (ICP-AES) and combustion (Leco-S, Leco-C). Ferric and ferrous iron species were distinguished titrimetrically and the amount of soluble sulphate was determined using ion chromatography. In addition, cation exchange capacity and original exchangeable cations were determined. Chemical composition of fine (<2 μ m) fractions and poorly crystalline Fe-, Al- and Si-phases determined by selective extractions were used in structural calculations of smectite. XRD is a basic method for all mineralogical characterization, but it is insensitive for detecting trace minerals and variations in the structural chemical composition of clay minerals. Polarizing

  11. Effect of cohesion on local compaction and granulation of sheared soft granular materials

    Directory of Open Access Journals (Sweden)

    Roy Sudeshna

    2017-01-01

    Full Text Available This paper results from an ongoing investigation of the effect of cohesion on the compaction of sheared soft wet granular materials. We compare dry non-cohesive and wet moderately-to-strongly cohesive soft almost frictionless granular materials and report the effect of cohesion between the grains on the local volume fraction. We study this in a three dimensional, unconfined, slowly sheared split-bottom ring shear cell, where materials while sheared are subject to compression under the confining weight of the material above. Our results show that inter-particle cohesion has a considerable impact on the compaction of soft materials. Cohesion causes additional stresses, due to capillary forces between particles, leading to an increase in volume fraction due to higher compaction. This effect is not visible in a system of infinitely stiff particles. In addition, acting oppositely, we observe a general decrease in volume fraction due to increased cohesion for frictional particle, which we attribute to the role of contact friction that enhances dilation.

  12. Gas Transport in Bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Villar, M. V.; Gutierre-Rodrigo, V.; Martin, P. I.; Romero, F. J.; Barcala, J. M.

    2013-07-01

    The gas permeability of the Spanish FEBEX bentonite compacted at dry densities of between 1.4 and 1.8 g/cm{sup 3} with high water contents was measured for different confining, injection and back pressures. The results were compared with results obtained in previous investigations for lower degrees of saturation. It was checked that gas permeability was greatly affected by dry density, decreasing about three orders of magnitude when it increased from 1.5 to 1.8 g/cm{sup 3} for similar water content. The increase of water content caused also a decrease in gas permeability. It was found that both gas permeability and the relative gas permeability were mainly related to the accessible porosity. These relationships could be fitted to potential expressions with exponents between 3 and 4, as well as the relationship between intrinsic permeability and void ratio. For gas pressures below 1.2 MPa no effect of the injection or confining pressures on the value of permeability was detected. For a given confining pressure the permeability value decreased as the effective pressure increased, especially if the increase in effective pressure was due to a decrease in gas back pressure. It was checked that the Klinkenberg effect was not significant for this material in the range of pressures applied in the tests. The gas breakthrough pressure values in FEBEX saturated bentonite were determined for different dry densities. They increased clearly with dry density and were always higher than the swelling pressure of the bentonite. In high density samples gas flow tended to stop abruptly after breakthrough, whereas in lower density samples gas flow decreased gradually until a given pressure gradient was reached. The permeabilities computed after breakthrough (which usually did not stabilise) were inversely related to dry density. This would indicate that, even if the flow took place predominantly through preferential pathways that sometimes closed quickly after breakthrough and others

  13. Gas Transport in Bentonite

    International Nuclear Information System (INIS)

    Villar, M. V.; Gutierrez-Rodrigo, V.; Martin, P. L.; Romero, F. J.; Barcala, J. M.

    2013-01-01

    The gas permeability of the Spanish FEBEX bentonite compacted at dry densities of between 1.4 and 1.8 g/cm 3 with high water contents was measured for different confining, injection and back pressures. The results were compared with results obtained in previous investigations for lower degrees of saturation. It was checked that gas permeability was greatly affected by dry density, decreasing about three orders of magnitude when it increased from 1.5 to 1.8 g/cm 3 for similar water content. The increase of water content caused also a decrease in gas permeability. It was found that both gas permeability and the relative gas permeability were mainly related to the accessible porosity. These relationships could be fitted to potential expressions with exponents between 3 and 4, as well as the relationship between intrinsic permeability and void ratio. For gas pressures below 1.2 MPa no effect of the injection or confining pressures on the value of permeability was detected. For a given confining pressure the permeability value decreased as the effective pressure increased, especially if the increase in effective pressure was due to a decrease in gas back pressure. It was checked that the Klinkenberg effect was not significant for this material in the range of pressures applied in the tests. The gas breakthrough pressure values in FEBEX saturated bentonite were determined for different dry densities. They increased clearly with dry density and were always higher than the swelling pressure of the bentonite. In high density samples gas flow tended to stop abruptly after breakthrough, whereas in lower density samples gas flow decreased gradually until a given pressure gradient was reached. The permeabilities computed after breakthrough (which usually did not stabilise) were inversely related to dry density. This would indicate that, even if the flow took place predominantly through preferential pathways that sometimes closed quickly after breakthrough and others remained

  14. Deformación permanente de materiales granulares en pavimentos flexibles: estado del conocimiento Permanent strain of granular materials in flexible pavements: state of the art

    Directory of Open Access Journals (Sweden)

    Hugo Alexánder Rondón

    2009-01-01

    Full Text Available Diversos estudios han sido desarrollados en el área de los pavimentos para comprender el comportamiento elastoplástico que experimentan materiales granulares bajo carga cíclica. Este es el segundo de dos artículos que presentan el estado del conocimiento de investigaciones desarrolladas en esta área. Basado en una amplia revisión bibliográfica, este artículo da cuenta de la forma como ha sido estudiado el fenómeno de deformación permanente en materiales granulares empleados para conformar capas de base y sub-base de estructuras de pavimentos flexibles. Además, se exponen y se discuten los factores que afectan la resistencia a la deformación permanente y la evolución de las ecuaciones matemáticas desarrolladas para predecir la deformación que experimentan estos materiales bajo carga cíclica. Un estado del conocimiento sobre el comportamiento resiliente de estos materiales es presentado en el primer artículo (Rondón y Reyes, 2007.Several studies have been conducted in pavement field for trying to understand the elastoplastic behavior experienced by granular materials under a cyclic load. This is the second out of two articles which show state-of-the-art of researches conducted in this field. Based on a wide literature review, this article accounts for the way how permanent strain phenomenon has been studied in granular materials used for creating base and sub-base layers of flexible pavement structures. Besides, this article displays and discusses factors which affect resistance to permanent strain and evolution of mathematical equations developed for predicting that strain experienced by these materials under a cyclic load. A state-of-the-art about resilient behavior of these materials has been presented in the first article (Rondón and Reyes, 2007.

  15. An automatic granular structure generation and finite element analysis of heterogeneous semi-solid materials

    International Nuclear Information System (INIS)

    Sharifi, Hamid; Larouche, Daniel

    2015-01-01

    The quality of cast metal products depends on the capacity of the semi-solid metal to sustain the stresses generated during the casting. Predicting the evolution of these stresses with accuracy in the solidification interval should be highly helpful to avoid the formation of defects like hot tearing. This task is however very difficult because of the heterogeneous nature of the material. In this paper, we propose to evaluate the mechanical behaviour of a metal during solidification using a mesh generation technique of the heterogeneous semi-solid material for a finite element analysis at the microscopic level. This task is done on a two-dimensional (2D) domain in which the granular structure of the solid phase is generated surrounded by an intergranular and interdendritc liquid phase. Some basic solid grains are first constructed and projected in the 2D domain with random orientations and scale factors. Depending on their orientation, the basic grains are combined to produce larger grains or separated by a liquid film. Different basic grain shapes can produce different granular structures of the mushy zone. As a result, using this automatic grain generation procedure, we can investigate the effect of grain shapes and sizes on the thermo-mechanical behaviour of the semi-solid material. The granular models are automatically converted to the finite element meshes. The solid grains and the liquid phase are meshed properly using quadrilateral elements. This method has been used to simulate the microstructure of a binary aluminium–copper alloy (Al–5.8 wt% Cu) when the fraction solid is 0.92. Using the finite element method and the Mie–Grüneisen equation of state for the liquid phase, the transient mechanical behaviour of the mushy zone under tensile loading has been investigated. The stress distribution and the bridges, which are formed during the tensile loading, have been detected. (paper)

  16. Measurements on cation exchange capacity of bentonite in the long-term test of buffer material (LOT)

    International Nuclear Information System (INIS)

    Muurinen, A.

    2011-01-01

    Determination of cation exchange capacity (CEC) of bentonite in the LOT experiment was the topic of this study. The measurements were performed using the complex of copper(II) ion with trietylenetetramine [Cu(trien)] 2+ as the index cation. Testing of the determination method suggested that (i) drying and wetting of the bentonite, and (ii) exchange time affect the obtained result. The real CEC measurements were carried out with the bentonite samples taken from the A2 parcel of the LOT experiment. The CEC values of the LOT samples were compared with those of the reference samples taken from the same bentonite batch before the compaction of the blocks for the experiment. The conclusions drawn have been made on the basis of the results determined with the wet bentonite samples using the direct exchange of two weeks with 0.01 M [Cu(trien)] 2+ solution because this method gave the most complete cation exchange in the CEC measurements. The differences between the samples taken from different places of the A2 parcel were quite small and close to the accuracy of the method. However, it seems that the CEC values of the field experiment are somewhat higher than the CEC of the reference samples and the values of the hot area are higher than those obtained from the low temperature area. It is also obvious that the variation of CEC increases with increasing temperature. (orig.)

  17. Influence of particle shape on the microstructure evolution and the mechanical properties of granular materials

    Science.gov (United States)

    Tian, Jianqiu; Liu, Enlong; Jiang, Lian; Jiang, Xiaoqiong; Sun, Yi; Xu, Ran

    2018-06-01

    In order to study the influence of particle shape on the microstructure evolution and the mechanical properties of granular materials, a two-dimensional DEM analysis of samples with three particle shapes, including circular particles, triangular particles, and elongated particles, is proposed here to simulate the direct shear tests of coarse-grained soils. For the numerical test results, analyses are conducted in terms of particle rotations, fabric evolution, and average path length evolution. A modified Rowe's stress-dilatancy equation is also proposed and successfully fitted onto simulation data.

  18. Combined full field stress and strain measurement methods for granular materials

    Directory of Open Access Journals (Sweden)

    Broere W.

    2010-06-01

    Full Text Available The current paper re-introduces the photoelastic measurement method in experimental geomechanics. A full-field phase stepping polariscope suitable for geomechanical model tests has been developed. Additional constraints on the measurement and mechanical setup arising from geomechanical test conditions are outlined as well as the opportunity to measure the displacement fields in the sample with digital image correlation. The capability of the current setup in retrieving the stress and strain field in a granular material is demonstrated.

  19. Hydraulic properties of domestic bentonite-sand mixture as a backfill material in the high-level waste repository

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Won Jin; Lee, Jae Owan; Kang, Chul Hyung [Korea Atomic Energy Research Institute, Taejeon (Korea)

    2000-02-01

    This study is intended to investigate the effect of dry density and sand content on hydraulic conductivities of bentonite-sand mixtures. The hydraulic conductivities of bentonite-sand mixtures with dry densities of 1.6 and 1.8 Mg/m{sup 3} are lower than 10{sup -11} m/s if their sand contents are less than 70 wt%. However at the sand content of 90 wt%, the hydraulic conductivities increase sharply. In the case of sand contents not exceeding 70 wt%, the logarithm of the hydraulic conductivity of bentonite-sand mixture increase linearly with increasing sand content. The hydraulic conductivity of the mixture can be explained using 'effective clay dry density' concept. 16 refs., 21 figs., 5 tabs. (Author)

  20. Developing a Magnetic Resonance Imaging measurement of the forces within 3D granular materials under external loads

    Science.gov (United States)

    Elrington, Stefan; Bertrand, Thibault; Frey, Merideth; Shattuck, Mark; O'Hern, Corey; Barrett, Sean

    2014-03-01

    Granular materials are comprised of an ensemble of discrete macroscopic grains that interact with each other via highly dissipative forces. These materials are ubiquitous in our everyday life ranging in scale from the granular media that forms the Earth's crust to that used in agricultural and pharmaceutical industries. Granular materials exhibit complex behaviors that are poorly understood and cannot be easily described by statistical mechanics. Under external loads individual grains are jammed into place by a network of force chains. These networks have been imaged in quasi two-dimensional and on the outer surface of three-dimensional granular materials. Our goal is to use magnetic resonance imaging (MRI) to detect contact forces deep within three-dimensional granular materials, using hydrogen-1 relaxation times as a reporter for changes in local stress and strain. To this end, we use a novel pulse sequence to narrow the line width of hydrogen-1 in rubber. Here we present our progress to date, and prospects for future improvements.

  1. Elaboration of building materials from industrial waste from solid granular diatomaceous earth; Elaboracion de material de construccion a partir de residuos industriales solidos granulares procedentes de tierras diatomaceas

    Energy Technology Data Exchange (ETDEWEB)

    Del Angel S, A.

    2015-07-01

    In this work the initial characterization of granular solid industrial waste from diatomaceous earth was carried out using techniques of Scanning Electron Microscopy and X-ray Diffraction. In a second stage leaching of the material was undertaken to the US Patent Number 5, 376,000 and 5, 356,601 obtaining the samples M1-S ph 2, M1-L ph, M1-S ph 10 and M1-L ph 10. In the third stage a new characterization of the samples obtained with the techniques of Scanning Electron Microscopy, X-ray Diffraction and Atomic Absorption Spectrometry was performed, the latter in order to determine the efficiency percentage of the leaching process. In the fourth stage the specimens for performing mechanical, physical and chemical tests were manufactured, using molds as PVC pipes of 1 inch in diameter and 2 inches in length, with a composition of 50% of diatomaceous earth and 50% of cement produced in each. Finally, in the fifth stage mechanical testing (compression resistance), physical (moisture absorption rate) and chemical (composition and structure of the material) are performed. In the last stage, when conducting mechanical testing with the test specimens, the presence of bubbles enclosed in each obtaining erroneous results noted, so it was necessary to develop the specimens again, obtaining in this occasion concentrations of 20:80, 40:60, 60:40 and 80:20 of diatomaceous earth with the cement. These results were analyzed to determine if the used material is suitable for the production of building materials such as bricks or partitions, being demonstrated by the tests carried out if they are eligible. (Author)

  2. The bentonite industry in North America

    International Nuclear Information System (INIS)

    Dixon, D.A.; Hnatiw, D.S.J.; Walker, B.T.

    1992-11-01

    The Canadian Nuclear Fuel Waste Management Program is studying a concept for the disposal of nuclear fuel waste at a depth of 500 to 1000 m below the surface in stable crystalline rock of the Canadian Shield. The waste containers would be surrounded by a clay-based buffer material, composed of equal proportions of bentonite clay and silica sand. In the reference disposal concept, some 1.9 x 10 5 Mg of used fuel would be emplaced. This would require 2.5 x 10 6 Mg of bentonite. A review of the bentonite industry in North America was carried out to establish the availability of sufficient high-quality material. There are proven reserves of sodium bentonite clay in excess of 1.5 x 10 8 Mg, and vast supplies are known to exist but not yet proven. The Canadian conceptual disposal vault would require 6 x 10 4 Mg of sodium bentonite each year for 40 years. The bentonite industry of North America has an installed annual production capacity of 2 x 10 7 Mg. A disposal vault would therefore require approximately 2% of the industry capacity. A number of commercial products have been screened for potential suitability for use as a component of the buffer. Ten currently marketed bentonite products have been identified as meeting the initial quality standards for the buffer, and two non-commercial bentonites have been identified as having the potential for use in a disposal vault. (Author) (14 figs., 7 tabs., 18 refs.)

  3. DEM Simulation of Biaxial Compression Experiments of Inherently Anisotropic Granular Materials and the Boundary Effects

    Directory of Open Access Journals (Sweden)

    Zhao-Xia Tong

    2013-01-01

    Full Text Available The reliability of discrete element method (DEM numerical simulations is significantly dependent on the particle-scale parameters and boundary conditions. To verify the DEM models, two series of biaxial compression tests on ellipse-shaped steel rods are used. The comparisons on the stress-strain relationship, strength, and deformation pattern of experiments and simulations indicate that the DEM models are able to capture the key macro- and micromechanical behavior of inherently anisotropic granular materials with high fidelity. By using the validated DEM models, the boundary effects on the macrodeformation, strain localization, and nonuniformity of stress distribution inside the specimens are investigated using two rigid boundaries and one flexible boundary. The results demonstrate that the boundary condition plays a significant role on the stress-strain relationship and strength of granular materials with inherent fabric anisotropy if the stresses are calculated by the force applied on the wall. However, the responses of the particle assembly measured inside the specimens are almost the same with little influence from the boundary conditions. The peak friction angle obtained from the compression tests with flexible boundary represents the real friction angle of particle assembly. Due to the weak lateral constraints, the degree of stress nonuniformity under flexible boundary is higher than that under rigid boundary.

  4. Computational domain discretization in numerical analysis of flow within granular materials

    Science.gov (United States)

    Sosnowski, Marcin

    2018-06-01

    The discretization of computational domain is a crucial step in Computational Fluid Dynamics (CFD) because it influences not only the numerical stability of the analysed model but also the agreement of obtained results and real data. Modelling flow in packed beds of granular materials is a very challenging task in terms of discretization due to the existence of narrow spaces between spherical granules contacting tangentially in a single point. Standard approach to this issue results in a low quality mesh and unreliable results in consequence. Therefore the common method is to reduce the diameter of the modelled granules in order to eliminate the single-point contact between the individual granules. The drawback of such method is the adulteration of flow and contact heat resistance among others. Therefore an innovative method is proposed in the paper: single-point contact is extended to a cylinder-shaped volume contact. Such approach eliminates the low quality mesh elements and simultaneously introduces only slight distortion to the flow as well as contact heat transfer. The performed analysis of numerous test cases prove the great potential of the proposed method of meshing the packed beds of granular materials.

  5. Relationship between electrical conductivity anisotropy and fabric anisotropy in granular materials during drained triaxial compressive tests: a numerical approach

    Science.gov (United States)

    Niu, Qifei; Revil, André; Li, Zhaofeng; Wang, Yu-Hsing

    2017-07-01

    The anisotropy of granular media and its evolution during shearing are important aspects required in developing physics-based constitutive models in Earth sciences. The development of relationships between geoelectrical properties and the deformation of porous media has applications to the monitoring of faulting and landslides. However, such relationships are still poorly understood. In this study, we first investigate the definition of the electrical conductivity anisotropy tensor of granular materials in presence of surface conductivity of the grains. Fabric anisotropy is related to the components of the fabric tensor. We define an electrical anisotropy factor based on the Archie's exponent second-order symmetric tensor m of granular materials. We use numerical simulations to confirm a relationship between the evolution of electrical and fabric anisotropy factors during shearing. To realize the simulations, we build a virtual laboratory in which we can easily perform synthetic experiments. We first simulate drained compressive triaxial tests of loose and dense granular materials (porosity 0.45 and 0.38, respectively) using the discrete element method. Then, the electrical conductivity tensor of a set of deformed synthetic samples is computed using the finite-difference method. The numerical results show that shear strains are responsible for a measurable anisotropy in the bulk conductivity of granular media. The observed electrical anisotropy response, during shearing, is distinct for dense and loose synthetic samples. Electrical and fabric anisotropy factors exhibit however a unique linear correlation, regardless of the shear strain and the initial state (porosity) of the synthetic samples. The practical implication of this finding confirms the usefulness of the electrical conductivity method in studying the fabric tensor of granular media. This result opens the door in using time-lapse electrical resistivity to study non-intrusively the evolution of anisotropy

  6. Shear dilatancy and acoustic emission in dry and saturated granular materials

    Science.gov (United States)

    Brodsky, E. E.; Siman-Tov, S.

    2017-12-01

    Shearing of granular materials plays a strong role in naturally sheared systems as landslides and faults. Many works on granular flows have concentrated on dry materials, but relatively little work has been done on water saturated sands. Here we experimentally investigate dry versus saturated quartz-rich sand to understand the effect of the fluid medium on the rheology and acoustic waves emission of the sheared sand. The sand was sheared in a rotary shear rheometer under applied constant normal stress boundary at low (100 µm/s) to high (1 m/s) velocities. Mechanical, acoustic data and deformation were continuously recorded and imaged. For dry and water saturated experiments the granular volume remains constant for low shear velocities ( 10-3 m/s) and increases during shearing at higher velocities ( 1 m/s). Continuous imaging of the sheared sand show that the steady state shear band thickness is thicker during the high velocity steps. No significant change observed in the shear band thickness between dry and water saturated experiments. In contrast, the amount of dilation during water saturated experiments is about half the value measured for dry material. The measured decrease cannot be explained by shear band thickness change as such is not exist. However, the reduced dilation is supported by our acoustic measurements. In general, the event rate and acoustic event amplitudes increase with shear velocity. While isolated events are clearly detected during low velocities at higher the events overlap, resulting in a noisy signal. Although detection is better for saturated experiments, during the high velocity steps the acoustic energy measured from the signal is lower compared to that recorded for dry experiments. We suggest that the presence of fluid suppresses grain motion and particles impacts leading to mild increase in the internal pressure and therefore for the reduced dilation. In addition, the viscosity of fluids may influence the internal pressure via

  7. Resilient modulus for unbound granular materials and subgrade soils in Egypt

    Directory of Open Access Journals (Sweden)

    Mousa Rabah

    2017-01-01

    Full Text Available Mechanistic Empirical (ME pavement design methods started to gain attention especially the last couple of years in Egypt and the Middle East. One of the challenges facing the spread of these methods in Egypt is lack of advanced properties of local soil and asphalt, which are needed as input data in ME design. Resilient modulus (Mr for example is an important engineering property that expresses the elastic behavior of soil/unbound granular materials (UGMs under cyclic traffic loading for ME design. In order to overcome the scarcity of the resilient modulus data for soil/UGMs in Egypt, a comprehensive laboratory testing program was conducted to measure resilient modulus of typical UGMs and subgrade soils typically used in pavement construction in Egypt. The factors that affect the resilient modulus of soil/UGMs were reviewed, studied and discussed. Finally, the prediction accuracy of the most well-known Mr Prediction models for the locally investigated materials was investigated.

  8. Bentonite erosion. Laboratory studies

    Energy Technology Data Exchange (ETDEWEB)

    Jansson, Mats (Div. of Nuclear Chemistry, Royal Inst. of Technology, Stockholm (Sweden), School of Chemical Science and Engineering)

    2009-11-15

    This report covers the laboratory studies that have been performed at Nuclear Chemistry, KTH in the project 'Bentonite Erosion'. Many of the experiments in this report were performed to support the work of the modelling group and were often relatively simple. One of the experiment series was performed to see the impact of gravity and concentration of mono- and di-valent cations. A clay suspension was prepared in a test tube. A net was placed in contact with the suspension, the test tube was filled with solutions of different concentrations and the system was left overnight to settle. The tube was then turned upside down and the behaviour was visually observed. Either the clay suspension fell through the net or stayed on top. By using this method surprisingly sharp determinations of the Critical Coagulation (Flocculation) Concentration (CCC/CFC) could be made. The CCC/CFC of Ca2+ was for sodium montmorillonite determined to be between 1 and 2 mM. An artificial fracture was manufactured in order to simulate the real case scenario. The set-up was two Plexiglas slabs separated by 1 mm thick spacers with a bentonite container at one side of the fracture. Water was pumped with a very low flow rate perpendicular to bentonite container and the water exiting the fracture was sampled and analyzed for colloid content. The bentonite used was treated in different ways. In the first experiment a relatively montmorillonite rich clay was used while in the second bentonite where only the readily soluble minerals had been removed was used. Since Plexiglas was used it was possible to visually observe the bentonite dispersing into the fracture. After the compacted bentonite (1,000 kg/m3) had been water saturated the clay had expanded some 12 mm out into the fracture. As the experiment progressed the clay expanded more out into the fracture and seemed to fractionate in two different phases with less material in the outmost phase. A dark rim which was later analyzed to contain

  9. Flow and Jamming of Granular Materials in a Two-dimensional Hopper

    Science.gov (United States)

    Tang, Junyao

    Flow in a hopper is both a fertile testing ground for understanding fundamental granular flow rheology and industrially highly relevant. Despite increasing research efforts in this area, a comprehensive physical theory is still lacking for both jamming and flow of granular materials in a hopper. In this work, I have designed a two dimensional (2D) hopper experiment using photoelastic particles (particles' shape: disk or ellipse), with the goal to build a bridge between macroscopic phenomenon of hopper flow and microscopic particle-scale dynamics. Through synchronized data of particle tracking and stress distributions in particles, I have shown differences between my data of the time-averaged velocity/stress profile of 2D hopper flow with previous theoretical predictions. I have also demonstrated the importance of a mechanical stable arch near the opening on controlling hopper flow rheology and suggested a heuristic phase diagram for the hopper flow/jamming transition. Another part of this thesis work is focused on studying the impact of particle shape of particles on hopper flow. By comparing particle-tracking and photoelastic data for ellipses and disks at the appropriate length scale, I have demonstrated an important role for the rotational freedom of elliptical particles in controlling flow rheology through particle tracking and stress analysis. This work has been supported by International Fine Particle Research Institute (IFPRI) .

  10. Does modifying the particle size distribution of a granular material (i.e., material scalping alters its shear strength?

    Directory of Open Access Journals (Sweden)

    Azéma Emilien

    2017-01-01

    Full Text Available By means of two dimensional contact dynamics simulations, we analyzed the effect of the particle size distribution (PSD on the shear strength of granular materials composed of un-breakable disks. We modelled PSDs with a normalized beta function, which allows for building S-shaped gradation curves, such as those that typically occur in soils. We systematically controlled and varied the size span and the shape of the PSD, and found that the shear strength is independent both characteristics. This implies that PSD modification procedures such as material scalping (i.e., removing the smallest and/or largest particles in the sample should not affect significantly the shear strength of the material composed of unbreakable discs. In order to explore the origins of the invariance of the shear strength with PSD, we analyzed the connectivity, force transmission, and friction mobilization in terms of anisotropies, finding that the constant shear strength is due to a subtle compensation of anisotropies.

  11. Granular Materials and the Risks They Pose for Success on the Moon and Mars

    Science.gov (United States)

    Wilkinson, R. Allen; Behringer, Robert P.; Jenkins, James T.; Louge, Michel Y.

    2005-02-01

    Working with soil, sand, powders, ores, cement and sintered bricks, excavating, grading construction sites, driving off-road, transporting granules in chutes and pipes, sifting gravel, separating solids from gases, and using hoppers are so routine that it seems straightforward to do it on the Moon and Mars as we do it on Earth. This paper brings to the fore how little these processes are understood and the millennia-long trial-and-error practices that lead to today's massive over-design, high failure rate, and extensive incremental scaling up of industrial processes because of the inadequate predictive tools for design. We present a number of pragmatic scenarios where granular materials play a role, the risks involved, and what understanding is needed to greatly reduce the risks.

  12. A thermomechanical constitutive model for cemented granular materials with quantifiable internal variables. Part I-Theory

    Science.gov (United States)

    Tengattini, Alessandro; Das, Arghya; Nguyen, Giang D.; Viggiani, Gioacchino; Hall, Stephen A.; Einav, Itai

    2014-10-01

    This is the first of two papers introducing a novel thermomechanical continuum constitutive model for cemented granular materials. Here, we establish the theoretical foundations of the model, and highlight its novelties. At the limit of no cement, the model is fully consistent with the original Breakage Mechanics model. An essential ingredient of the model is the use of measurable and micro-mechanics based internal variables, describing the evolution of the dominant inelastic processes. This imposes a link between the macroscopic mechanical behavior and the statistically averaged evolution of the microstructure. As a consequence this model requires only a few physically identifiable parameters, including those of the original breakage model and new ones describing the cement: its volume fraction, its critical damage energy and bulk stiffness, and the cohesion.

  13. Numerical Simulation on Dense Packing of Granular Materials by Container Oscillation

    Directory of Open Access Journals (Sweden)

    Jun Liu

    2013-01-01

    Full Text Available The packing of granular materials is a basic and important problem in geomechanics. An approach, which generates dense packing of spheres confined in cylindrical and cuboidal containers in three steps, is introduced in this work. A loose packing structure is first generated by means of a reference lattice method. Then a dense packing structure is obtained in a container by simulating dropping of particles under gravitational forces. Furthermore, a scheme that makes the bottom boundary fluctuate up and down was applied to obtain more denser packing. The discrete element method (DEM was employed to simulate the interactions between particle-particle and particle-boundary during the particles' motions. Finally, two cases were presented to indicate the validity of the method proposed in this work.

  14. Leaching behaviour of municipal solid waste incineration bottom ash: From granular material to monolithic concrete.

    Science.gov (United States)

    Sorlini, Sabrina; Collivignarelli, Maria Cristina; Abbà, Alessandro

    2017-09-01

    The aim of this work was to assess the leaching behaviour of the bottom ash derived from municipal solid waste incineration (MSWI) used in concrete production. In particular, the release of pollutants was evaluated by the application of different leaching tests, both on granular materials and monolithic samples (concrete mixtures cast with bottom ash). The results confirmed that, according to Italian regulations, unwashed bottom ashes present critical issues for the use as alternative aggregates in the construction sector due to the excessive release of pollutants; instead, the leachate from washed bottom ashes was similar to natural aggregates. The concentration of pollutants in the leachate from concrete mixtures was lower than regulation limits for reuse. The crushing process significantly influenced the release of pollutants: this behaviour was due both to the increase in surface area and the release of contaminants from cement. Moreover, the increase in contact time (up to 64 days) involved more heavy metals to be released.

  15. Shear test results for cohesion and friction coefficients for different granular materials : Scaling implications for their usage in analogue modelling

    NARCIS (Netherlands)

    Schellart, W. P.

    2000-01-01

    Laboratory tests have been carried out on dry granular materials such as quartz sand, glass microspheres and sugar with different grain size, rounding and sphericity. The measurements have been made with a simple shear test machine for different values of normal stress (~ 50-900 Pa). Shear stress

  16. Advances in the simulation and automated measurement of well-sorted granular material: 2. Direct measures of particle properties

    Science.gov (United States)

    Buscombe, D.; Rubin, D. M.

    2012-06-01

    In this, the second of a pair of papers on the structure of well-sorted natural granular material (sediment), new methods are described for automated measurements from images of sediment, of: 1) particle-size standard deviation (arithmetic sorting) with and without apparent void fraction; and 2) mean particle size in material with void fraction. A variety of simulations of granular material are used for testing purposes, in addition to images of natural sediment. Simulations are also used to establish that the effects on automated particle sizing of grains visible through the interstices of the grains at the very surface of a granular material continue to a depth of approximately 4 grain diameters and that this is independent of mean particle size. Ensemble root-mean squared error between observed and estimated arithmetic sorting coefficients for 262 images of natural silts, sands and gravels (drawn from 8 populations) is 31%, which reduces to 27% if adjusted for bias (slope correction between observed and estimated values). These methods allow non-intrusive and fully automated measurements of surfaces of unconsolidated granular material. With no tunable parameters or empirically derived coefficients, they should be broadly universal in appropriate applications. However, empirical corrections may need to be applied for the most accurate results. Finally, analytical formulas are derived for the one-step pore-particle transition probability matrix, estimated from the image's autocorrelogram, from which void fraction of a section of granular material can be estimated directly. This model gives excellent predictions of bulk void fraction yet imperfect predictions of pore-particle transitions.

  17. Mechanical strength model for plastic bonded granular materials at high strain rates and large strains

    International Nuclear Information System (INIS)

    Browning, R.V.; Scammon, R.J.

    1998-01-01

    Modeling impact events on systems containing plastic bonded explosive materials requires accurate models for stress evolution at high strain rates out to large strains. For example, in the Steven test geometry reactions occur after strains of 0.5 or more are reached for PBX-9501. The morphology of this class of materials and properties of the constituents are briefly described. We then review the viscoelastic behavior observed at small strains for this class of material, and evaluate large strain models used for granular materials such as cap models. Dilatation under shearing deformations of the PBX is experimentally observed and is one of the key features modeled in cap style plasticity theories, together with bulk plastic flow at high pressures. We propose a model that combines viscoelastic behavior at small strains but adds intergranular stresses at larger strains. A procedure using numerical simulations and comparisons with results from flyer plate tests and low rate uniaxial stress tests is used to develop a rough set of constants for PBX-9501. Comparisons with the high rate flyer plate tests demonstrate that the observed characteristic behavior is captured by this viscoelastic based model. copyright 1998 American Institute of Physics

  18. Mechanical and Structural Behavior of Granular Material Packed Beds for Space Life Support System Applications

    Science.gov (United States)

    Malla, Ramesh B.; Anandakumar, Ganesh

    2005-01-01

    Long-term human mission to space, such as living in International Space Station (ISS), Lunar, and Martian bases, and travel to Mars, must m ake use of Advanced Life Support Systems (ALSS) to generate and recycle critical life supporting elements like oxygen and water. Oxygen Gen eration Assembly (OGA) and Water Processor Assembly (WPA), critical c omponents of ALSS, make use of series of granular material packed beds for generation and recycling of oxygen and water. Several granular m aterials can be used for generation, recycling, processing and recovery of oxygen and water. For example, they may include soft bed media, e.g. ion exchange resins for oxygen generation assembly and hard bed media such as, activated alumina, magchem (Magnesium oxide) and activa ted carbon to remove organic species like ethanol, methanol, and urea from wastewater in Water recovery/processing assembly. These beds are generally packed using a plate-spring mechanism to provide sufficien t compaction to the bed media throughout the course of operation. This paper presents results from an experimental study of a full-scale, 3 8.1 cm (15 inches) long and 3.7 cm (1.44 inches) diameter. activated alumina bed enclosed in a cylinder determining its force-displacement behavior, friction mobilizing force, and axial normal stress distribu tion under various axially applied loads and at different levels of packing. It is observed that force-displacement behavior is non-linear for low compaction level and becomes linear with increase in compaction of the bed media. Axial normal stress distribution along the length of the bed media decreased non-linearly with increase in depth from the loading end of the granular media. This paper also presents experimental results on the amount of particulates generated corresponding to various compaction levels. Particulates generated from each of the tests were measured using standard US sieves. It was found that the p articulates and the overall displacement of

  19. Rapid injection of particles and gas into non-fluidized granular material, and some volcanological implications

    Science.gov (United States)

    Ross, Pierre-Simon; White, James D. L.; Zimanowski, Bernd; Büttner, Ralf

    2008-10-01

    In diatremes and other volcanic vents, steep bodies of volcaniclastic material having differing properties (particle size distribution, proportion of lithic fragments, etc.) from those of the surrounding vent-filling volcaniclastic material are often found. It has been proposed that cylindrical or cone-shaped bodies result from the passage of “debris jets” generated after phreatomagmatic explosions or other discrete subterranean bursts. To learn more about such phenomena, we model experimentally the injection of gas-particulate dispersions through other particles. Analogue materials (glass beads or sand) and a finite amount of compressed air are used in the laboratory. The gas is made available by rapidly opening a valve—therefore the injection of gas and coloured particles into a granular host is a brief (non-erupting injections produce cylindrical bodies of coloured beads whereas erupting runs produce flaring upward or conical deposits. Changing the particle size of the host glass beads does not have a large effect under the size range investigated (100 200 to 300 400 μm). Doubling the host thickness (injection depth) requires a doubling of the initial gas pressure to produce similar phenomena. Such injections—whether erupting or wholly subterranean—provide a compelling explanation for the origin and characteristics of multiple cross-cutting bodies that have been documented for diatreme and other vent deposits.

  20. Granular superconductor in a honeycomb lattice as a realization of bosonic Dirac material

    Science.gov (United States)

    Banerjee, S.; Fransson, J.; Black-Schaffer, A. M.; Ågren, H.; Balatsky, A. V.

    2016-04-01

    We examine the low-energy effective theory of phase oscillations in a two-dimensional granular superconducting sheet where the grains are arranged in a honeycomb lattice structure. Using the example of graphene, we present evidence for the engineered Dirac nodes in the bosonic excitations: the spectra of the collective bosonic modes cross at the K and K' points in the Brillouin zone and form Dirac nodes. We show how two different types of collective phase oscillations are obtained and that they are analogous to the Leggett and the Bogoliubov-Anderson-Gorkov modes in a two-band superconductor. We show that the Dirac node is preserved in the presence of an intergrain interaction, despite induced changes of the qualitative features of the two collective modes. Finally, breaking the sublattice symmetry by choosing different on-site potentials for the two sublattices leads to a gap opening near the Dirac node, in analogy with fermionic Dirac materials. The Dirac node dispersion of bosonic excitations is thus expanding the discussion of the conventional Dirac cone excitations to the case of bosons. We call this case as a representative of bosonic Dirac materials (BDM), similar to the case of Fermionic Dirac materials extensively discussed in the literature.

  1. Stress distribution retrieval in granular materials: A multi-scale model and digital image correlation measurements

    Science.gov (United States)

    Bruno, Luigi; Decuzzi, Paolo; Gentile, Francesco

    2016-01-01

    The promise of nanotechnology lies in the possibility of engineering matter on the nanoscale and creating technological interfaces that, because of their small scales, may directly interact with biological objects, creating new strategies for the treatment of pathologies that are otherwise beyond the reach of conventional medicine. Nanotechnology is inherently a multiscale, multiphenomena challenge. Fundamental understanding and highly accurate predictive methods are critical to successful manufacturing of nanostructured materials, bio/mechanical devices and systems. In biomedical engineering, and in the mechanical analysis of biological tissues, classical continuum approaches are routinely utilized, even if these disregard the discrete nature of tissues, that are an interpenetrating network of a matrix (the extra cellular matrix, ECM) and a generally large but finite number of cells with a size falling in the micrometer range. Here, we introduce a nano-mechanical theory that accounts for the-non continuum nature of bio systems and other discrete systems. This discrete field theory, doublet mechanics (DM), is a technique to model the mechanical behavior of materials over multiple scales, ranging from some millimeters down to few nanometers. In the paper, we use this theory to predict the response of a granular material to an external applied load. Such a representation is extremely attractive in modeling biological tissues which may be considered as a spatial set of a large number of particulate (cells) dispersed in an extracellular matrix. Possibly more important of this, using digital image correlation (DIC) optical methods, we provide an experimental verification of the model.

  2. Study of an athermal quasi static plastic deformation in a 2D granular material

    Science.gov (United States)

    Zhang, Jie

    2017-11-01

    In crystalline materials, the plasticity has been well understood in terms of dynamics of dislocation, i.e. flow defects in the crystals where the flow defects can be directly visualized under a microscope. In a contrast, the plasticity in amorphous materials, i.e. glass, is still poorly understood due to the disordered nature of the materials. In this talk, I will discuss the recent results we have obtained in our ongoing research of the plasticity of a 2D glass in the athermal quasi static limit where the 2D glass is made of bi-disperse granular disks with very low friction. Starting from a densely packed homogeneous and isotropic initial state, we apply pure shear deformation to the system. For a sufficiently small strain, the response of the system is linear and elastic like; when the strain is large enough, the plasticity of the system gradually develops and eventually the shear bands are fully developed. In this study, we are particularly interested in how to relate the local plastic deformation to the macroscopic response of the system and also in the development of the shear bands.

  3. Rheological Behavior of Bentonite-Polyester Dispersions

    Science.gov (United States)

    Abu-Jdayil, Basim; Al-Omari, Salah Addin

    2013-07-01

    The rheological behavior of a bentonite clay dispersed in unsaturated polyester was investigated. The effects of the solid content and particle size on the steady and transient rheological properties of the dispersions were studied. In addition, two types of bentonite with different Na+/Ca+2 ratio were used in this study. The Herschel-Bulkley and the Weltman models were used to describe the apparent viscosity of the bentonite-polyester composite in relation to the shear rate and shearing time. The bentonite-polyester dispersions were found to exhibit both Newtonian and non-Newtonian behavior. The transition from a Newtonian to a Bingham plastic and then to a shear-thinning material with a yield stress was found to depend on the solid concentration, the particle size, and the type of bentonite. At a low solid content, the apparent viscosity of the bentonite dispersion increased linearly with solid concentration. But a dramatic increase in the apparent viscosity beyond a solid content of 20 wt.% was observed. On the other hand, a thixotropic behavior was detected in bentonite-polyester dispersions with a high solid content and a low particle size. However, this behavior was more pronounced in dispersions with a high Na+/Ca+2 ratio.

  4. A new methodology to simulate subglacial deformation of water saturated granular material

    DEFF Research Database (Denmark)

    Damsgaard, Anders; Egholm, David Lundbek; Piotrowski, Jan A.

    2015-01-01

    The dynamics of glaciers are to a large degree governed by processes operating at the ice-bed interface, and one of the primary mechanisms of glacier flow over soft unconsolidated sediments is subglacial deformation. However, it has proven difficult to constrain the mechanical response of subglac......The dynamics of glaciers are to a large degree governed by processes operating at the ice-bed interface, and one of the primary mechanisms of glacier flow over soft unconsolidated sediments is subglacial deformation. However, it has proven difficult to constrain the mechanical response...... or weakening components, depending on the rate of deformation, the material state, clay mineral content, and the hydrological properties of the material. The influence of the fluid phase is negligible when relatively permeable sediment is deformed. However, by reducing the local permeability, fast deformation...... can cause variations in the pore-fluid pressure. The pressure variations weaken or strengthen the granular phase, and in turn influence the distribution of shear strain with depth. In permeable sediments the strain distribution is governed by the grain-size distribution and effective normal stress...

  5. Attachment and Detachment Behavior of Human Adenovirus and Surrogates in Fine Granular Limestone Aquifer Material.

    Science.gov (United States)

    Stevenson, Margaret E; Sommer, Regina; Lindner, Gerhard; Farnleitner, Andreas H; Toze, Simon; Kirschner, Alexander K T; Blaschke, Alfred P; Sidhu, Jatinder P S

    2015-09-01

    The transport of human adenovirus, nanoparticles, and PRD1 and MS2 bacteriophages was tested in fine granular limestone aquifer material taken from a borehole at a managed aquifer recharge site in Adelaide, South Australia. Comparison of transport and removal of virus surrogates with the pathogenic virus is necessary to understand the differences between the virus and surrogate. Because experiments using pathogenic viruses cannot be done in the field, laboratory tests using flow-through soil columns were used. Results show that PRD1 is the most appropriate surrogate for adenovirus in an aquifer dominated by calcite material but not under high ionic strength or high pH conditions. It was also found that straining due to size and the charge of the colloid were not dominant removal mechanisms in this system. Implications of this study indicate that a certain surrogate may not represent a specific pathogen solely based on similar size, morphology, and/or surface charge. Moreover, if a particular surrogate is representative of a pathogen in one aquifer system, it may not be the most appropriate surrogate in another porous media system. This was apparent in the inferior performance of MS2 as a surrogate, which is commonly used in virus transport studies. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

  6. Influence of granular material characteristics in the behaviour of “Bouregreg Valley” soft ground improved with stone columns

    Directory of Open Access Journals (Sweden)

    Nehab Noura

    2018-01-01

    Full Text Available The use of finite element analysis has become widespread in geotechnical practice as means of optimizing engineering tasks; it can be easily applied to the treated areas by stone columns, which are a method of improving the soil having low geotechnical properties and likely to deform significantly under load action, by incorporating granular material (commonly called ballast compacted by remounting passes, so they act mainly as inclusions with a higher stiffness, shear strength than the natural soil. Moreover the stone columns are highly permeable and act as vertical drains facilitating consolidation of the soft soil improving the performance of the foundation. However the characteristics of this granular material influence the behavior of soft soils treated by the stone columns technique, especially: the friction angle, the cohesion, the modular ratio and the constitutive model. The choice of the constitutive model depends on many factors but, in general, it is related to the type of analysis that we intend to perform. Numerical modeling must consider the diversity of the materials nature, the complex geometry of structures-land and the behavior of materials generally nonlinear (permanent deformation. It is a simple and effective alternative to approach the real behavior of soils reinforced by stone columns and the influence of materials characteristics, it allows settlement analysis, lateral deformation, vertical and horizontal stresses in order to understand the behavior of columns and soil. It also has the advantage of integrating the settlements of the underlying layers. This paper aims to study the mechanisms of functioning and interactions of stone columns with the surrounding ground, and vis-à-vis the various parameters characterizing the granular material "ballast" and the surrounding soil, which influence the behavior of the improved soil, The paper presents, in the first part, soil conditions and the parameters associated with

  7. Elaboration of building materials from industrial waste from solid granular diatomaceous earth

    International Nuclear Information System (INIS)

    Del Angel S, A.

    2015-01-01

    In this work the initial characterization of granular solid industrial waste from diatomaceous earth was carried out using techniques of Scanning Electron Microscopy and X-ray Diffraction. In a second stage leaching of the material was undertaken to the US Patent Number 5, 376,000 and 5, 356,601 obtaining the samples M1-S ph 2, M1-L ph, M1-S ph 10 and M1-L ph 10. In the third stage a new characterization of the samples obtained with the techniques of Scanning Electron Microscopy, X-ray Diffraction and Atomic Absorption Spectrometry was performed, the latter in order to determine the efficiency percentage of the leaching process. In the fourth stage the specimens for performing mechanical, physical and chemical tests were manufactured, using molds as PVC pipes of 1 inch in diameter and 2 inches in length, with a composition of 50% of diatomaceous earth and 50% of cement produced in each. Finally, in the fifth stage mechanical testing (compression resistance), physical (moisture absorption rate) and chemical (composition and structure of the material) are performed. In the last stage, when conducting mechanical testing with the test specimens, the presence of bubbles enclosed in each obtaining erroneous results noted, so it was necessary to develop the specimens again, obtaining in this occasion concentrations of 20:80, 40:60, 60:40 and 80:20 of diatomaceous earth with the cement. These results were analyzed to determine if the used material is suitable for the production of building materials such as bricks or partitions, being demonstrated by the tests carried out if they are eligible. (Author)

  8. Study on the basic property of Gaomiaozi bentonite, inner mongolia

    International Nuclear Information System (INIS)

    Liu Yuemiao; Xu Guoqing; Liu Shufen; Chen Zhangru

    2001-01-01

    Buffer/backfill material layer is one of important engineered barriers in the HLW geological repository. The geologic setting of Gaomiaozi bentonite deposit is introduced, and the mineral composition, physical and chemical property, basic geotechnical property, swelling property and permeability of highly compacted bentonite of main ore bed has been studied. The study results show that montmorillonite content of Gaomiaozi bentonite is relatively high, physical and chemical property, geotechnical property and impermeability are good. So Gaomiaozi bentonite deposit could be regarded as supply base of buffer/backfill material for HLW geological repository

  9. Granular and layered ferroelectric–ferromagnetic thin-film nanocomposites as promising materials with high magnetotransmission effect

    Energy Technology Data Exchange (ETDEWEB)

    Akbashev, A.R. [Department of Materials Science, Moscow State University, 119992 Moscow (Russian Federation); Telegin, A.V., E-mail: telegin@imp.uran.ru [M.N. Miheev Institute of Metal Physics of Ural Branch of RAS, 620990 Ekaterinburg (Russian Federation); Kaul, A.R. [Department of Chemistry, Moscow State University, 119992 Moscow (Russian Federation); Sukhorukov, Yu.P. [M.N. Miheev Institute of Metal Physics of Ural Branch of RAS, 620990 Ekaterinburg (Russian Federation)

    2015-06-15

    Epitaxial thin films of granular and layered nanocomposites consisting of ferromagnetic perovskite Pr{sub 1–x}Sr{sub x}MnO{sub 3} and ferroelectric hexagonal LuMnO{sub 3} were grown on ZrO{sub 2}(Y{sub 2}O{sub 3}) substrates using metal-organic chemical vapor deposition (MOCVD). A self-organized growth of the granular composite took place in situ as a result of phase separation of the Pr–Sr–Lu–Mn–O system into the perovskite and hexagonal phases. Optical transmission measurements revealed a large negative magnetotransmission effect in the layered nanocomposite over a wide spectral and temperature range. The granular nanocomposite unexpectedly showed an even larger, but positive, magnetotransmission effect at room temperature. - Highlights: • Thin-film ferromagnetic–ferroelectric nanocomposites have been prepared by MOCVD. • Giant change of optical transparency of nanocomposites in magnetic field was detected. • Positive magnetotransmission in the granular nanocomposite was discovered in the IR. • Negative magnetotransmission in the layered nanocomposite was revealed in the IR. • Ferroelectric–ferromangetic nanocomposite is a promising material for optoelectronics.

  10. Granular and layered ferroelectric–ferromagnetic thin-film nanocomposites as promising materials with high magnetotransmission effect

    International Nuclear Information System (INIS)

    Akbashev, A.R.; Telegin, A.V.; Kaul, A.R.; Sukhorukov, Yu.P.

    2015-01-01

    Epitaxial thin films of granular and layered nanocomposites consisting of ferromagnetic perovskite Pr 1–x Sr x MnO 3 and ferroelectric hexagonal LuMnO 3 were grown on ZrO 2 (Y 2 O 3 ) substrates using metal-organic chemical vapor deposition (MOCVD). A self-organized growth of the granular composite took place in situ as a result of phase separation of the Pr–Sr–Lu–Mn–O system into the perovskite and hexagonal phases. Optical transmission measurements revealed a large negative magnetotransmission effect in the layered nanocomposite over a wide spectral and temperature range. The granular nanocomposite unexpectedly showed an even larger, but positive, magnetotransmission effect at room temperature. - Highlights: • Thin-film ferromagnetic–ferroelectric nanocomposites have been prepared by MOCVD. • Giant change of optical transparency of nanocomposites in magnetic field was detected. • Positive magnetotransmission in the granular nanocomposite was discovered in the IR. • Negative magnetotransmission in the layered nanocomposite was revealed in the IR. • Ferroelectric–ferromangetic nanocomposite is a promising material for optoelectronics

  11. Numerical insight into the micromechanics of jet erosion of a cohesive granular material

    Directory of Open Access Journals (Sweden)

    Cuéllar Pablo

    2017-01-01

    Full Text Available Here we investigate the physical mechanisms behind the surface erosion of a cohesive granular soil induced by an impinging jet by means of numerical simulations coupling fluid and grains at the microscale. The 2D numerical model combines the Discrete Element and Lattice Boltzmann methods (DEM-LBM and accounts for the granular cohesion with a contact model featuring a paraboloidal yield surface. Here we review first the hydrodynamical conditions imposed by the fluid jet on a solid granular packing, turning then the attention to the impact of cohesion on the erosion kinetics. Finally, the use of an additional subcritical debonding damage model based on the work of Silvani and co-workers provides a novel insight into the internal solicitation of the cohesive granular sample by the impinging jet.

  12. Numerical insight into the micromechanics of jet erosion of a cohesive granular material

    Science.gov (United States)

    Cuéllar, Pablo; Benseghier, Zeyd; Luu, Li-Hua; Bonelli, Stéphane; Delenne, Jean-Yves; Radjaï, Farhang; Philippe, Pierre

    2017-06-01

    Here we investigate the physical mechanisms behind the surface erosion of a cohesive granular soil induced by an impinging jet by means of numerical simulations coupling fluid and grains at the microscale. The 2D numerical model combines the Discrete Element and Lattice Boltzmann methods (DEM-LBM) and accounts for the granular cohesion with a contact model featuring a paraboloidal yield surface. Here we review first the hydrodynamical conditions imposed by the fluid jet on a solid granular packing, turning then the attention to the impact of cohesion on the erosion kinetics. Finally, the use of an additional subcritical debonding damage model based on the work of Silvani and co-workers provides a novel insight into the internal solicitation of the cohesive granular sample by the impinging jet.

  13. Pulling an intruder from a granular material: a novel depinning experiment

    Directory of Open Access Journals (Sweden)

    Zhang Yue

    2017-01-01

    Full Text Available Two-dimensional impact experiments by Clark et al. [2] identified the source of inertial drag to be caused by ‘collisions’ with a latent force network, leading to large fluctuations of the force experienced by the impactor. These collisions provided the major drag on an impacting intruder until the intruder was nearly at rest. As a complement, we consider controlled pull-out experiments where a buried intruder is pulled out of a material, starting from rest. This provides a means to better understand the non-inertial part of the drag force, and to explore the mechanisms associated with the force fluctuations. To some extent, the pull out process is a time reversed version of the impact process. In order to visualize this pulling process, we use 2D photoelastic disks from which circular intruders of different radii are pulled out. We present results about the dynamics of the intruder and the structures of the force chains inside the granular system as captured by slow and high speed imaging.

  14. Particle Damping with Granular Materials for Multi Degree of Freedom System

    Directory of Open Access Journals (Sweden)

    Masanobu Inoue

    2011-01-01

    Full Text Available A particle damper consists of a bed of granular materials moving in cavities within a multi degree-of-freedom (MDOF structure. This paper deals with the damping effects on forced vibrations of a MDOF structure provided with the vertical particle dampers. In the analysis, the particle bed is assumed to be a single mass, and the collisions between the granules and the cavities are completely inelastic, i.e., all energy dissipation mechanisms are wrapped into zero coefficient of restitution. To predict the particle damping effect, equations of motion are developed in terms of equivalent single degree-of-freedom (SDOF system and damper mass with use made of modal approach. In this report, the periodic vibration model comprising sustained contact on or separation of the damper mass from vibrating structure is developed. A digital model is also formulated to simulate the damped motion of the physical system, taking account of all vibration modes. Numerical and experimental studies are made of the damping performance of plural dampers located at selected positions throughout a 3MDOF system. The experimental results confirm numerical prediction that collision between granules and structures is completely inelastic as the contributing mechanism of damping in the vertical vibration. It is found that particle dampers with properly selected mass ratios and clearances effectively suppress the resonance peaks over a wide frequency range.

  15. Submicron and Nanoparticulate Matter Removal by HEPA-Rated Media Filters and Packed Beds of Granular Materials

    Science.gov (United States)

    Perry, J. L.; Agui, J. H.; Vijayakimar, R

    2016-01-01

    Contaminants generated aboard crewed spacecraft by diverse sources consist of both gaseous chemical contaminants and particulate matter. Both HEPA media filters and packed beds of granular material, such as activated carbon, which are both commonly employed for cabin atmosphere purification purposes have efficacy for removing nanoparticulate contaminants from the cabin atmosphere. The phenomena associated with particulate matter removal by HEPA media filters and packed beds of granular material are reviewed relative to their efficacy for removing fine (less than 2.5 micrometers) and ultrafine (less than 0.01 micrometers) sized particulate matter. Considerations are discussed for using these methods in an appropriate configuration to provide the most effective performance for a broad range of particle sizes including nanoparticulates.

  16. Field test of ethanol/bentonite slurry grouting into rock fracture

    International Nuclear Information System (INIS)

    Motoyuki Asada; Hitoshi Nakashima; Takashi Ishii; Sumio Horiuchi

    2006-01-01

    Crystalline rocks have fractures which may cause unexpected routes of groundwater seepage. Cement grouting is one of the most effective methods to minimize seepage; however, cement materials may not be suitable for the purpose of extra-long durability, because cement is neutralized or degraded by chemical and physical influence of chemical reaction. Natural clay like bentonite is one of the most promising materials for seepage barrier; however, water/bentonite grout is so viscous that enough amount of bentonite can not be grouted into rock fractures. To increase bentonite content in grout with low viscosity, the utilization of ethanol as a mixing liquid was studied. Ethanol suppresses bentonite swelling, and more bentonite can be injected more than that of water/bentonite slurry. In this paper, grouting into in-situ rock mass fracture from the ground surface was tested to investigate the barrier performance and workability of ethanol/bentonite slurry as a grouting material. (author)

  17. Bentonite. Geotechnical barrier and source for microbial life

    Energy Technology Data Exchange (ETDEWEB)

    Matschiavelli, Nicole; Kluge, Sindy; Cherkouk, Andrea [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). HZDR Young Investigator Group; Steglich, Jennifer

    2017-06-01

    Due to their properties, namely a high swelling capacity and a low hydraulic conductivity, Bentonites fulfil as geotechnical barrier a sealing and buffering function in the nuclear waste repository. Depending on the mineral composition Bentonites contain many suitable electron-donors and -acceptors, enabling potential microbial life. For the potential repository of highly radioactive waste the microbial mediated transformation of Bentonite could influence its properties as a barrier material. Microcosms were set up containing Bentonite and anaerobic synthetic Opalinus-clay-pore water solution under an N{sub 2}/CO{sub 2}-atmosphere to elucidate the microbial potential within selected Bentonites. Substrates like acetate and lactate were supplemented to stimulate potential microbial activity. First results show that bentonites represent a source for microbial life, demonstrated by the consumption of lactate and the formation of pyruvate. Furthermore, microbial iron-reduction was determined, which plays a crucial role in Betonite-transformation.

  18. Bentonite. Geotechnical barrier and source for microbial life

    International Nuclear Information System (INIS)

    Matschiavelli, Nicole; Kluge, Sindy; Cherkouk, Andrea; Steglich, Jennifer

    2017-01-01

    Due to their properties, namely a high swelling capacity and a low hydraulic conductivity, Bentonites fulfil as geotechnical barrier a sealing and buffering function in the nuclear waste repository. Depending on the mineral composition Bentonites contain many suitable electron-donors and -acceptors, enabling potential microbial life. For the potential repository of highly radioactive waste the microbial mediated transformation of Bentonite could influence its properties as a barrier material. Microcosms were set up containing Bentonite and anaerobic synthetic Opalinus-clay-pore water solution under an N_2/CO_2-atmosphere to elucidate the microbial potential within selected Bentonites. Substrates like acetate and lactate were supplemented to stimulate potential microbial activity. First results show that bentonites represent a source for microbial life, demonstrated by the consumption of lactate and the formation of pyruvate. Furthermore, microbial iron-reduction was determined, which plays a crucial role in Betonite-transformation.

  19. Earthquake induced rock shear through a deposition hole. Modelling of three model tests scaled 1:10. Verification of the bentonite material model and the calculation technique

    Energy Technology Data Exchange (ETDEWEB)

    Boergesson, Lennart (Clay Technology AB, Lund (Sweden)); Hernelind, Jan (5T Engineering AB, Vaesteraas (Sweden))

    2010-11-15

    Three model shear tests of very high quality simulating a horizontal rock shear through a deposition hole in the centre of a canister were performed 1986. The tests and the results are described by /Boergesson 1986/. The tests simulated a deposition hole in the scale 1:10 with reference density of the buffer, very stiff confinement simulating the rock, and a solid bar of copper simulating the canister. The three tests were almost identical with exception of the rate of shear, which was varied between 0.031 and 160 mm/s, i.e. with a factor of more than 5,000 and the density of the bentonite, which differed slightly. The tests were very well documented. Shear force, shear rate, total stress in the bentonite, strain in the copper and the movement of the top of the simulated canister were measured continuously during the shear. After finished shear the equipment was dismantled and careful sampling of the bentonite with measurement of water ratio and density were made. The deformed copper 'canister' was also carefully measured after the test. The tests have been modelled with the finite element code Abaqus with the same models and techniques that were used for the full scale scenarios in SR-Site. The results have been compared with the measured results, which has yielded very valuable information about the relevancy of the material models and the modelling technique. An elastic-plastic material model was used for the bentonite where the stress-strain relations have been derived from laboratory tests. The material model is made a function of both the density and the strain rate at shear. Since the shear is fast and takes place under undrained conditions, the density is not changed during the tests. However, strain rate varies largely with both the location of the elements and time. This can be taken into account in Abaqus by making the material model a function of the strain rate for each element. A similar model, based on tensile tests on the copper used in

  20. Bentonite-amended soils special study

    International Nuclear Information System (INIS)

    1990-10-01

    This report presents the results of a two-phased special study to evaluate the viability of soil amended with a high percentage of bentonite as an infiltration barrier in the cover of Uranium Mill Tailings Remedial Action (UMTRA) Project disposal cells. Phase I of the study was initiated in order to examine the feasibility of using bentonite-amended soils as a cover component on sideslopes and topslopes. The Phase I objectives were to test a variety of materials to determine if low hydraulic conductivities were achievable in materials exhibiting sufficient strength and to select suitable materials for further testing. Phase II objectives were to (1) optimize designs -- test materials with various percentages of bentonite added; (2) provide design recommendations; (3) address constructibility concerns; and (4) evaluate long-term performance with respect to desiccation effects on the amended materials

  1. A theoretical and numerical study of the flow of granular materials down an inclined plane. [Quarterly progress report, January--March 1995

    Energy Technology Data Exchange (ETDEWEB)

    Rajagopal, K.R.

    1995-09-01

    The mechanics of the flowing granular materials such as coal, agricultural products, fertilizers, dry chemicals, metal ores, etc. have received a great deal of attention as it has relevance to several important technological problems. Despite wide interest and more than five decades of experimental and theoretical investigations, most aspects of the behavior of flowing granular materials are still not well understood. So Experiments have to be devised which quantify and describe the non-linear behavior of the granular materials, and theories developed which can explain the experimentally observed facts. Here we carry out a systematic numerical study of the flow of granular materials down an inclined plane using the models that stem from both the continuum theory approach and the kinetic theory approach. We also look at the existence of solutions, multiplicity and stability of solutions to the governing equations.

  2. Planning for the Collection and Analysis of Samples of Martian Granular Materials Potentially to be Returned by Mars Sample Return

    Science.gov (United States)

    Carrier, B. L.; Beaty, D. W.

    2017-12-01

    NASA's Mars 2020 rover is scheduled to land on Mars in 2021 and will be equipped with a sampling system capable of collecting rock cores, as well as a specialized drill bit for collecting unconsolidated granular material. A key mission objective is to collect a set of samples that have enough scientific merit to justify returning to Earth. In the case of granular materials, we would like to catalyze community discussion on what we would do with these samples if they arrived in our laboratories, as input to decision-making related to sampling the regolith. Numerous scientific objectives have been identified which could be achieved or significantly advanced via the analysis of martian rocks, "regolith," and gas samples. The term "regolith" has more than one definition, including one that is general and one that is much more specific. For the purpose of this analysis we use the term "granular materials" to encompass the most general meaning and restrict "regolith" to a subset of that. Our working taxonomy includes the following: 1) globally sourced airfall dust (dust); 2) saltation-sized particles (sand); 3) locally sourced decomposed rock (regolith); 4) crater ejecta (ejecta); and, 5) other. Analysis of martian granular materials could serve to advance our understanding areas including habitability and astrobiology, surface-atmosphere interactions, chemistry, mineralogy, geology and environmental processes. Results of these analyses would also provide input into planning for future human exploration of Mars, elucidating possible health and mechanical hazards caused by the martian surface material, as well as providing valuable information regarding available resources for ISRU and civil engineering purposes. Results would also be relevant to matters of planetary protection and ground-truthing orbital observations. We will present a preliminary analysis of the following, in order to generate community discussion and feedback on all issues relating to: What are the

  3. Removal of oil from water by bentonite

    International Nuclear Information System (INIS)

    Moazed, H.; Viraraghavan, T.

    1999-01-01

    Many materials, included activated carbon, peat, coal, fiberglass, polypropylene, organoclay and bentonite have been used for removing oils and grease from water. However, bentonite has been used only rarely for this purpose. In this study Na-bentonite was used to remove oil from oil-in-water emulsions of various kinds such as standard mineral oil, cutting oils, refinery effluent and produced water from production wells at Estevan, Saskatchewan. Removal efficiencies obtained were 85 to 96 per cent for cutting oils, 84 to 86 per cent for produced water and 54 to 87 per cent for refinery effluent. Bentonite proved to be more effective in the removal of oil from oil-in-water emulsions than from actual waste waters; up to 96 percent from oil-in-water emulsions to only 87 per cent from actual waste water. The percentage of oil removed was found to be a function of the amount of bentonite added and the adsorption time up to the equilibrium time. Result also showed that the Langmuir, Freundlich and BET isotherms are well suited to describe the adsorption of oil by bentonite from the various oily waters employed in this study. 15 refs

  4. Numerical investigation of particle-blast interaction during explosive dispersal of liquids and granular materials

    Science.gov (United States)

    Pontalier, Q.; Lhoumeau, M.; Milne, A. M.; Longbottom, A. W.; Frost, D. L.

    2018-04-01

    Experiments show that when a high-explosive charge with embedded particles or a charge surrounded by a layer of liquid or granular material is detonated, the flow generated is perturbed by the motion of the particles and the blast wave profile differs from that of an ideal Friedlander form. Initially, the blast wave overpressure is reduced due to the energy dissipation resulting from compaction, fragmentation, and heating of the particle bed, and acceleration of the material. However, as the blast wave propagates, particle-flow interactions collectively serve to reduce the rate of decay of the peak blast wave overpressure. Computations carried out with a multiphase hydrocode reproduce the general trends observed experimentally and highlight the transition between the particle acceleration/deceleration phases, which is not accessible experimentally, since the particles are obscured by the detonation products. The dependence of the particle-blast interaction and the blast mitigation effectiveness on the mitigant to explosive mass ratio, the particle size, and the initial solid volume fraction is investigated systematically. The reduction in peak blast overpressure is, as in experiments, primarily dependent on the mass ratio of material to explosive, with the particle size, density, and initial porosity of the particle bed playing secondary roles. In the near field, the blast overpressure decreases sharply with distance as the particles are accelerated by the flow. When the particles decelerate due to drag, energy is returned to the flow and the peak blast overpressure recovers and reaches values similar to that of a bare explosive charge for low mass ratios. Time-distance trajectory plots of the particle and blast wave motion with the pressure field superimposed, illustrate the weak pressure waves generated by the motion of the particle layer which travel upstream and perturb the blast wave motion. Computation of the particle and gas momentum flux in the multiphase

  5. Numerical investigation of particle-blast interaction during explosive dispersal of liquids and granular materials

    Science.gov (United States)

    Pontalier, Q.; Lhoumeau, M.; Milne, A. M.; Longbottom, A. W.; Frost, D. L.

    2018-05-01

    Experiments show that when a high-explosive charge with embedded particles or a charge surrounded by a layer of liquid or granular material is detonated, the flow generated is perturbed by the motion of the particles and the blast wave profile differs from that of an ideal Friedlander form. Initially, the blast wave overpressure is reduced due to the energy dissipation resulting from compaction, fragmentation, and heating of the particle bed, and acceleration of the material. However, as the blast wave propagates, particle-flow interactions collectively serve to reduce the rate of decay of the peak blast wave overpressure. Computations carried out with a multiphase hydrocode reproduce the general trends observed experimentally and highlight the transition between the particle acceleration/deceleration phases, which is not accessible experimentally, since the particles are obscured by the detonation products. The dependence of the particle-blast interaction and the blast mitigation effectiveness on the mitigant to explosive mass ratio, the particle size, and the initial solid volume fraction is investigated systematically. The reduction in peak blast overpressure is, as in experiments, primarily dependent on the mass ratio of material to explosive, with the particle size, density, and initial porosity of the particle bed playing secondary roles. In the near field, the blast overpressure decreases sharply with distance as the particles are accelerated by the flow. When the particles decelerate due to drag, energy is returned to the flow and the peak blast overpressure recovers and reaches values similar to that of a bare explosive charge for low mass ratios. Time-distance trajectory plots of the particle and blast wave motion with the pressure field superimposed, illustrate the weak pressure waves generated by the motion of the particle layer which travel upstream and perturb the blast wave motion. Computation of the particle and gas momentum flux in the multiphase

  6. Corrosion of carbon steel in contact with bentonite

    International Nuclear Information System (INIS)

    Dobrev, D.; Vokal, A.; Bruha, P.

    2010-01-01

    Document available in extended abstract form only. Carbon steel canisters were chosen in a number of disposal concepts as reference material for disposal canisters. The corrosion rates of carbon steels in water solution both in aerobic and anaerobic conditions are well known, but only scarce data are available for corrosion behaviour of carbon steels in contact with bentonite. A special apparatus, which enables to measure corrosion rate of carbon steels under conditions simulating conditions in a repository, namely in contact with bentonite under high pressure and elevated temperatures was therefore prepared to study: - Corrosion rate of carbon steels in direct contact with bentonite in comparison with corrosion rate of carbon steels in synthetic bentonite pore water. - Influence of corrosion products on bentonite. The apparatus is composed of corrosion chamber containing a carbon steel disc in direct contact with compacted bentonite. Synthetic granitic water is above compacted bentonite under high pressure (50 - 100 bar) to simulate hydrostatic pressure in a repository. The experiments can be carried out under various temperatures. Bentonites used for experiments were Na-type of bentonite Volclay KWK 80 - 20 and Ca-Mg Czech bentonite from deposit Rokle. Before adding water into corrosion system the corrosion chamber was purged by nitrogen gas. The saturation of bentonite and corrosion rate were monitored by measuring consumption of water, pressure increase caused by swelling pressure of bentonite and by generation of hydrogen. Corrosion rate was also determined after corrosion experiments from weight loss of samples. The results of experiments show that the corrosion behaviour of carbon steels in contact with bentonite is very different from corrosion of carbon steels in water simulating bentonite pore water solution. The corrosion rates of carbon steel in contact with bentonite reached after 30 days of corrosion the values approaching 40 mm/yr contrary to values

  7. Evaluation of permeability and swelling pressure of compacted bentonite using a calcium hydroxide solution

    International Nuclear Information System (INIS)

    Aoyagi, Takayoshi; Maeda, Munehiro; Mihara, Morihiro; Tanaka, Masuhiro

    1998-12-01

    Tests to determine the swelling pressure, permeability, compressive strength and elastic modulus of Ca-Na exchanged bentonite, Na-bentonite and Ca-bentonite at the Power Reactor and Nuclear Fuel Development Corporation have mainly used distilled water. However, disposal facilities for TRU waste will use cementateous material for packaging, backfill as well as structural support. In this case, a large amount of calcium will dissolve in groundwater flowing through the cementateous material. Therefore, it is important to investigate the mechanical properties of bentonite in calcium-rich water as part of the disposal research program for TRU waste. In order to understand the effect of the chemical composition of water on the basic mechanical properties of bentonite - part of evaluating the disposal concepts for TRU waste disposal - we tested the permeability of compacted bentonite under saturated conditions using a calcium hydroxide solution. The aqueous solution represents water dominated by the calcium component. Na-bentonite, Ca-Na exchanged bentonite and Ca-bentonite were used for swelling pressure measurement tests and permeability testing. Measures of the maximum and equilibrium swelling pressure as well as permeability we obtained. The dry density of bentonite was varied between tests. Results show that swelling pressure and permeability are dependent on dry density. In separate tests using Ca-bentonite, the bentonite-mixing rate was varied as an independent parameter. Results show that there is little change in the swelling pressure and permeability between tests using calcium hydroxide solution and distilled water for all bentonite types. (author)

  8. A comparison of nano bentonite and some nano chemical additives to improve drilling fluid using local clay and commercial bentonites

    Directory of Open Access Journals (Sweden)

    Nada S. Al-Zubaidi

    2017-09-01

    In the second part, a commercial bentonite was used and mixed with nano commercial bentonite and nano chemical materials (MgO, TiO2, and graphene at 0.005, 0.01, 0.05, 0.1, 0.2 and 0.4 wt% concentrations. The results showed that nano commercial bentonite gives the same filtration behavior of graphene, whereas, the plastic viscosity, yield point and apparent viscosity were the same when using nano commercial bentonite, TiO2 and graphene. The best results were obtained with MgO addition, whereby the filter loss decreased to 35% with a higher value of yield point.

  9. Bentonite Permeability at Elevated Temperature

    Directory of Open Access Journals (Sweden)

    Katherine A. Daniels

    2017-01-01

    Full Text Available Repository designs frequently favour geological disposal of radioactive waste with a backfill material occupying void space around the waste. The backfill material must tolerate the high temperatures produced by decaying radioactive waste to prevent its failure or degradation, leading to increased hydraulic conductivity and reduced sealing performance. The results of four experiments investigating the effect of temperature on the permeability of a bentonite backfill are presented. Bentonite is a clay commonly proposed as the backfill in repository designs because of its high swelling capacity and very low permeability. The experiments were conducted in two sets of purpose-built, temperature controlled apparatus, designed to simulate isotropic pressure and constant volume conditions within the testing range of 4–6 MPa average effective stress. The response of bentonite during thermal loading at temperatures up to 200 °C was investigated, extending the previously considered temperature range. The results provide details of bentonite’s intrinsic permeability, total stress, swelling pressure and porewater pressure during thermal cycles. We find that bentonite’s hydraulic properties are sensitive to thermal loading and the type of imposed boundary condition. However, the permeability change is not large and can mostly be accounted for by water viscosity changes. Thus, under 150 °C, temperature has a minimal impact on bentonite’s hydraulic permeability.

  10. Swelling characteristics of Gaomiaozi bentonite and its prediction

    Directory of Open Access Journals (Sweden)

    De'an Sun

    2014-04-01

    Full Text Available Gaomiaozi (GMZ bentonite has been chosen as a possible matrix material of buffers/backfills in the deep geological disposal to isolate the high-level radioactive waste (HLRW in China. In the Gaomiaozi deposit area, calcium bentonite in the near surface zone and sodium bentonite in the deeper zone are observed. The swelling characteristics of GMZ sodium and calcium bentonites and their mixtures with sand wetted with distilled water were studied in the present work. The test results show that the relationship between the void ratio and swelling pressure of compacted GMZ bentonite-sand mixtures at full saturation is independent of the initial conditions such as the initial dry density and water content, but dependent on the ratio of bentonite to sand. An empirical method was accordingly proposed allowing the prediction of the swelling deformation and swelling pressure with different initial densities and bentonite-sand ratios when in saturated conditions. Finally, the swelling capacities of GMZ Na- and Ca-bentonites and Kunigel Na-bentonite are compared.

  11. Analysis of corrosion products of carbon steel in wet bentonite

    International Nuclear Information System (INIS)

    Osada, Kazuo; Nagano, Tetsushi; Nakayama, Shinichi; Muraoka, Susumu

    1992-02-01

    As a part of evaluation of the long-term durability for the overpack containers for high-level radioactive waste, we have conducted corrosion tests for carbon steel in wet bentonite, a candidate buffer material. The corrosion rates were evaluated by weight difference of carbon steel and corrosion products were analyzed by Fourier transform infrared spectroscopy (FT-IR) and colorimetry. At 40degC, the corrosion rate of carbon steel in wet bentonite was smaller than that in pure water. At 95degC, however, the corrosion rate in wet bentonite was much higher than that in pure water. This high corrosion rate in wet bentonite at 95degC was considered to result from evaporation of moisture in bentonite in contact with the metal. This evaporation led to dryness and then to shrinkage of the bentonite, which generated ununiform contact of the metal with bentonite. Probably, this ununiform contact promoted the local corrosion. The locally corroded parts of specimen in wet bentonite at 95degC were analyzed by Fourier transform infrared microspectroscopy (micro-FT-IR), and lepidocrocite γ-FeO(OH) was found as well as goethite α-FeO(OH). In wet bentonite at 95degC, hematite α-Fe 2 O 3 was identified by means of colorimetry. (author)

  12. MANU. Handling of bentonite prior buffer block manufacturing

    International Nuclear Information System (INIS)

    Laaksonen, R.

    2010-01-01

    The aim of this study is to describe the entire bentonite handling process starting from freight from harbour to storage facility and ending up to the manufacturing filling process of the bentonite block moulds. This work describes the bentonite handling prior to the process in which bentonite blocks are manufactured in great quantities. This work included a study of relevant Nordic and international well documented cases of storage, processing and techniques involving bentonite material. Information about storage and handling processes from producers or re-sellers of bentonite was collected while keeping in mind the requirements coming from the Posiva side. Also a limited experiment was made for humidification of different material types. This work includes a detailed description of methods and equipment needed for bentonite storage and processing. Posiva Oy used Jauhetekniikka Oy as a consultant to prepare handling process flow charts for bentonite. Jauhetekniikka Oy also evaluated the content of this report. The handling of bentonite was based on the assumption that bentonite process work is done in one factory for 11 months of work time while the weekly volume is around 41-45 tons. Storage space needed in this case is about 300 tons of bentonite which equals about seven weeks of raw material consumption. This work concluded several things to be carefully considered: sampling at various phases of the process, the air quality at the production/storage facilities (humidity and temperature), the level of automation/process control of the manufacturing process and the means of producing/saving data from different phases of the process. (orig.)

  13. A theoretical and numerical study of the flow of granular materials down an inclined plane. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Rajagopal, K.R.

    1995-12-31

    The mechanics of the flowing granular materials such as coal, agricultural products, at deal of attention as it has fertilizers, dry chemicals, metal ores, etc. have received a great deal of attention as it has relevance to several important technological problems. Despite wide interest and more than five decades of experimental and theoretical investigations, most aspects of the behavior of flowing granular materials are still not well understood. So Experiments have to be devised which quantify and describe the non-linear behavior of the modular materials, and theories developed which can explain the experimentally observed facts. As many models have been suggested for describing the behavior of granular materials, from both continuum and kinetic theory viewpoints, we proposed to investigate the validity and usefulness of representative models from both the continuum and kinetic theory points of view, by determining the prediction of such a theory, in a representative flow, with respect to existence, non-existence, multiplicity and stability of solutions. The continuum model to be investigated is an outgrowth of a model due to Goodman and Cowin (1971, 1972) and the kinetic theory models being those due to Jenkins and Richman (1985) and Boyle and Massoudi (1989). In this report we present detailed results regarding the same. Interestingly, we find that the predictions of all the theories, in certain parameter space associated with these models, are qualitatively similar. This ofcourse depends on the values assumed for various material parameters in the models, which as yet are unknown, as reliable experiments have not been carried out as yet for their determination.

  14. Understanding creep in sandstone reservoirs - theoretical deformation mechanism maps for pressure solution in granular materials

    Science.gov (United States)

    Hangx, Suzanne; Spiers, Christopher

    2014-05-01

    -boundary diffusion and precipitation on pore walls. As a first step to better describe creep in sands and sandstones, we have derived a simple model for intergranular pressure solution (IPS) within an ordered pack of spherical grains, employing existing IPS rate models, such as those derived by Renard et al. (1999) and Spiers et al. (2004). This universal model is able to predict the conditions under which each of the respective pressure solution serial processes, i.e. diffusion, precipitation or dissolution, is dominant. In essence, this creates generic deformation mechanism maps for any granular material. We have used our model to predict the amount and rate of compaction for sandstone reservoirs, and compared our predictions to known subsidence rates for reservoirs around the world. This gives a first order-comparison to verify whether or not IPS is an important mechanism in controlling reservoir compaction.

  15. Sound propagation in dry granular materials : discrete element simulations, theory, and experiments

    NARCIS (Netherlands)

    Mouraille, O.J.P.

    2009-01-01

    In this study sound wave propagation through different types of dry confined granular systems is studied. With three-dimensional discrete element simulations, theory and experiments, the influence of several micro-scale properties: friction, dissipation, particle rotation, and contact disorder, on

  16. Microbial activity in bentonite buffers. Literature study

    Energy Technology Data Exchange (ETDEWEB)

    Ratto, M.; Itavaara, M.

    2012-07-01

    The proposed disposal concept for high-level radioactive wastes involves storing the wastes underground in copper-iron containers embedded in buffer material of compacted bentonite. Hydrogen sulphide production by sulphate-reducing prokaryotes is a potential mechanism that could cause corrosion of waste containers in repository conditions. The prevailing conditions in compacted bentonite buffer will be harsh. The swelling pressure is 7-8 MPa, the amount of free water is low and the average pore and pore throat diameters are small. This literature study aims to assess the potential of microbial activity in bentonite buffers. Literature on the environmental limits of microbial life in extreme conditions and the occurrence of sulphatereducing prokaryotes in extreme environments is reviewed briefly and the results of published studies characterizing microbes and microbial processes in repository conditions or in relevant subsurface environments are presented. The presence of bacteria, including SRBs, has been confirmed in deep groundwater and bentonite-based materials. Sulphate reducers have been detected in various high-pressure environments, and sulphate-reduction based on hydrogen as an energy source is considered a major microbial process in deep subsurface environments. In bentonite, microbial activity is strongly suppressed, mainly due to the low amount of free water and small pores, which limit the transport of microbes and nutrients. Spore-forming bacteria have been shown to survive in compacted bentonite as dormant spores, and they are able to resume a metabolically active state after decompaction. Thus, microbial sulphide production may increase in repository conditions if the dry density of the bentonite buffer is locally reduced. (orig.)

  17. Thermal transport in lithium ion batteries: An experimental investigation of interfaces and granular materials

    Science.gov (United States)

    Gaitonde, Aalok Jaisheela Uday

    Increasing usage and recent accidents due to lithium-ion (Li-ion) batteries exploding or catching on fire has inspired research on the characterization and thermal management of these batteries. In cylindrical 18650 cells, heat generated during the battery's charge/discharge cycle is poorly dissipated to the surrounding through its metallic case due to the poor thermal conductivity of the jelly roll, which is spirally wound with many interfaces between electrodes and the polymeric separator. This work presents a technique to measure the thermal conduction across the metallic case-plastic separator interface, which ultimately limits heat transfer out of the jelly roll. The polymeric separator and metallic case are harvested from discharged commercial 18650 battery cells for thermal testing. A miniaturized version of the reference bar method enables measurements of the interface resistance between the case and the separator by establishing a temperature gradient across a multilayer stack consisting of two reference layers of known thermal conductivity and the case-separator sample. The case-separator interfacial conductance is reported for a range of case temperatures and interface pressures. The mean thermal conductance across the case-separator interface is 670 +/- 275 W/(m2K) and no significant temperature or pressure dependence is observed. The effective thermal conductivity of the battery stack is measured to be 0.27 W/m/K and 0.32 W/m/K in linear and radial configurations, respectively. Many techniques for fabricating battery electrodes involve coating particles of the active materials on metallic current collectors. The impact of mechanical shearing on the resultant thermal properties of these packed particle beds during the fabrication process has not yet been studied. Thus, the final portion of this thesis designs and validates a measurement system to measure the effects of mechanical shearing on the thermal conductivity of packed granular beds. This system

  18. Bentonite-amended soil special study

    International Nuclear Information System (INIS)

    1989-12-01

    This special study was conducted to assess the viability of soil with a high percentage of bentonite added as an infiltration barrier in the cover of Uranium Mill Tailings Remedial Action (UMTRA) Project disposal cells. To achieve maximum concentration limits (MCLs) at several UMTRA Project sites, covers with a very low permeability are needed. If alternate concentration limits (ACLs) are the appropriate site groundwater compliance strategy, the US Department of Energy (DOE) is required to demonstrate, among other things, that the infiltration to the disposal cell is as low as reasonably achievable, and hence that the cover has a very low permeability. When the study discussed here was begun, the lowest permeability element available was CLAYMAX R , a manufactured liner material constructed of natural material (bentonite clay) between two geosynthetics.The strength of soil-bentonite mixes was measured to see if they could be placed on sideslopes and not pose stability problems. Also evaluated were the hydraulic conductivities of soil-bentonite mixes. If the strengths and permeabilities of soils with a high percentage of bentonite are favorable, the soils may be used as infiltration barriers in current cover designs without changing pile geometries. The scope of work for this study called for a literature review and a two-phased laboratory testing program. This report presents the results of the literature review and the first phase of the testing program

  19. In-situ experiments on bentonite-based buffer and sealing materials at the Mont Terri rock laboratory (Switzerland)

    Energy Technology Data Exchange (ETDEWEB)

    Wieczorek, K. [Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) GmbH, Braunschweig (Germany); Gaus, I. [National Cooperative for the Disposal of Radioactive Waste (NAGRA), Wettingen (Switzerland); Mayor, J. C. [Empresa Nacional de Residuos Radiactivos SA (ENRESA), Madrid (Spain); and others

    2017-04-15

    Repository concepts in clay or crystalline rock involve bentonite-based buffer or seal systems to provide containment of the waste and limit advective flow. A thorough understanding of buffer and seal evolution is required to make sure the safety functions are fulfilled in the short and long term. Experiments at the real or near-real scale taking into account the interaction with the host rock help to make sure the safety-relevant processes are identified and understood and to show that laboratory-scale findings can be extrapolated to repository scale. Three large-scale experiments on buffer and seal properties performed in recent years at the Mont Terri rock laboratory are presented in this paper: The 1:2 scale HE-E heater experiment which is currently in operation, and the full-scale engineered barrier experiment and the Borehole Seal experiment which have been completed successfully in 2014 and 2012, respectively. All experiments faced considerable difficulties during installation, operation, evaluation or dismantling that required significant effort to overcome. The in situ experiments show that buffer and seal elements can be constructed meeting the expectations raised through small-scale testing. It was, however, also shown that interaction with the host rock caused additional effects in the buffer or seal that could not always be quantified or even anticipated from the experience of small-scale tests (such as re-saturation by pore-water from the rock, interaction with the excavation damaged zone in terms of preferential flow or mechanical effects). This led to the conclusion that testing of the integral system buffer/rock or seal/rock is needed. (authors)

  20. Soil-bentonite design mix for slurry cutoff walls used as containment barriers

    International Nuclear Information System (INIS)

    Rad, N.S.; Bachus, R.C.; Jacobson, B.D.

    1995-01-01

    In recent years, soil-bentonite slurry cutoff walls have been increasingly used as containment barriers around contaminated soils to impede or, in some cases, nearly eliminate the off-site migration of contaminated ground water or other potentially hazardous liquids. The paper presents the procedures used and the results obtained during an extensive laboratory testing program performed to select varying soil-bentonite slurry mix components for a soil-bentonite slurry cutoff wall constructed around an old landfill at a former oil refinery. The landfill is underlain to varying depths by a coarse granular soils that has been exposed to oil-products. Compatibility of three commercially available bentonite products with the free oil-products and the oil-contaminated ground water found at some locations in the landfill was initially investigated. Based on the test results, one of the bentonite products was selected for use in the soil-bentonite slurry testing program. A clayey soil from a borrow source, potable water from the site, and subsurface soils from the proposed soil-bentonite slurry wall alignment were used to form different soil-bentonite slurry mixes. Slump tests were performed to evaluate the workability of the mixes. Based on the test results, a single mix was selected for further study, including permeability/compatibility testing. The results of the compatibility testing program are presented and discussed in the paper. A specific design mix methodology for evaluating the chemical compatibility of soil-bentonite slurry mixes with permeants is proposed

  1. Fabrication and handling of bentonite blocks

    International Nuclear Information System (INIS)

    1978-06-01

    In accordance with the project for the final storage of spent nuclear fuel, the waste will be encapsulated into copper canisters, which will be deposited in a final repository located in rock 500 m below ground level. The canisters will be placed in vertical holes in the bottoms of the tunnels, where the copper cylinders will be surrounded by blocks of highly compacted bentonite. When the blocks are saturated with water and expansion is essentially retained as in the actual case, a very high swelling pressure will arise. The bentonite will be extremely impermeable and thus it will form a barrier against transport of corrosive matters to the canister. The blocks are fabricated by means of cold isostatic pressing of bentonite powder. The base material in the form of powder is enclosed in flexible forms, which are introduced into pressure vessels where the forms are surrounded by oil or water. Thus the powder is compacted into rigid bodies with a bulk density of about 2.2 t/m 3 for ''air dry'' bentonite, which might be compared with a specific density of about 2.7 t/m 3 . The placing of a canister is preceded by piling up bentonite blocks to a level just below the canister lid position, after which the slot around the blocks is filled with bentonite powder. The rest of the blocks are mounted after filling bentonite powder into the inner slot around the canister as well. Finally the storage tunnels will be sealed by filling them with a mixture o02067NRM 0000181 45

  2. Computational study on the behaviors of granular materials under mechanical cycling

    International Nuclear Information System (INIS)

    Wang, Xiaoliang; Ye, Minyou; Chen, Hongli

    2015-01-01

    Considering that fusion pebble beds are probably subjected to the cyclic compression excitation in their future applications, we presented a computational study to report the effect of mechanical cycling on the behaviors of granular matter. The correctness of our numerical experiments was confirmed by a comparison with the effective medium theory. Under the cyclic loads, the fast granular compaction was observed to evolve in a stretched exponential law. Besides, the increasing stiffening in packing structure, especially the decreasing moduli pressure dependence due to granular consolidation, was also observed. For the force chains inside the pebble beds, both the internal force distribution and the spatial distribution of force chains would become increasingly uniform as the external force perturbation proceeded and therefore produced the stress relief on grains. In this case, the originally proposed 3-parameter Mueth function was found to fail to describe the internal force distribution. Thereby, its improved functional form with 4 parameters was proposed here and proved to better fit the data. These findings will provide more detailed information on the pebble beds for the relevant fusion design and analysis

  3. Influence of selected factors on strontium sorption on bentonites

    International Nuclear Information System (INIS)

    Galambos, M.; Kufcakova, J.; Rajec, P.

    2007-01-01

    Sorption on bentonite will play an important role in retarding the migration of radionuclides from a waste repository. Bentonite is a natural clay and one of the most promising candidates for use as a buffer material in the geological disposal systems for high-level nuclear waste. It is intended to isolate metal canisters with highly radioactive waste products from the surrounding rocks because of its ability to retard the movement of radionuclides by sorption. Bentonite is characterized by low permeability, water swelling capability and excellent sorption potential for cationic radionuclides. To correctly assess the sorption potential of radionuclides on bentonite is essential for the development of predictive migration models. The sorption of strontium on bentonite from different Slovak deposits - Jelsovy potok, Kopernica and Lieskovec has been investigated under various experimental conditions, such as contact time, sorbate concentrations, presence of complementary cation. Sorption was studied using the batch technique. The uptake of Sr was rapid and equilibrium was reached almost instantaneously. The instantaneous uptake may be due to adsorption and/or exchange of the metal with some ions on the surface of the adsorbent. The best sorption characteristics distinguish bentonite Kopernica, sorption capacity for Sr of the fraction under 45 mm is 0,48 mmol·g -1 for Sr. The highest values of distribution coefficient were reached for the bentonite Jelsovy potok. Radiation stability has been investigated, the higher sorption parameters were observed for the irradiated bentonites, which can be explained by the increase of specific surface of the bentonite samples. The presence of complementary cations depresses the sorption of Sr on bentonite. Cations Ca 2+ exhibit higher effect on cesium sorption than the Na 2+ ions. Results indicate that the sorption of Sr 2+ on bentonite will be affected by the presence of high concentrations of various salts in the waste water

  4. The contact heat transfer between the heating plate and granular materials in rotary heat exchanger under overloaded condition

    Directory of Open Access Journals (Sweden)

    Luanfang Duan

    2018-03-01

    Full Text Available In the present work, the contact heat transfer between the granular materials and heating plates inside plate rotary heat exchanger (PRHE was investigated. The heat transfer coefficient is dominated by the contact heat transfer coefficient at hot wall surface of the heating plates and the heat penetration inside the solid bed. A plot scale PRHE with a diameter of Do = 273 mm and a length of L = 1000 mm has been established. Quartz sand with dp = 2 mm was employed as the experimental material. The operational parameters were in the range of ω = 1 – 8 rpm, and F = 15, 20, 25, 30%, and the effect of these parameters on the time-average contact heat transfer coefficient was analyzed. The time-average contact heat transfer coefficient increases with the increase of rotary speed, but decreases with the increase of the filling degree. The measured data of time-average heat transfer coefficients were compared with theoretical calculations from Schlünder’s model, a good agreement between the measurements and the model could be achieved, especially at a lower rotary speed and filling degree level. The maximum deviation between the calculated data and the experimental data is approximate 10%. Keywords: Rotary heat exchanger, Contact heat transfer, Granular material, Heating plate, Overloaded

  5. Granular gas dynamics

    CERN Document Server

    Brilliantov, Nikolai

    2003-01-01

    While there is not yet any general theory for granular materials, significant progress has been achieved for dilute systems, also called granular gases. The contributions in this book address both the kinetic approach one using the Boltzmann equation for dissipative gases as well as the less established hydrodynamic description. The last part of the book is devoted to driven granular gases and their analogy with molecular fluids. Care has been taken so as to present the material in a pedagogical and self-contained way and this volume will thus be particularly useful to nonspecialists and newcomers to the field.

  6. Sorption behavior of cesium onto bentonite colloid

    International Nuclear Information System (INIS)

    Iijima, Kazuki; Masuda, Tsuguya; Tomura, Tsutomu

    2004-01-01

    It is considered that bentonite colloid might be generated from bentonite which will be used as buffer material in geological disposal system, and can facilitate the migration of radionuclides by means of sorption. In order to examine this characteristic, sorption and desorption experiments of Cs onto bentonite colloid were carried out to obtain its distribution coefficient (Kd) and information on the reversibility of its sorption. In addition, particle size distribution and shape of colloid were investigated and their effect on the sorption behavior was discussed. Kds for Cs were around 20 m 3 /kg for sorption and 30 m 3 /kg for desorption, in which sorbed Cs was desorbed by 8.4x10 -4 mol/l of NaCl solution. These values did not show any dependencies on Cs concentration and duration of sorption and desorption. The first 20% of sorbed Cs was desorbed reversibly at least. Most of colloidal particles were larger than 200 nm and TEM micrographs showed they had only several sheets of the clay crystal. Obtained Kds for colloidal bentonite were larger than those for powdered bentonite. This can be caused by difference of competing ions in the solution, characteristics of contained smectite, or sorption site density. (author)

  7. Influence factors of sand-bentonite mixtures on hydraulic conductivity

    International Nuclear Information System (INIS)

    Chen Yonggui; Ye Weimin; Chen Bao; Wan Min; Wang Qiong

    2008-01-01

    Buffer material is a very important part of the engineering barrier for geological disposal of high-level radioactive nuclear waste. Compacted bentonite is attracting greater attention as buffer and backfill material because it offer impermeability and swelling properties, but the pure compacted bentonite strength decreases with increasing hydration and these will reduce the buffer capability. To solve this problem, sand is often used to form compacted sand-bentonite mixtures (SBMs) providing high thermal conductivity, excellent compaction capacity, long-time stability, and low engineering cost. As to SBMs, hydraulic conductivity is a important index for evaluation barrier capability. Based on the review of research results, the factors affecting the hydraulic conductivity of SBMs were put forward including bentonite content, grain size distribution, moisture content, dry density, compacting method and energy, and bentonite type. The studies show that the hydraulic conductivity of SBMs is controlled by the hydraulic conductivity of the bentonite, it also decreases as dry density and bentonite content increase, but when the bentonite content reach a critical point, the influence of increasing bentonite to decrease the hydraulic conductivity is limited. A fine and well-graded SBMs is likely to have a lower hydraulic conductivity than a coarse and poorly graded material. The internal erosion or erodibility based on the grain size distribution of the SBMs has a negative effect on the final hydraulic conductivity. The lowest hydraulic conductivity is gained when the mixtures are compacted close to optimum moisture content. Also, the mixtures compacted at moisture contents slightly above optimum values give lower hydraulic conductivity than when compacted at slightly under the optimum moisture content. Finally, discussion was brought to importance of compaction method, compacting energy, and bentonite type to the hydraulic conductivity of SBMs. (authors)

  8. MANU. Purchase of Bentonite. Process Description

    International Nuclear Information System (INIS)

    Laaksonen, R.

    2010-01-01

    The aim of this study is to describe the entire bentonite purchasing process accurately. This will enable efficient and focused use of information related to the purchasing phase and to each individual bentonite batch. This work continues from the work started in the report by Ahonen et al. (2008), Quality Assurance of the Bentonite Material, Posiva Working Report 2008-33. The current work includes a short enquiry for all relevant and at the time known producers or re-sellers of bentonite. Questions about relevant products suitable for civil engineering use, more specifically nuclear waste disposal site use, were asked together with test methods, typical test results and test standards. The following aspects and opinions have been processed from the results that were obtained during the project. Each seller/producer has a quality management system, QMS (typically ISO 9001), and ability to perform the basic tests, but there is not an established common set of properties to be tested. Some producers are willing to test according to customers' specifications. Posiva could arrange a network of capable laboratories to carry out tests according to its selected standards. This activity should then be accredited with a reasonable testing volume. Before starting the purchase of bentonite at a large scale, Posiva should go through negotiations and audits with each seller in order to make sure that both parties are testing with the same methods and both understand the range where the values of key parameters may lie. A database is needed for gathering statistically relevant information from the bentonite material parameters over the long run. This is needed for determining the limits within which the material parameters should remain in order to be acceptable. Posiva is encouraged to create a process to optimize the test types and the amount of tests should be identified for immediate and long term use. This process ensures the required quality and costs involved. (orig.)

  9. Investigation of the selected properties of dusts from the reclamation of spent sands with bentonite

    Directory of Open Access Journals (Sweden)

    J. Kamińska

    2011-10-01

    Full Text Available The investigation results of the selected properties of dusts generated during the mechanical reclamation of spent sands with bentonite as well as dusts from the dedusting system of sand processing plant are presented in the hereby paper. Investigations were performed with regard to determination conditions allowing to pelletise dusts in the bowl granulator. The verified methods of testing physical and chemical dust properties such as: specific density, bulk density of loosely put materials and apparent density of compacted materials together with their corresponding porosity, ignition losses and pH values, were applied. Granular composition of dusts generated during abrasion of spent binding materials in mechanical dry reclamation processes of spent sands with bentonite and coal dusts were performed by the laser diffraction analysis, allowing to broaden the measuring range of particle diameters. The optimal wetting agent content (in this case water at which the dust-water mixture obtains the best strength properties – after compacting by means of the standard moulder’s rammer – was determined.

  10. Diffusion behavior for Se and Zr in sodium-bentonite

    International Nuclear Information System (INIS)

    Sato, Haruo; Yui, Mikazu; Yoshikawa, Hideki

    1995-01-01

    Apparent diffusion coefficients for Se and Zr in bentonite were measured by in-diffusion method at room temperature using water-saturated sodium-bentonite, Kunigel V1 reg-sign containing 50wt% Na-smectite as a major mineral was used as the bentonite material. The experiments were carried out in the dry density range of 400--1,800 kg/m 3 . Bentonite samples were immersed with distilled water and saturated before the experiments. The experiments for Se were carried out under N 2 atmospheric condition (O 2 : 2.5ppm). Those for Zr were carried out under aerobic condition. The apparent diffusion coefficients decrease with increasing density of the bentonite. Since dominant species of Se in the pore water is predicted to be SeO 3 2- , Se may be retarded by anion-exclusion because of negative charge on the surface of the bentonite and little sorption. The dominant species of Zr in the porewater is predicted to be Zr(OH) 5 - or HZrO 3 - . Distribution coefficient measured for Zr on the bentonite was about 1.0 m 3 /kg from batch experiments. Therefore, the retardation may be caused by combination of the sorption and the anion-exclusion. A modeling for the diffusion mechanisms in the bentonite were discussed based on an electric double layer theory. Comparison between the apparent diffusion coefficients predicted by the model and the measured ones shows a good agreement

  11. Preparation and characterization of bentonite organo clay

    International Nuclear Information System (INIS)

    Bertagnolli, C.; Almeida Neto, A.F.; Silva, M.G.C.

    2009-01-01

    Bentonite clays organically modified have great potential use for environmental remediation, especially in the separation of organic compounds from the water. The aim of this work was the preparation of organophilic clays from 'Verde-Lodo' bentonite clay with the quaternary ammonium salts cetyl-pyridinium chloride and benzalkonium chloride. The materials obtained were characterized by XRD, thermogravimetric analyses, Helium picnometry, SEM and energy dispersive X-ray techniques. The results show consistently successful synthesis of the organoclay through the increase in the basal spacing, as well as salt elimination picks and presence of carbon and chlorine in the modified clays; they are inexistent elements in the natural clay. (author)

  12. What Actually Happens When Granular Materials Deform Under Shear: A Look Within

    Science.gov (United States)

    Viggiani, C.

    2012-12-01

    depends on the quality of the physics one injects: ideally, this comes directly from experiments. In Grenoble, this is what we do, combining various advanced experimental techniques. We are able to image, in three dimensions and at small scales, the deformation processes accompanying failure in geomaterials. This allows us to understand these processes and subsequently to define models at a pertinently small scale. I will present a few examples of the kind of experimental results which could inform a micro scale model. X-ray micro tomography imaging is the key measurement tool. This is used during loading, providing complete 3D images of a sand specimen at several stages throughout a triaxial compression test. Images from x-rays are then analyzed either in a continuum sense (using 3D Digital Image Correlation) or looking at the individual particle kinematics (Particle Tracking). I will show some of our most recent results, in which individual sand grains are followed with a technique combining very recent developments in image correlation and particle tracking. These advanced techniques offer us a look at what actually happens when a granular material deforms and eventually fails.

  13. Survey on current status of laboratory test method and experimental consideration for establishing standardized procedure of material containing bentonite. Report of collaboration research between JAEA and CRIEPI (Joint research)

    International Nuclear Information System (INIS)

    Tanai, Kenji; Kikuchi, Hirohito; Nakamura, Kunihiko; Tanaka, Yukihisa; Hironaga, Michihiko

    2010-08-01

    In the current concept of repository for radioactive waste disposal, compacted bentonite as well as bentonite based material will be used as an engineered barrier mainly for inhibiting migration of radioactive nuclides. In most cases, properties of bentonite, such as low permeability etc., are obtained by laboratory tests. However, results of laboratory tests of bentonite often vary considerably even if index parameter, such as effective clay density, is constant. One of the causes of the variability is considered to be lack of standardized method of laboratory test for bentonite. Thus standardization of laboratory test methods for bentonite is needed. So, investigation for establishing standardized laboratory test method of bentonite is conducted based on the results of survey on current status of laboratory test method for bentonite. In particular, the literature survey as well as laboratory tests were conducted to find factors affecting the results of laboratory tests for bentonite and to estimate their degree of influence. The following conclusions are obtained through this study. (1) Hydraulic conductivity test. According to the results of literature survey, it is revealed that constant pressure permeability test and consolidation test are currently used for measuring hydraulic conductivity of bentonite and that (a) hydraulic gradient, (b) local seepage flow between lateral surface of the specimen and lateral wall of the container, (c) water pressure which is applied to the specimen, (d) degree of saturation and (e) size of the specimen possibly affect the results of the constant pressure permeability test, while (f) friction between lateral surface of the specimen and lateral wall of the container accompanied by deformation of the specimen, (g) consolidation pressure together with factors (d), (e) affect the results of the consolidation test. Literature which describes that factors (a), (b) and (e) affect the results of the constant pressure permeability test

  14. An approach to discriminatively determine thoron and radon emanation rates for a granular material with a scintillation cell

    International Nuclear Information System (INIS)

    Sakoda, Akihiro; Meisenberg, Oliver; Tschiersch, Jochen

    2016-01-01

    A powder sandwich technique was applied to determine thoron ("2"2"0Rn) and radon ("2"2"2Rn) emanation rates for a granular material. The feature of this technique is the sample preparation, in which a granular material is put and fixed between two membrane filters. Airflow is directly given to this sandwich sample, will include thoron and radon emanated from the material, and then is transferred to the detector. This method makes sure that thoron and radon emanated are not retained in pore space within the sample volume, which is crucial for the appropriate emanation test. This technique was first introduced by Kanse et al. (2013) with the intention to measure the emanation of thoron - but not of radon - from materials having much higher "2"2"4Ra activity than "2"2"6Ra. In the present study, the methodology for the discriminative determination of thoron and radon emanation rates from a granular material has been examined using a flow-through scintillation cell and sandwich sample. The mathematical model was developed to differentiate total alpha counts into thoron- and radon-associated counts. With a sample of uranium ore, this model was experimentally validated by comparison between the scintillation cell and a reference detector that can discriminatively measure thoron and radon concentrations. Furthermore, the detection limits and uncertainties were evaluated to discuss the characteristics of this method. Key parameters for improving the determination of thoron and radon emanations were found to be the background radon concentration and the leakage of radon from the measurement system, respectively. It was concluded that the present method is advantageous to a sample that has much higher "2"2"6Ra activity than "2"2"4Ra. - Highlights: • The methodology of appropriate and discriminative measurement of thoron and radon emanation is presented. • Measurement of thoron and radon emanated from a sample was made using a scintillation cell. • Detection limits and

  15. Physical and chemical properties of bentonite as backfill and sealing material in a final repository of radioactive wastes. A literature study

    International Nuclear Information System (INIS)

    Schmidt, W.; Kessler, J.; Sitz, P.

    1992-11-01

    Results of a literature study concerning the properties and the changes in properties of bentonite backfill are presented on the basis of current concepts envisaged for final disposal of radioactive waste in Switzerland. The literature preferentially used in this study is that of NAGRA, international papers and special publications from universities in Germany, Austria and Switzerland. Mechanical, physico-mineralogical and chemical properties of bentonite and bentonite-water systems are considered as the central point, particularly taking into account the types MX-80 and Montigel which are favoured in the Swiss concept. Technological problems associated with radioactive waste disposal are only touched on or are taken as being understood. Special attention is paid to considering mutual interactions between different complexes of properties, considering certain aspects of longevity and long-term stability, the discussion is focused on potential physical and chemical impacts of the bentonite backfill. Further investigations should consider the interrelations between mechanical and physical properties, diffusion properties and the influence on bentonite of higher temperatures, of water vapor, of iron corrosion products and of the products of interactions in the water-concrete system. (author) figs., tabs., refs

  16. The response of dense dry granular material to the shear reversal

    Science.gov (United States)

    Zhang, Jie; Ren, Jie; Farhadi, Somayeh; Behringer, Robert

    2008-11-01

    We have performed two dimensional granular experiments under pure shear using bidisperse photo-elastic disks. Starting from a stress free state, a square box filled with granular particles is subject to shear. The forward shears involved various number of steps, leading to maximum strains between 0.1 and 0.3. The area is kept constant during the shear. The network of force chains gradually built up as the strain increased, leading to increased pressure and shear stress. Reverse shear was then applied to the system. Depending on the initial packing fraction and the strain at which the shear is reversed, the force chain network built prior to the shear reversal may be destroyed completely or partially destroyed. Following the force chain weakening, when the reserve shear is continuously applied to the system, there is a force chain strengthening. Following each change of the system, contact forces of individual disks were measured by applying an inverse algorithm. We also kept track of the displacement and angle of rotation of every particle from frame to frame. We present the results for the structure failure and reconstruction during shear reversals. We also present data for stresses, contact force distributions and other statistical measures.

  17. Physical Explanation of Archie's Porosity Exponent in Granular Materials: A Process-Based, Pore-Scale Numerical Study

    Science.gov (United States)

    Niu, Qifei; Zhang, Chi

    2018-02-01

    The empirical Archie's law has been widely used in geosciences and engineering to explain the measured electrical resistivity of many geological materials, but its physical basis has not been fully understood yet. In this study, we use a pore-scale numerical approach combining discrete element-finite difference methods to study Archie's porosity exponent m of granular materials over a wide porosity range. Numerical results reveal that at dilute states (e.g., porosity ϕ > 65%), m is exclusively related to the particle shape and orientation. As the porosity decreases, the electric flow in pore space concentrates progressively near particle contacts and m increases continuously in response to the intensified nonuniformity of the local electrical field. It is also found that the increase in m is universally correlated with the volume fraction of pore throats for all the samples regardless of their particle shapes, particle size range, and porosities.

  18. Gas migration characteristics of highly compacted bentonite ore

    International Nuclear Information System (INIS)

    Tanaka, Yukihisa; Hironaga, Michihiko

    2010-01-01

    In the current concept of repository for radioactive waste disposal, compacted bentonite will be used as an engineered barrier mainly for inhibiting migration of radioactive nuclides. Hydrogen gas can be generated inside the engineered barrier by anaerobic corrosion of metals used for containers, etc. If the gas generation rate exceeds the diffusion rate of dissolved gas inside of the engineered barrier, gas will accumulate in the void space inside of the engineered barrier until its pressure becomes large enough for it to enter the bentonite as a discrete gaseous phase. It is expected to be not easy for gas to entering into the bentonite as a discrete gaseous phase because the pore of compacted bentonite is so minute. Gas migration characteristics of highly compacted powdered bentonite are already reported by CRIEPI. In this report, gas migration characteristics of bentonite ore, which is a candidate for construction material of repository for radioactive waste, is investigated. The following conclusions are obtained through the results of the gas migration tests which are conducted in this study: 1) When the total gas pressure exceeds the initial total axial stress, the total axial stress is always equal to the total gas pressure because specimens shrink in the axial direction with causing the clearance between the end of the specimen and porous metal. By increasing the gas pressure more, gas breakthrough, which defined as a sudden and sharp increase in gas flow rate out of the specimen, occurs. Therefore gas migration mechanism of compacted bentonite ore is basically identical to that of compacted powdered bentonite. 2) Hydraulic conductivity measured after the gas breakthrough is somewhat smaller than that measured before the gas migration test. This fact means that it might be possible to neglect decline of the function of bentonite as engineered barrier caused by the gas breakthrough. These characteristics of compacted bentonite ore are identical to those of

  19. Comparative Analysis on Chemical Composition of Bentonite Clays ...

    African Journals Online (AJOL)

    2017-09-12

    Sep 12, 2017 ... Comparative Analysis on Chemical Composition of Bentonite Clays. Obtained from Ashaka and ... versatile material for geotechnical engineering and as well as their demand for ..... A PhD thesis submitted to the Chemical ...

  20. Bentonite erosion by dilute waters in initially saturated bentonite

    International Nuclear Information System (INIS)

    Olin, Markus; Seppaelae, Anniina; Laurila, Teemu; Koskinen, Kari

    2012-01-01

    Document available in extended abstract form only. One scenario of interest for the long-term safety assessment of a spent nuclear fuel repository involves the loss of bentonite buffer material through contact with dilute groundwater at a transmissive fracture interface (SKB 2011, Posiva 2012a). The scenario is based on the stable colloids at low ionic strength: - the cohesive forces of bentonite decrease in low-salinity conditions, and colloids start to dominate and are able to leave the gel-like bentonite on the groundwater bentonite boundary; - after colloid formation, groundwater may carry away the only just released clay colloids; - low-salinity events are most probable during post-glacial conditions, when also pressure gradients are high, causing elevated flow velocity, which may enhance colloidal transport. Therefore, it is very important from the point of view of repository safety assessment to be able to estimate how much bentonite may be lost during a post-glacial event, when the groundwater salinity and velocity, as well as the duration of the event are fixed. It is possible that more than one event will hit the same canister and buffer, and that several canisters and buffers may be jeopardized. The results in the issue so far may be divided into modelling attempts and experimental work. The modelling has been based on two main guidelines: external (Birgersson et al., 2009) and internal friction models (Neretnieks et al., 2009). However, these models have not been validated for erosion, probably due to lack of suitable laboratory data. The latter approach is more ambitious due to lack of fitting parameters, though the internal friction model itself may be varied. The internal friction model has proven to be time-consuming to solve numerically. This work indicates that experiments carried out by Schatz et al. (2012) differ significantly from the predictions obtained from Neretnieks' model. We present our numerical modelling results based on a set of

  1. Effect of dry density and temperature on the hydraulic conductivity of domestic compacted bentonite as a buffer material in the high level waste repository

    International Nuclear Information System (INIS)

    Cho, Won Jin; Chun, Kwan Sik; Lee, Jae Owan

    1999-02-01

    This study is intended to investigate the effect of dry density and temperature on the hydraulic conductivity of domestic calcium bentonite. The dry densities of bentonite are 1.4 Mg/m 3 , 1.6 Mg/m 3 and 1.6 Mg/m, and the temperatures are in the range of 20 dg C to 150 dg C. The hydraulic conductivities of compacted bentonite with dry densities higher than 1.4 Mg/m 3 are lower than 10 -1 1 m/s, and are low enough to inhibit the radionuclide release by advection through the buffer. The hydraulic conductivities at the temperature of 150 dg C increase up to about 1 order higher than those at 20 dg C. (author). 28 refs., 5 tabs., 20 figs

  2. Porewater chemistry in compacted bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Muurinen, A.; Lehikoinen, J. [VTT Chemical Technology, Espoo (Finland)

    1999-03-01

    In this study, the porewater chemistry in compacted bentonite, considered as an engineered barrier in the repository of spent fuel, has been studied in interaction experiments. Many parameters, like the composition and density of bentonite, composition of the solution, bentonite-to-water ratio (B/W), surrounding conditions and experimental time have been varied in the experiments. At the end of the interaction the equilibrating solution, the porewaters squeezed out of the bentonite samples, and bentonites themselves were analyzed to give information for the interpretation and modelling of the interaction. Equilibrium modelling was performed with the HYDRAQL/CE computer code 33 refs.

  3. Incorporating Zataria multiflora Boiss. essential oil and sodium bentonite nano-clay open a new perspective to use zein films as bioactive packaging materials.

    Science.gov (United States)

    Kashiri, Mahboobeh; Maghsoudlo, Yahya; Khomeiri, Morteza

    2017-10-01

    Active zein films with different levels of Zataria multiflora Boiss. essential oil were produced successfully. To enhance properties of this biopolymer for food packaging applications, sodium bentonite clay was used at two levels (2 and 4%). The results indicated that the addition of Z. multiflora Boiss. essential oil caused a reduction in tensile strength and Young's modulus and slight increase in the percent of elongation at break of the films. Maximum solubility in water and water vapor permeability was observed by incorporation of 10% Z. multiflora Boiss. essential oil in the zein matrix. Transmission electron microscopy micrographs of zein film were verified by the exfoliation of the layers of sodium bentonite clay in the zein matrix. Stronger films with lower water vapor permeability and water solubility were evident of good distribution of sodium bentonite clay in the zein matrix. According to the results, 2% sodium bentonite clay was selected for evaluation of nano active film properties. Water vapor permeability, UV light barrier, tensile strength, and Young's modulus values of active films were improved by incorporation of 2% sodium bentonite clay. The antibacterial activity of different contents of Z. multiflora Boiss. essential oil in vapor phase demonstrated that use of Z. multiflora Boiss. essential oil in the liquid phase was more effective than in vapor phase. The antibacterial zein-based films showed that active zein film with 5 and 10% Z. multiflora Boiss. essential oil had reductions of 1.68 log and 2.99 log, respectively, against Listeria monocytogenes and 1.39 and 3.07 log against Escherichia coli. Nano active zein film containing 10% Z. multiflora Boiss. essential oil and 2% sodium bentonite clay showed better antibacterial properties against L. monocytogenes (3.23 log) and E. coli (3.17 log).

  4. COMPORTAMIENTO DE UN MATERIAL GRANULAR NO TRATADO EN ENSAYOS TRIAXIALES CÍCLICOS CON PRESIÓN DE CONFINAMIENTO CONSTANTE Y VARIABLE BEHAVIOR OF AN UNBOUND GRANULAR MATERIAL IN CYCLIC TRIAXIAL TESTS WITH CONSTANT AND VARIABLE CONFINING PRESSURE

    Directory of Open Access Journals (Sweden)

    Hugo Alexander Rondón Quintana

    2008-12-01

    Full Text Available En un pavimento, cada una de las capas de la estructura experimenta bajo una carga vehicular ciclos de esfuerzo con componentes vertical, horizontal y de corte. Para el estudio de materiales granulares no tratados (utilizados para conformar capas de base y subbase, la mayor parte de las investigaciones se realizan empleando equipos triaxiales cíclicos en donde sólo la carga vertical es cíclica y la presión de confinamiento permanece constante durante el ensayo. Un ensayo que reproduce mejor la forma como se distribuyen los esfuerzos en estas capas es el ensayo triaxial cíclico con presión de confinamiento variable. En este ensayo se pueden modelar las componentes cíclicas tanto en el sentido vertical como horizontal. A pesar que son ensayos distintos, la ingeniería de pavimentos supone que la respuesta que experimentan estos materiales en estos ensayos es similar, lo anterior basado en algunos estudios realizados en la década de los setenta. En la presente investigación se diseña y desarrolla un programa experimental más detallado, para comparar el comportamiento que desarrolla un material granular no tratado en estos ensayos. De los resultados se evidencia que sólo para algunas trayectorias de esfuerzo, la dirección y la acumulación de la deformación vertical y volumétrica es similar.In a pavement structure, passing wheel loads impose cyclic stresses consisting of vertical, horizontal and shear components. Studies of the behavior of unbound granular materials (UGM, used for base and sub-base layers under cyclic loading are mostly performed using the axisymmetric triaxial test with constant confining pressure (CCP test and a cyclic variation of the axial stress. However, in this type of test only the vertical component of the cyclic stress path is considered. The oscillation of the horizontal stress can be reproduced by an additional cyclic variation of the confining pressure (VCP test. CCP and VCP tests are sometimes assumed to

  5. Reactive transport modelling of groundwater-bentonite interaction: Effects on exchangeable cations in an alternative buffer material in-situ test

    International Nuclear Information System (INIS)

    Wallis, I.; Idiart, A.; Dohrmann, R.; Post, V.

    2016-01-01

    Bentonite clays are regarded a promising material for engineered barrier systems for the encapsulation of hazardous wastes because of their low hydraulic permeability, swelling potential, ability to self-seal cracks in contact with water and their high sorption potential. SKB (Svensk Kärnbränslehantering) has been conducting long term field scale experiments on potential buffer materials at the Äspö Hard Rock Laboratory for radioactive waste disposal in Sweden. The Alternative Buffer Material (ABM) test examined buffer properties of eleven different clay materials under the influence of groundwater and at temperatures reaching up to 135 °C, replicating the heat pulse after waste emplacement. Clay materials were emplaced into holes drilled in fractured granite as compacted rings around a central heater element and subsequently brought into contact with groundwater for 880 days. After test termination, and against expectations, all clay materials were found to have undergone large scale alterations in the cation exchange population. A reactive-diffusive transport model was developed to aid the interpretation of the observed large-scale porewater chemistry changes. It was found, that the interaction between Äspö groundwater and the clay blocks, together with the geochemical nature of the clays (Na vs Ca-dominated clays) exerted the strongest control on the porewater chemistry. A pronounced exchange of Na by Ca was observed and simulated, driven by large Ca concentrations in the contacting groundwater. The model was able to link the porewater alterations to the fracture network in the deposition hole. The speed of alterations was in turn linked to high diffusion coefficients under the applied temperatures, which facilitated the propagation of hydrochemical changes into the clays. With diffusion coefficients increased by up to one order of magnitude at the maximum temperatures, the study was able to demonstrate the importance of considering temperature

  6. Quasi-static incremental behavior of granular materials: Elastic-plastic coupling and micro-scale dissipation

    Science.gov (United States)

    Kuhn, Matthew R.; Daouadji, Ali

    2018-05-01

    The paper addresses a common assumption of elastoplastic modeling: that the recoverable, elastic strain increment is unaffected by alterations of the elastic moduli that accompany loading. This assumption is found to be false for a granular material, and discrete element (DEM) simulations demonstrate that granular materials are coupled materials at both micro- and macro-scales. Elasto-plastic coupling at the macro-scale is placed in the context of thermomechanics framework of Tomasz Hueckel and Hans Ziegler, in which the elastic moduli are altered by irreversible processes during loading. This complex behavior is explored for multi-directional loading probes that follow an initial monotonic loading. An advanced DEM model is used in the study, with non-convex non-spherical particles and two different contact models: a conventional linear-frictional model and an exact implementation of the Hertz-like Cattaneo-Mindlin model. Orthotropic true-triaxial probes were used in the study (i.e., no direct shear strain), with tiny strain increments of 2 ×10-6 . At the micro-scale, contact movements were monitored during small increments of loading and load-reversal, and results show that these movements are not reversed by a reversal of strain direction, and some contacts that were sliding during a loading increment continue to slide during reversal. The probes show that the coupled part of a strain increment, the difference between the recoverable (elastic) increment and its reversible part, must be considered when partitioning strain increments into elastic and plastic parts. Small increments of irreversible (and plastic) strain and contact slipping and frictional dissipation occur for all directions of loading, and an elastic domain, if it exists at all, is smaller than the strain increment used in the simulations.

  7. Comparisons of physical experiment and discrete element simulations of sheared granular materials in an annular shear cell

    Science.gov (United States)

    Ji, S.; Hanes, D.M.; Shen, H.H.

    2009-01-01

    In this study, we report a direct comparison between a physical test and a computer simulation of rapidly sheared granular materials. An annular shear cell experiment was conducted. All parameters were kept the same between the physical and the computational systems to the extent possible. Artificially softened particles were used in the simulation to reduce the computational time to a manageable level. Sensitivity study on the particle stiffness ensured such artificial modification was acceptable. In the experiment, a range of normal stress was applied to a given amount of particles sheared in an annular trough with a range of controlled shear speed. Two types of particles, glass and Delrin, were used in the experiment. Qualitatively, the required torque to shear the materials under different rotational speed compared well with those in the physical experiments for both the glass and the Delrin particles. However, the quantitative discrepancies between the measured and simulated shear stresses were nearly a factor of two. Boundary conditions, particle size distribution, particle damping and friction, including a sliding and rolling, contact force model, were examined to determine their effects on the computational results. It was found that of the above, the rolling friction between particles had the most significant effect on the macro stress level. This study shows that discrete element simulation is a viable method for engineering design for granular material systems. Particle level information is needed to properly conduct these simulations. However, not all particle level information is equally important in the study regime. Rolling friction, which is not commonly considered in many discrete element models, appears to play an important role. ?? 2009 Elsevier Ltd.

  8. Discrete Element Method for Modeling the Mechanical Behavior of Unsaturated Granular Material

    Directory of Open Access Journals (Sweden)

    K. Tourani

    2016-09-01

    Full Text Available Although a significant portion of conditions encountered in geotechnical engineering, for investigating engineering behavior of soil, involves unsaturated soils; the traditional analysis and design approach has been to assume the limiting conditions of soils being either completely dry or completely saturated. In unsaturated soils the capillary force produce attractive forces between particles. Discrete Element Method (DEM is an appropriate tool to consider the capillary effects. The calculations performed in DEM is based on iterative application of Newton’s second law to the particles and force-displacement law at the contacts. In the present study, the behavior of unsaturated soils in pendular regime is simulated utilizing DEM. Triaxial  compression tests were modeled as two-dimensional, considering capillary force effects. Finally, capillary effects on Macro parameters of a simulated granular soil (stress, axial strain, volumetric strain and void ratio and Mohr Coulomb failure criteria parameters were studied.

  9. Torsional shear flow of granular materials: shear localization and minimum energy principle

    Science.gov (United States)

    Artoni, Riccardo; Richard, Patrick

    2018-01-01

    The rheological properties of granular matter submitted to torsional shear are investigated numerically by means of discrete element method. The shear cell is made of a cylinder filled by grains which are sheared by a bumpy bottom and submitted to a vertical pressure which is applied at the top. Regimes differing by their strain localization features are observed. They originate from the competition between dissipation at the sidewalls and dissipation in the bulk of the system. The effects of the (i) the applied pressure, (ii) sidewall friction, and (iii) angular velocity are investigated. A model, based on the purely local μ (I)-rheology and a minimum energy principle is able to capture the effect of the two former quantities but unable to account the effect of the latter. Although, an ad hoc modification of the model allows to reproduce all the numerical results, our results point out the need for an alternative rheology.

  10. Formula of Moulding Sand, Bentonite and Portland Cement toImprove The Quality of Al-Si Cast Alloy

    OpenAIRE

    Andoko Andoko; Poppy Puspitasari; Avita Ayu Permanasari; Didin Zakaria Lubis

    2017-01-01

    A binder is any material used to strengthen the bonding of moulding sand grains. The primary function of the binder is to hold the moulding sand and other materialstogether to produce high-quality casts. In this study, there were four binder compositions being tested, i.e. 5% bentonite + 5% Portland cement, 4% bentonite + 6% Portland cement, 6% bentonite + 4% Portland cement, and 7% bentonite + 3% Portland cement. Each specimen was measured for its compressive strength, shear strength, tensil...

  11. Strength and Compaction Analysis of Sand-Bentonite-Coal Ash Mixes

    Science.gov (United States)

    Sobti, Jaskiran; Singh, Sanjay Kumar

    2017-08-01

    This paper deals with the strength and compaction characteristics of sand-bentonite-coal ash mixes prepared by varying percentages of sand, bentonite and coal ash to be used in cutoff walls and as a liner or cover material in landfills. The maximum dry density (MDD) and optimum moisture content (OMC) of sand-bentonite mixes and sand-bentonite-coal ash mixes were determined by conducting the standard proctor test. Also, the strength and stiffness characteristics of soil mixes were furnished using unconfined compressive strength test. The results of the study reveal influence of varying percentages of coal ash and bentonite on the compaction characteristics of the sand-bentonite-coal ash mixes. Also, validation of a statistical analysis of the correlations between maximum dry density (MDD), optimum moisture content (OMC) and Specific Gravity (G) was done using the experimental results. The experimental results obtained for sand-bentonite, sand-bentonite-ash and coal ash-bentonite mixes very well satisfied the statistical relations between MDD, OMC and G with a maximum error in the estimate of MDD being within ±1 kN/m3. The coefficient of determination (R2) ranged from 0.95 to 0.967 in case of sand-bentonite-ash mixes. However, for sand-bentonite mixes, the R2 values are low and varied from 0.48 to 0.56.

  12. Percolation-induced plasmonic state and double negative electromagnetic properties of Ni-Zn Ferrite/Cu granular composite materials

    Science.gov (United States)

    Massango, Herieta; Kono, Koji; Tsutaoka, Takanori; Kasagi, Teruhiro; Yamamoto, Shinichiro; Hatakeyama, Kenichi

    2018-05-01

    Complex permeability and permittivity spectra of Ni-Zn Ferrite/Cu hybrid granular composite materials have been studied in the RF to microwave frequency range. The electrical conductivity σ shows insulating properties in the volume fraction of Cu particles below φ = 0.14. A large jump in conductivity was observed between φ = 0.14 and 0.24 indicating that the Cu particles make metallic conduction between this interval. Hence, the percolation threshold φC, was estimated to be 0.14. A percolation-induced low frequency plasmonic state with negative permittivity spectrum was observed from φ = 0.14-0.24. Meanwhile the negative permeability was observed at φ = 0.16, 0.19 and 0.24. Hence the DNG characteristic was realized in these Cu volume content in the frequency range from 105 MHz to 2 GHz.

  13. Capillary pressure-saturation relationships for porous granular materials: Pore morphology method vs. pore unit assembly method

    Science.gov (United States)

    Sweijen, Thomas; Aslannejad, Hamed; Hassanizadeh, S. Majid

    2017-09-01

    In studies of two-phase flow in complex porous media it is often desirable to have an estimation of the capillary pressure-saturation curve prior to measurements. Therefore, we compare in this research the capability of three pore-scale approaches in reproducing experimentally measured capillary pressure-saturation curves. To do so, we have generated 12 packings of spheres that are representative of four different glass-bead packings and eight different sand packings, for which we have found experimental data on the capillary pressure-saturation curve in the literature. In generating the packings, we matched the particle size distributions and porosity values of the granular materials. We have used three different pore-scale approaches for generating the capillary pressure-saturation curves of each packing: i) the Pore Unit Assembly (PUA) method in combination with the Mayer and Stowe-Princen (MS-P) approximation for estimating the entry pressures of pore throats, ii) the PUA method in combination with the hemisphere approximation, and iii) the Pore Morphology Method (PMM) in combination with the hemisphere approximation. The three approaches were also used to produce capillary pressure-saturation curves for the coating layer of paper, used in inkjet printing. Curves for such layers are extremely difficult to determine experimentally, due to their very small thickness and the presence of extremely small pores (less than one micrometer in size). Results indicate that the PMM and PUA-hemisphere method give similar capillary pressure-saturation curves, because both methods rely on a hemisphere to represent the air-water interface. The ability of the hemisphere approximation and the MS-P approximation to reproduce correct capillary pressure seems to depend on the type of particle size distribution, with the hemisphere approximation working well for narrowly distributed granular materials.

  14. Dynamic induced softening in frictional granular materials investigated by discrete-element-method simulation

    Science.gov (United States)

    Lemrich, Laure; Carmeliet, Jan; Johnson, Paul A.; Guyer, Robert; Jia, Xiaoping

    2017-12-01

    A granular system composed of frictional glass beads is simulated using the discrete element method. The intergrain forces are based on the Hertz contact law in the normal direction with frictional tangential force. The damping due to collision is also accounted for. Systems are loaded at various stresses and their quasistatic elastic moduli are characterized. Each system is subjected to an extensive dynamic testing protocol by measuring the resonant response to a broad range of ac drive amplitudes and frequencies via a set of diagnostic strains. The system, linear at small ac drive amplitudes, has resonance frequencies that shift downward (i.e., modulus softening) with increased ac drive amplitude. Detailed testing shows that the slipping contact ratio does not contribute significantly to this dynamic modulus softening, but the coordination number is strongly correlated to this reduction. This suggests that the softening arises from the extended structural change via break and remake of contacts during the rearrangement of bead positions driven by the ac amplitude.

  15. The Grading Entropy-based Criteria for Structural Stability of Granular Materials and Filters

    Directory of Open Access Journals (Sweden)

    Janos Lőrincz

    2015-05-01

    Full Text Available This paper deals with three grading entropy-based rules that describe different soil structure stability phenomena: an internal stability rule, a filtering rule and a segregation rule. These rules are elaborated on the basis of a large amount of laboratory testing and from existing knowledge in the field. Use is made of the theory of grading entropy to derive parameters which incorporate all of the information of the grading curve into a pair of entropy-based parameters that allow soils with common behaviours to be grouped into domains on an entropy diagram. Applications of the derived entropy-based rules are presented by examining the reason of a dam failure, by testing against the existing filter rules from the literature, and by giving some examples for the design of non-segregating grading curves (discrete particle size distributions by dry weight. A physical basis for the internal stability rule is established, wherein the higher values of base entropy required for granular stability are shown to reflect the closeness between the mean and maximum grain diameters, which explains how there are sufficient coarser grains to achieve a stable grain skeleton.

  16. The Quantified Characterization Method of the Micro-Macro Contacts of Three-Dimensional Granular Materials on the Basis of Graph Theory.

    Science.gov (United States)

    Guan, Yanpeng; Wang, Enzhi; Liu, Xiaoli; Wang, Sijing; Luan, Hebing

    2017-08-03

    We have attempted a multiscale and quantified characterization method of the contact in three-dimensional granular material made of spherical particles, particularly in cemented granular material. Particle contact is defined as a type of surface contact with voids in its surroundings, rather than a point contact. Macro contact is a particle contact set satisfying the restrictive condition of a two-dimensional manifold with a boundary. On the basis of graph theory, two dual geometrical systems are abstracted from the granular pack. The face and the face set, which satisfies the two-dimensional manifold with a boundary in the solid cell system, are extracted to characterize the particle contact and the macro contact, respectively. This characterization method is utilized to improve the post-processing in DEM (Discrete Element Method) from a micro perspective to describe the macro effect of the cemented granular material made of spherical particles. Since the crack has the same shape as its corresponding contact, this method is adopted to characterize the crack and realize its visualization. The integral failure route of the sample can be determined by a graph theory algorithm. The contact force is assigned to the weight value of the face characterizing the particle contact. Since the force vectors can be added, the macro contact force can be solved by adding the weight of its corresponding faces.

  17. Scientific Opinion on the safety evaluation of the active substances, sodium carbonate peroxyhydrate coated with sodium carbonate and sodium silicate, bentonite, sodium chloride, sodium carbonate for use in active food contact materials

    OpenAIRE

    EFSA Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids (CEF)

    2013-01-01

    This scientific opinion of the Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids deals with the safety evaluation of the powder mixture of the active substances sodium carbonate peroxyhydrate coated with sodium carbonate and sodium silicate (FCM substance No 1009), bentonite (CAS No 1302-78-9, FCM No 393), sodium chloride (CAS No 7647-14-5, FCM No 985), sodium carbonate (CAS No 497-19-8, FCM No 1008) which are intended to be used as combined oxygen generator and carbon...

  18. Frequency Methods Applied to the Characterization of the Thermophysical Properties of a Granular Material with a Cylindrical Probe

    Science.gov (United States)

    Carpentier, Olivier; Defer, Didier; Antczak, Emmanuel; Chartier, Thierry

    2012-01-01

    In many fields, such as in the agri-food industry or in the building industry, it is important to be able to monitor the thermophysical properties of granular materials. Regular thermal probes allow for the determination of one or several thermophysical factors. The success of the method used depends in part on the nature of the signal sent, on the type of physical model applied and eventually on the type of probe used and its implantation in the material. Although efficacious for most applications, regular thermal probes do present some limitations. It is the case, for example, when one has to know precisely the thermal contact resistance or the nature of the signal sent. In this article is presented a characterization method based on thermal impedance formalism. This method allows for the determination of the thermal conductivity, the thermal diffusivity, and the contact thermal resistance in one single test. The application of this method requires the use of a specific probe developed to enable measurement of heat flux and temperature at the interface of the probe and the studied material. Its practical application is presented for dry sand.

  19. Relationship between dilatancy, stresses and plastic dissipation in a granular material with rigid grains

    Science.gov (United States)

    Evesque, Pierre; Stefani, Christian

    1991-11-01

    By considering a drained cohesionless granular sample made up of rigid grains and submitted to a triaxial test, we derive an equation relating the dilatancy K, the deviatoric stress q and the confining pressure p to the energy losses D_plastic due to plastic yielding. We demonstrate that the system is contracting (K le 0) at q = 0, when q is increasing and that spontaneous uncontrolled yielding begins occurring when dilatancy K is maximum. We also demonstrate the existence of the characteristic state introduced by Luong and Habib and the existence of the critical state of Schofield and Wroth. Finally, we give a method to determine the plastic losses during a triaxial cell test using the experimental data. En utilisant un postulat de reproductibilité des essais triaxiaux et une relation liant l'énergie dissipée, la dilatance K et les contraintes imposées à un échantillon, on démontre qu'un matériau granulaire ne peut que se contracter après avoir subi une contrainte de confinement isotrope (i.e. q = 0), que la rupture spontanée a lieu après un maximum de dilatance, qu'il existe un état caractéristique (au sens de Luong et Habib) et qu'il existe un état “ critique ” (au sens de Schofield et Wroth). Nous donnons de plus une méthode pour estimer la dissipation-plastique durant un essai triaxial à partir des résultats expérimentaux.

  20. Granular boycott effect: How to mix granulates

    Science.gov (United States)

    Duran, J.; Mazozi, T.

    1999-11-01

    Granular material can display the basic features of the Boycott effect in sedimentation. A simple experiment shows that granular material falls faster in an inclined tube than in a vertical tube, in analogy with the Boycott effect. As long as the inclination of the tube is above the avalanche threshold, descent of granular material in the tube causes internal convection which in turn results in an efficient mixture of the granular components. By contrast, as in analogous experiments in two dimensions, a vertical fall of granular material occurs via successive block fragmentation, resulting in poor mixing.

  1. Thermal characteristics of highly compressed bentonite

    International Nuclear Information System (INIS)

    Sueoka, Tooru; Kobayashi, Atsushi; Imamura, S.; Ogawa, Terushige; Murata, Shigemi.

    1990-01-01

    In the disposal of high level radioactive wastes in strata, it is planned to protect the canisters enclosing wastes with buffer materials such as overpacks and clay, therefore, the examination of artificial barrier materials is an important problem. The concept of the disposal in strata and the soil mechanics characteristics of highly compressed bentonite as an artificial barrier material were already reported. In this study, the basic experiment on the thermal characteristics of highly compressed bentonite was carried out, therefore, it is reported. The thermal conductivity of buffer materials is important because the possibility that it determines the temperature of solidified bodies and canisters is high, and the buffer materials may cause the thermal degeneration due to high temperature. Thermophysical properties are roughly divided into thermodynamic property, transport property and optical property. The basic principle of measured thermal conductivity and thermal diffusivity, the kinds of the measuring method and so on are explained. As for the measurement of the thermal conductivity of highly compressed bentonite, the experimental setup, the procedure, samples and the results are reported. (K.I.)

  2. Granular model, percolation-resistivity, ESR and elastic modulus of carbonaceous materials application to the babassu endocarp heat treated up to 22000C

    International Nuclear Information System (INIS)

    Emmerich, F.G.

    1987-01-01

    A microscopic model (granular model) is presented to study heat treated carbons. A granular structure is defined in the carbon matrix, composed of turbostratic graphite-like microcrystallites, cross-linkings and micropores. A general expression is developed to calculate the volume fraction X of the conducting phase of the granular structure as a function of structural parameters obtained from X-ray diffraction small angle X-ray scattering. The granular model and the percolation theory are used to explain the electrical resistivity behaviour with the heat treatment temperature (HTT), where X is the fundamental parameter. An electron spin resonance (ESR) study of the low and high HTT ranges is presented, including the transition range (700-1300 0 C). The elucitation of the spin center nature in this range and the liking with the two adjacent ranges has been pursued. An expression to calculate the elastic modulus (Young's modulus), based on the microscopic granular model with the fundamental participation of the cross-linkings, is derived to account for the behavior of the modulus with the HTT. The granular model with the expression of X, the percolation-resistivity theory, the ESR study, and the expression of the elastic modulus are applied to the babassu endocarp carbon heat treated up to 2200 0 C. This material can be classified as a tipical non-graphitic carbon, being useful to search the validity of the model and the proposed expressions. It is observed that the theoretical expressions describe with reasonable accuracy the respective experimental behaviours. The measurements of physical and chemical parameters of the babassu endocarp treated up to 2200 0 C area also included. (author) [pt

  3. Bentonite erosion. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Birgersson, Martin; Boergesson, Lennart; Hedstroem, Magnus; Karnland, Ola; Nilsson, Ulf (Clay Technology AB, Lund (Sweden))

    2009-12-15

    Low saline water may reach KBS-3 repository depth, e.g. during periods of glaciation. Under such aqueous conditions, the montmorillonite part of the bentonite buffer might transform into a sol and thereby be transported away with flowing water in fractures. The primary aim with this report is to improve the understanding of the basic principles for this possible montmorillonite particle release. The report includes experimental and theoretical work performed at Clay Technology. Natural bentonite and ion-exchanged purified montmorillonite from three different geographical origins, Wyoming (U.S.), Milos (Greece) and Kutch (India) have been studied. Experimental and/or theoretical investigations have been performed with respect to: - Free swelling ability; - Rheological properties; - Rate of bentonite loss into fractures; - Filtering; - Ion exchange; - Sol formation ability; - Ion diffusion; - Mass loss due to erosion. The performed erosion experiments show that erosion does not occur in a mixed calcium/sodium montmorillonite with at least 20% calcium in exchange positions, when the external solution contains above 4 mM charge equivalents. This result is in agreement with the presented conceptual view of sol formation and measured equilibrium properties in mixed calcium/sodium montmorillonite. The findings imply that the buffer will be stable for non-glacial conditions. However, erosion due to sol formation cannot be ruled out for glacial conditions.

  4. Bentonite erosion. Final report

    International Nuclear Information System (INIS)

    Birgersson, Martin; Boergesson, Lennart; Hedstroem, Magnus; Karnland, Ola; Nilsson, Ulf

    2009-12-01

    Low saline water may reach KBS-3 repository depth, e.g. during periods of glaciation. Under such aqueous conditions, the montmorillonite part of the bentonite buffer might transform into a sol and thereby be transported away with flowing water in fractures. The primary aim with this report is to improve the understanding of the basic principles for this possible montmorillonite particle release. The report includes experimental and theoretical work performed at Clay Technology. Natural bentonite and ion-exchanged purified montmorillonite from three different geographical origins, Wyoming (U.S.), Milos (Greece) and Kutch (India) have been studied. Experimental and/or theoretical investigations have been performed with respect to: - Free swelling ability; - Rheological properties; - Rate of bentonite loss into fractures; - Filtering; - Ion exchange; - Sol formation ability; - Ion diffusion; - Mass loss due to erosion. The performed erosion experiments show that erosion does not occur in a mixed calcium/sodium montmorillonite with at least 20% calcium in exchange positions, when the external solution contains above 4 mM charge equivalents. This result is in agreement with the presented conceptual view of sol formation and measured equilibrium properties in mixed calcium/sodium montmorillonite. The findings imply that the buffer will be stable for non-glacial conditions. However, erosion due to sol formation cannot be ruled out for glacial conditions.

  5. Reduction of intergranular exchange coupling and grain size for high Ku CoPt-based granular media: Metal-oxide buffer layer and multiple oxide boundary materials

    Directory of Open Access Journals (Sweden)

    Kim Kong Tham

    2018-05-01

    Full Text Available Investigation of magnetic properties and microstructure of granular media with various multiple oxides as the grain boundary material is reported. Saturation magnetization (Ms, uniaxial magnetocrystalline anisotropy (Ku, and magnetic grain diameter (GD of the granular media show linear correlation with volume weighted average for melting point (Tm of each oxides (Tmave. Ku of magnetic grains (Kugrain shows a trade-off relation with GD that it is a big challenge to satisfy both high Kugrain and small GD by only controlling Tmave. To obtain a granular medium with appropriate Kugrain, GD, and low degree of intergranular exchange coupling, the combination of Tmave control of grain boundary material by mixing oxides and employment of a buffer layer are required. Here the degree of intergranular exchange coupling is estimated from the slope of M-H loop at around coercivity (α. By applying this technique, a typical granular medium with Kugrain of 1.0×107 erg/cm3, GD of 5.1 nm, and α of 1.2 is realized.

  6. Reduction of intergranular exchange coupling and grain size for high Ku CoPt-based granular media: Metal-oxide buffer layer and multiple oxide boundary materials

    Science.gov (United States)

    Tham, Kim Kong; Kushibiki, Ryosuke; Kamada, Tomonari; Hinata, Shintaro; Saito, Shin

    2018-05-01

    Investigation of magnetic properties and microstructure of granular media with various multiple oxides as the grain boundary material is reported. Saturation magnetization (Ms), uniaxial magnetocrystalline anisotropy (Ku), and magnetic grain diameter (GD) of the granular media show linear correlation with volume weighted average for melting point (Tm) of each oxides (Tmave). Ku of magnetic grains (Kugrain) shows a trade-off relation with GD that it is a big challenge to satisfy both high Kugrain and small GD by only controlling Tmave. To obtain a granular medium with appropriate Kugrain, GD, and low degree of intergranular exchange coupling, the combination of Tmave control of grain boundary material by mixing oxides and employment of a buffer layer are required. Here the degree of intergranular exchange coupling is estimated from the slope of M-H loop at around coercivity (α). By applying this technique, a typical granular medium with Kugrain of 1.0×107 erg/cm3, GD of 5.1 nm, and α of 1.2 is realized.

  7. Long term mineralogical properties of bentonite/quartz buffer substance

    International Nuclear Information System (INIS)

    Jacobsson, A.; Pusch, R.

    1978-06-01

    This report shows results from investigations concerning properties in bentonitebased buffersubstances which are suggested to be used when high level radioactive wastes from nuclear powerplants are to be stored finally. Recommended material characteristica of the bentonite to be used are summerized. In an attempt to find geological evidence for bentonite to loose its desireable properties there were no such findings at the temperatures, groundwater situations and pressures which are to be expected at the actual depositing depth (500 m) for a considerable period of time. Concerning biological activity and then specially the mobility and activity of bacteria the conclusion is that there will be little or no influence from them either there is bentonite-sand or compacted pure bentonite in the buffer mass

  8. Physico-chemical properties of water in bentonite

    International Nuclear Information System (INIS)

    Torikai, Yuji; Sato, Seichi; Ohashi, Hiroshi

    1994-01-01

    As a part of safety analysis on ground layer disposal, in order to estimate nuclides migration behavior from engineering shielding materials, it is required to modelize migration process of nuclides in bentonite and chemical species relating to corrosion, to estimate solubility and to specify application condition of geochemical calculation code. In this study, as a part of elucidation of nuclide migration process, physico-chemical properties of water in bentonite and montmorillonite using steam pressure method were determined. As a result, following items were found: (1) Even if 1/3 of water in bentonite is near free water, it is far from a region dealable with dilute solution in the electrolyte solution theory. And, (2) the water in bentonite has generally small activity in comparison with dilute solution, then has smaller solubility than estimation value of calculation code. (G.K.)

  9. Polyaniline (PANI) modified bentonite by plasma technique for U(VI) removal from aqueous solution

    International Nuclear Information System (INIS)

    Liu, Xinghao; Cheng, Cheng; Xiao, Chengjian; Shao, Dadong; Xu, Zimu; Wang, Jiaquan; Hu, Shuheng; Li, Xiaolong; Wang, Weijuan

    2017-01-01

    Highlights: • PANI/bentonie can be synthesized by simple plasma technique. • PANI/bentonie has an excellent adsorption capacity for trace uranium in solution. • U(VI) adsorption on PANI/bentonite is a spontaneous and endothermic process. - Abstract: Polyaniline (PANI) modified bentonite (PANI/bentonie) was synthesized by plasma induced polymerization of aniline on bentonite surface, and applied to uptake of uranium(VI) ions from aqueous solution. The as-synthesized PANI/bentonie was characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), thermal gravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). Batch adsorption technique was utilized to investigate the adsorption of U(VI) on bentonite and PANI/bentonite. The adsorption of U(VI) (10 mg/L) on PANI/bentonite surface is fairly depend on solution pH, ionic strength, and temperature in solution. The modified PANI on PANI/bentonite surface significantly enhances its adsorption capability for U(VI). The presence of humic acid (HA) can sound enhance U(VI) adsorption on PANI/bentonite at pH 6.5. According to the thermodynamic parameters, the adsorption of U(VI) on PANI/bentonite surface is a spontaneous and endothermic process. The results highlight the application of PANI/bentonite composites as candidate material for the uptake of trace U(VI) from aqueous solution.

  10. Polyaniline (PANI) modified bentonite by plasma technique for U(VI) removal from aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xinghao [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); Intelligent Manufacturing Technology Research Institute, Hefei University of Technology, Hefei 230088 (China); Cheng, Cheng [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Xiao, Chengjian, E-mail: xiaocj@caep.cn [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); Shao, Dadong, E-mail: shaodadong@126.com [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Xu, Zimu, E-mail: xzm@mail.ustc.edu.cn [Intelligent Manufacturing Technology Research Institute, Hefei University of Technology, Hefei 230088 (China); Wang, Jiaquan; Hu, Shuheng [Intelligent Manufacturing Technology Research Institute, Hefei University of Technology, Hefei 230088 (China); Li, Xiaolong; Wang, Weijuan [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China)

    2017-07-31

    Highlights: • PANI/bentonie can be synthesized by simple plasma technique. • PANI/bentonie has an excellent adsorption capacity for trace uranium in solution. • U(VI) adsorption on PANI/bentonite is a spontaneous and endothermic process. - Abstract: Polyaniline (PANI) modified bentonite (PANI/bentonie) was synthesized by plasma induced polymerization of aniline on bentonite surface, and applied to uptake of uranium(VI) ions from aqueous solution. The as-synthesized PANI/bentonie was characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), thermal gravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). Batch adsorption technique was utilized to investigate the adsorption of U(VI) on bentonite and PANI/bentonite. The adsorption of U(VI) (10 mg/L) on PANI/bentonite surface is fairly depend on solution pH, ionic strength, and temperature in solution. The modified PANI on PANI/bentonite surface significantly enhances its adsorption capability for U(VI). The presence of humic acid (HA) can sound enhance U(VI) adsorption on PANI/bentonite at pH < 6.5 because of the strong complexation, and inhibits U(VI) adsorption at pH > 6.5. According to the thermodynamic parameters, the adsorption of U(VI) on PANI/bentonite surface is a spontaneous and endothermic process. The results highlight the application of PANI/bentonite composites as candidate material for the uptake of trace U(VI) from aqueous solution.

  11. Sequential use of bentonites and solar photocatalysis to treat winery wastewater.

    Science.gov (United States)

    Rodríguez, Eva; Márquez, Gracia; Carpintero, Juan Carlos; Beltrán, Fernando J; Alvarez, Pedro

    2008-12-24

    The sequential use of low-cost adsorbent bentonites and solar photocatalysis to treat winery wastewater has been studied. Three commercial sodium-bentonites (MB-M, MB-G, and MB-P) and one calcium-bentonite (Bengel) were characterized and used in this study. These clay materials were useful to totally remove turbidity (90-100%) and, to a lesser extent, color, polyphenols (PPh), and soluble chemical oxygen demand (CODS) from winery wastewater. Both surface area and cation exchange capacity (CEC) of bentonite had a positive impact on treatment efficiency. The effect of pH on turbidity removal by bentonites was studied in the 3.5-12 pH range. The bentonites were capable of greatly removing turbidity from winery wastewater at pH 3.5-5.5, but removal efficiency decreased with pH increase beyond this range. Settling characteristics (i.e., sludge volume index (SVI) and settling rate) of bentonites were also studied. Best settling properties were observed for bentonite doses around 0.5 g/L. The reuse of bentonite for winery wastewater treatment was found not to be advisable as the turbidity and PPh removal efficiencies decreased with successive uses. The resulting wastewater after bentonite treatment was exposed to solar radiation at oxic conditions in the presence of Fe(III) and Fe(III)/H2O2 catalysts. Significant reductions of COD, total organic carbon (TOC), and PPh were achieved by these solar photocatalytic processes.

  12. The use of Syrian bentonite to remove organics and other ions from commercial Syrian phosphoric acid

    International Nuclear Information System (INIS)

    Khorfan, S.; Abdulbaki, M.; Zein, A.

    2006-01-01

    Using of activated carbon to remove organic matter from phosphoric acid in uranium and P 2 O 5 extraction units has high cost. A new study was conducted to establish a new material instead of activated carbon. Experiments were carried out on removing organic matter by adsorption on Syrian bentonite. The experiments of the removal of humic acid by Syrian bentonite gave good results and showed that the chemical and thermal activation of bentonite increased the adsorption efficiency. (Authors)

  13. The use of Syrian bentonite to remove organics and other ions from commercial Syrian phosphoric acid

    International Nuclear Information System (INIS)

    Khorfan, S.; Abdulbaki, M.; Zein, A.

    2005-03-01

    Using of activated carbon to remove organic matter from phosphoric acid in uranium and P 2 O 5 extraction units has high cost. A new study was conducted to establish a new material instead of activated carbon. Experiments were carried out on removing organic matter by adsorption on Syrian bentonite. The experiments of the removal of humic acid by Syrian bentonite gave good results and showed that the chemical and thermal activation of bentonite increased the adsorption efficiency. (Authors)

  14. Hydrothermal alterations of Bentonites in Almeria (Spain)

    International Nuclear Information System (INIS)

    Linares Gonzalez, J.; Barahona Fernandez, E.; Huertas Garcia, F.; Caballero Mesa, E.; Cuadros Ojeda, J.

    1996-01-01

    The use of bentonite as backfilling and sealing material in the high level radioactive waste disposals has been treated in previous studies accomplished by different authors. However, the use of this clayey barrier needs the resolution of different problems so that its efficiency will be enhanced. between those could be cited the study of the actual capacity of sealing the space around the canister and the accommodation to the pressure of the rocky environment; the possible variations in plasticity; the diffusion and reaction processes that can be produced through the barrier by groundwater, the capacity of radionuclides adsorption, etc. These studies, show that the bentonites with high content in smectite fulfill satisfactorily with the physical and chemical conditions to be used as sealing material, but it is known that the smectite can be unstable in diagenetic conditions similar to those are given in a deep repository of radioactive wastes, being transformed into illite. A conclusion of immediate interest is deduced from this last study. The bentonites used as sealing material in radioactive waste repositories must no contain Na as interlayer cation since it is very easily exchangeable by K. It is better to select those smectites with Ca and Mg that detain the entry of K in the interlayer and as a consequence the transformation process of smectite into illite is made more difficult. (Author)

  15. Optimization of bentonite pellet properties

    International Nuclear Information System (INIS)

    Sanden, Torbjoern; Andersson, Linus; Jonsson, Esther; Fritzell, Anni

    2012-01-01

    Document available in extended abstract form only. SKB in Sweden is developing and implementing concepts for the final disposal of spent nuclear fuel. A KBS-3V repository consists of a deposition tunnel with copper canisters containing spent fuel placed in vertical deposition holes. The canisters are embedded in highly compacted bentonite. After emplacement of canisters and bentonite blocks, the tunnels will be backfilled and sealed with an in-situ cast plug at the entrance. The main concept for backfilling the deposition tunnels imply pre compacted blocks of bentonite stacked on a bed of bentonite pellet. The remaining slot between blocks and rock will be filled with bentonite pellets. The work described in this abstract is a part of the ASKAR-project which main goal is to make a system design based on the selected concept for backfilling. Immediately after starting the backfill installation, inflowing water from the rock will come in contact with the pellet filling and thereby influence the characteristics of the pellet filling. The pellet filling helps to increase the average density of the backfill, but one of the most important properties beside this is the water storing capacity which will prevent water from reaching the backfill front where it would disturb and influence the quality of the installation. If water flows through the pellet filling out to the backfilling front, there will be erosion of material which also will affect the quality of the installed backfill. In order to optimize the properties regarding water storing capacity and sensitivity for erosion a number of tests have been made with different pellet types. The tests were made in different scales and with equipment specially designed for the purpose. The performed tests can be divided in four parts: 1. Standard tests (determining water content and density of pellet fillings and individual pellets, compressibility of the pellet fillings and strength of the individual pellets); 2. Erosion

  16. Stagnation, circulation, and erosion of granular materials through belt conveyor sluice gate

    Science.gov (United States)

    Pohlman, Nicholas; Moralda, Michael; Dunne, Ryan

    2013-11-01

    Control of flow rates in conversion reactors for discrete materials like biomass can be achieved in belt conveyors through a combination of belt speed, hopper size, and aperture opening. As material is extracted from the bottom of the storage hopper, other material cannot achieve plug flow and therefore is restricted from exiting through a sluice-gate type opening. The excess material moves vertically from the opening causing a pile up and recirculation back along the free surface of the hopper. Experimental results obtained through high speed imaging show the position of the stagnation point as well as the rate of circulation is dependent on the mass flow rate achieved and instantaneous fill level. The movement of material into the plug flow along the belt allows verification of deposition models on erodible beds rather than rigid surfaces with artificial roughness of glued particles. Similarly, the pile-up at the exit influences the efficiency of the transport affecting the narrow energy return on investment of biomass resources. The laboratory-scale behavior can therefore be translated into industrial performance metrics for increased operational efficiency. This work is supported by the NSF REU Site Operation E-Tank under award number 1156789.

  17. Localization and Instability in Sheared Granular Materials: Role of Pore Fluids and Non-monotonic Rate Dependent Rheology

    Science.gov (United States)

    Ma, X.; Elbanna, A. E.; Kothari, K.

    2017-12-01

    Fault zone dynamics hold the key to resolving many outstanding geophysical problems including the heat flow paradox, discrepancy between fault static and dynamic strength, and energy partitioning. Most fault zones that generate tectonic events are gouge filled and fluid saturated posing the need for formulating gouge-specific constitutive models that capture spatially heterogeneous compaction and dilation, non-monotonic rate dependence, and transition between localized and distributed deformation. In this presentation, we focus primarily on elucidating microscopic underpinnings for shear banding and stick-slip instabilities in sheared saturated granular materials and explore their implications for earthquake dynamics. We use a non-equilibrium thermodynamics model, the Shear Transformation Zone theory, to investigate the dynamics of strain localization and its connection to stability of sliding in the presence and absence of pore fluids. We also consider the possible influence of self-induced mechanical vibrations as well as the role of external acoustic vibrations as analogue for triggering by a distant event. For the dry case, our results suggest that at low and intermediate strain rates, persistent shear bands develop only in the absence of vibrations. Vibrations tend to fluidize the granular network and de-localize slip at these rates. Stick-slip is only observed for rough grains and it is confined to the shear band. At high strain rates, stick-slip disappears and the different systems exhibit similar stress-slip response. Changing the vibration intensity, duration or time of application alters the system response and may cause long-lasting rheological changes. The presence of pore fluids modifies the stick slip pattern and may lead to both loss and development of slip instability depending on the value of the confining pressure, imposed strain rate and hydraulic parameters. We analyze these observations in terms of possible transitions between rate

  18. Micro-mechanical investigation of the effect of fine content on mechanical behavior of gap graded granular materials using DEM

    Directory of Open Access Journals (Sweden)

    Taha Habib

    2017-01-01

    Full Text Available In this paper, we present a micro-mechanical study of the effect of fine content on the behavior of gap graded granular samples by using numerical simulations performed with the Discrete Element Method. Different samples with fine content varied from 0% to 30% are simulated. The role of fine content in reinforcing the granular skeleton and in supporting the external deviatoric stress is then brought into the light.

  19. Analysis and Modeling of Process of Residual Deformations Accumulation in Soils and Granular Materials

    Science.gov (United States)

    Aleksandrov, A. S.; Dolgih, G. V.; Kalinin, A. L.

    2017-11-01

    It is established that under the influence of repeated loads the process of plastic deformation in soils and discrete materials is hereditary. To perform the mathematical modeling of plastic deformation, the authors applied the integral equation by solution of which they manage to obtain the power and logarithmic dependencies connecting plastic deformation with the number of repeated loads, the parameters of the material and components of the stress tensor in the principal axes. It is shown that these dependences generalize a number of models proposed earlier in Russia and abroad. Based on the analysis of the experimental data obtained during material testing in the dynamic devices of triaxial compression at different values of the stress deviator, the coefficients in the proposed models of deformation are determined. The authors determined the application domain for logarithmic and degree dependences.

  20. Customized bentonite pellets. Manufacturing, performance and gap filling properties

    Energy Technology Data Exchange (ETDEWEB)

    Marjavaara, P.; Holt, E.; Sjoeblom, V. [VTT Technical Research Centre of Finland, Espoo (Finland)

    2013-12-15

    The goal of this work was to provide knowledge about how to manufacture customized bentonite pellets and how customized bentonite pellets perform in practice during the nuclear repository construction process. The project was mainly focused on laboratory experimental tests to optimize the pellet filling by customizing the raw materials and pellet manufacturing. Bentonite pellets were made using both extrusion and roller compaction methods. The pellets were intended for use in gaps between compacted bentonite and the rock walls in both buffer deposition holes and tunnel backfilling. Performance of different types of custom-made pellets were evaluated with regard to their ease of manufacturing, density, crush strength, abrasion resistance, water holding capacity, free swelling and also their thermal conductivity. These evaluations were done in both Finland (by VTT) and Canada (by AECL). Over 50 different varieties of pellets were roller-compaction manufactured at AECL in Canada and 20 types of extrusion pellets at VTT in Finland. The parameters that were varied during manufacturing included: bentonite raw material type, water content, pellet sizes, bentonite compaction machine parameters, use of recycled pellets, and addition of two different types of filler (illite or granitic sand) at varying addition percentages. By examining the pellets produced with these methods and materials the performance and behaviour of the bentonite pellets were evaluated in laboratory with selected tests. The work done using extrusion pellets showed that it was possible to manufacture pellets with higher water contents, up to 21 % from MX-80. This water content value was higher than what was typically possible using roller-compaction method in this study. Higher water content values allow closer compatibility with the designed bentonite buffer water content. The extrusion tests also showed that the required production simulation runs could be made successfully with reference type of MX

  1. Influence of Fines Content on Consolidation and Compressibility Characteristics of Granular Materials

    Science.gov (United States)

    Lipiński, Mirosław J.; Wdowska, Małgorzata K.; Jaroń, Łukasz

    2017-10-01

    Various behaviour of soil under loading results to large extent from kind of soil considered. There is a lot of literature concerning pure sand or plastic clays, while little is known about materials, which are from classification point of view, between those soils. These materials can be considered as cohesionless soils with various fines content. The paper present results of tests carried out in large consolidometer on three kinds of soil, containing 10, 36 and 97% of fines content. Consolidation, permeability and compressibility characteristics were determined. Analysis of the test results allowed to formulate conclusion concerning change in soil behaviour resulting from fines content.

  2. Investigation on the effect of seawater to hydraulic property and wetting process of bentonite

    International Nuclear Information System (INIS)

    Hasegawa, Takuma

    2004-01-01

    On high-level waste disposal, bentonite is one of the most promising material for buffer and backfill material. The hydraulic properties and wetting process of bentonite are important not only for barrier performance assessment but also for prediction of waste disposal environment, such as resaturation time and thermal distribution. In Japan, we should consider the effect of seawater for bentonite, because radioactive waste will be disposed of in coastal area and in marine sediment where seawater remained. However, it is not enough to understand the effect of seawater. Therefore, experimental study was conducted to investigate the effect of seawater on the hydraulic conductivity and wetting process of bentonite. The effect of seawater on hydraulic conductivity is significant for Na-bentonite, the hydraulic conductivity of Na-bentonite in seawater is one order to magnitude higher than that in distilled water. On the other hand, the hydraulic conductivity of Ca-bentonite is not influenced by seawater. The hydraulic conductivity of bentonite decreases as effective montmorillonite density increases. The effective montmorillonite density is ratio between the weight of montmorillonite and volume of porosity and montmorillonite. The hydraulic conductivity of bentonite is close related to swelling property since the hydraulic conductivity decrease as the swelling pressure increase. Wetting process of compacted bentonite could be evaluated by diffusion phenomena since infiltration rate and change of saturation rate and represented by diffusion equation. The effect of seawater on water diffusivity is significant for Na-type bentonite with low effective montmorillonite density. Except for that condition, the water diffusivity of bentonite is almost constant and is not influenced by effective montmorillonite density and seawater. (author)

  3. Normal Stresses in a Granular Material Under Falling Weight Deflectometer loading

    DEFF Research Database (Denmark)

    Ullidtz, Per; Askegaar, Vagn; Sjølin, Finn Ole

    1996-01-01

    The vertical normal stress under a falling weight deflectometer (FWD) was measured in a sand. The material had more than 90 percent falling within the sand fraction from 60 micrometer to 2 mm. The stress was measured with three different transducers. All transducers were installed at a depth of 2...

  4. Comparison of the release of constituents from granular materials under batch and column testing.

    Science.gov (United States)

    Lopez Meza, Sarynna; Garrabrants, Andrew C; van der Sloot, Hans; Kosson, David S

    2008-01-01

    Column leaching testing can be considered a better basis for assessing field impact data than any other available batch test method and thus provides a fundamental basis from which to estimate constituent release under a variety of field conditions. However, column testing is time-intensive compared to the more simplified batch testing, and may not always be a viable option when making decisions for material reuse. Batch tests are used most frequently as a simple tool for compliance or quality control reasons. Therefore, it is important to compare the release that occurs under batch and column testing, and establish conservative interpretation protocols for extrapolation from batch data when column data are not available. Five different materials (concrete, construction debris, aluminum recycling residue, coal fly ash and bottom ash) were evaluated via batch and column testing, including different column flow regimes (continuously saturated and intermittent unsaturated flow). Constituent release data from batch and column tests were compared. Results showed no significant difference between the column flow regimes when constituent release data from batch and column tests were compared. In most cases batch and column testing agreed when presented in the form of cumulative release. For arsenic in carbonated materials, however, batch testing underestimates the column constituent release for most LS ratios and also on a cumulative basis. For cases when As is a constituent of concern, column testing may be required.

  5. MICROCT AND PREPARATION OF ß-TCP GRANULAR MATERIAL BY THE POLYURETHANE FOAM METHOD

    Directory of Open Access Journals (Sweden)

    Robert Filmon

    2011-05-01

    Full Text Available Commercial ß-tricalcium phosphate (ß-TCP is commercialy available in granules manufactured by sintering of powders. We have evaluated the different steps of the manufacturing process of ß-TCP ceramics granules prepared from blocks obtained with the polyurethane foam technology. Three types of slurry were prepared with 10, 15 and 25 g of ß-TCP per gram of polyurethane foam. Analysis was done by scanning electron microscopy, EDX, Raman spectroscopy and microcomputed tomography combined with image analysis. A special algorithm was used to identify the internal microporosity (created by the calcination of the foam from the internal macroporosity due to the spatial repartition of the material. The low ß-TCP dosages readily infiltrated the foam and the slurry was deposited along the polymer rods. On the contrary, the highest concentration produced inhomogeneous infiltrated blocks and foam cavities appeared completely filled in some areas. 2D microcomputed sections and reconstructed 3D models evidenced this phenomenon and the frequency distribution of the thickness and separation of material trabeculae confirmed the heterogeneity of the distribution. When crushed, blocks prepared with the 25 g slurry provided the largest and irregular granulates.

  6. Long-term stability of bentonite. A literature review

    International Nuclear Information System (INIS)

    Laine, H.; Karttunen, P.

    2010-07-01

    The long-term thermodynamic stability of the bentonite buffer in the evolving chemical, thermal and hydrological conditions at Olkiluoto has been evaluated by reviewing the relevant experimental data and natural occurrences of bentonite that could serve as analogues for the long-term bentonite stability in the expected repository conditions, especially focussing on mineral transformations due, among others, to thermal effects including cementation. Natural occurrences with stable smectite have been reviewed and compared with Olkiluoto groundwater compositions at present and during the expected hydrogeochemical evolution of the repository. Alteration of the bentonite buffer is expected to be insignificant for natural groundwater conditions at present and for the evolving groundwater conditions at the expected thermal boundary conditions caused by the heat induced from the fuel canisters ( + and SiO 2 and elevated pH due to degradation and dissolution processes. These may alter the conditions in the repository that may favour alteration and cementation processes. The amounts of foreign materials to be used in the repository will be updated along with the progress of the construction. Also the information on their impact on the barriers needs to be evaluated in more detail, including the degradation rate, mobility or dilution of the foreign materials in the repository environment. The exchangeable cation composition of the buffer bentonite is expected to equilibrate with the surrounding groundwater during and after saturation. This process is expected to lead towards Ca-dominant exchangeable cation composition within the montmorillonite interlayer spaces in the buffer. In general it seems that the transformation towards Ca-dominated composition would favour the long-term stability of the buffer as Ca-dominated smectite (compared to Na-dominated type) has larger water retention capacity and anion incorporation to the interlayer space of montmorillonite is more

  7. Polyaniline (PANI) modified bentonite by plasma technique for U(VI) removal from aqueous solution

    Science.gov (United States)

    Liu, Xinghao; Cheng, Cheng; Xiao, Chengjian; Shao, Dadong; Xu, Zimu; Wang, Jiaquan; Hu, Shuheng; Li, Xiaolong; Wang, Weijuan

    2017-07-01

    Polyaniline (PANI) modified bentonite (PANI/bentonie) was synthesized by plasma induced polymerization of aniline on bentonite surface, and applied to uptake of uranium(VI) ions from aqueous solution. The as-synthesized PANI/bentonie was characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), thermal gravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). Batch adsorption technique was utilized to investigate the adsorption of U(VI) on bentonite and PANI/bentonite. The adsorption of U(VI) (10 mg/L) on PANI/bentonite surface is fairly depend on solution pH, ionic strength, and temperature in solution. The modified PANI on PANI/bentonite surface significantly enhances its adsorption capability for U(VI). The presence of humic acid (HA) can sound enhance U(VI) adsorption on PANI/bentonite at pH 6.5. According to the thermodynamic parameters, the adsorption of U(VI) on PANI/bentonite surface is a spontaneous and endothermic process. The results highlight the application of PANI/bentonite composites as candidate material for the uptake of trace U(VI) from aqueous solution.

  8. Characterization of organo-modified bentonite sorbents: The effect of modification conditions on adsorption performance

    Science.gov (United States)

    Parolo, María E.; Pettinari, Gisela R.; Musso, Telma B.; Sánchez-Izquierdo, María P.; Fernández, Laura G.

    2014-11-01

    The organic modification of a natural bentonite was evaluated using two methods: exchanging the interlayer cations by hexadecyltrimethylammonium (HDTMA) and grafting with vinyltrimethoxysilane (VTMS) and γ-methacryloyloxy propyl trimethoxysilane (TMSPMA) on montmorillonite surface. The physicochemical characterization of all materials was made by X-ray diffraction (XRD), IR spectroscopy, thermogravimetric analysis (TGA) and Brunauer-Emmett-Teller (BET) surface area techniques. HDTMA cations and organosilanes were intercalated into the interlayer space of montmorillonite, as deduced from the increase of the basal spacing. IR spectroscopy, TGA and BET area give evidence of successful organic modification. The studies show a decrease in the IR absorption band intensity at 3465 cm-1 with surfactant modification, and also a decrease of mass loss due to adsorbed water observed in two samples: the organoclay and functionalized bentonites, which are evidences of a lower interlayer hydrophilicity. The efficiency of aniline removal onto natural bentonite, organobentonite and functionalized bentonites from aqueous solutions was evaluated. Aniline sorption on natural bentonite was studied using batch experiments, XRD and IR spectroscopy. The hydrophobic surface of organobentonite and functionalized bentonites increased the retention capacity for nonionic organic substances such as aniline on bentonites. The sorption properties of modified bentonite, through different modification methods, enhanced the potential industrial applications of bentonites in water decontamination.

  9. A study of the condition for the passivation of carbon steel in bentonite

    International Nuclear Information System (INIS)

    Taniguchi, Naoki; Morimoto, Masataka; Honda, Akira

    1999-01-01

    It is important to study the corrosion behavior of materials to be used for overpack for high-level radioactive waste disposal. Carbon steel is one of the candidate materials. The type of corrosion on carbon steel depends on whether the carbon steel is passivated or not. In this study, the condition for the passivation of carbon steel was studied using bentonite as the buffer material. Anodic polarization in bentonite and the measurements of pH of porewater in bentonite was measured. The results of these experiments showed that the possibility of passivation is small in highly compacted bentonite in groundwater in Japan. Therefore, localized corrosion on carbon steel due to the breakdown of passive film is unlikely in bentonite. In other words, general corrosion seems to be the most probable type of corrosion under repository condition in Japan. (author)

  10. Electromagnetic properties of Fe-Co granular composite materials containing acicular nanoparticles

    Science.gov (United States)

    Kasagi, Teruhiro; Massango, Herieta; Tsutaoka, Takanori; Yamamoto, Shinichiro; Hatakeyama, Kenichi

    2018-03-01

    Electromagnetic properties of acicular (needle-like) Fe76Co24 nanoparticle composite materials have been studied in microwave frequency range up to 20 GHz. The Fe76Co24 particles are commercially available acicular Fe76Co24 nanoparticles with an approximate length and diameter of 100 and 25 nm, respectively. The Fe76Co24 nanocomposites were prepared by embedding the Fe76Co24 nanoparticle in an appropriate resin. Since the metallic Fe76Co24 nanoparticles have an oxidized surface, even high particle content composites at 78 vol.%, which is in the percolated state, does not show metallic conduction; a low frequency plasmonic state with the negative permittivity spectrum was not observed. Meanwhile, the negative permeability spectrum caused by the magnetic resonance in Fe76Co24 alloy was obtained in the high particle content composites. From the measurement of the complex permeability spectra under the external dc magnetic field, it was clarified that the gyromagnetic spin rotation mainly contributes to the permeability spectrum of nanocomposites due to extremely small quantity of domain walls in the acicular nanoparticles. This result suggests that the negative permeability spectrum was caused by the gyromagnetic spin resonance. By the comparison of the complex permeability spectrum between the acicular Fe76Co24 nanocomposite and the spherical Fe50Co50 microcomposite, the gyromagnetic spin resonance frequency of the acicular nanocomposite tends to locate higher than that of the spherical microcomposite owing to the demagnetizing field effect. Therefore, it can be concluded that the negative permeability frequency band of the acicular nanocomposite is higher than that of the spherical microcomposite at the same particle content.

  11. Investigation of alteration behaviour of compacted bentonite contracted with carbon steel for 10 years

    International Nuclear Information System (INIS)

    Suyama, Tadahiro; Ueno, Kenichi; Sasamoto, Hiroshi

    2008-03-01

    behavior of bentonite by interactions with iron material in our previous studies. According to the results of batch type experiments, some changes like ion type change from Na to Fe type smectite and production of very small amount of non-swelling minerals etc. were identified after experiments. However, no change was identified for the present study using compacted bentonite, although the iron migration in compacted bentonite was observed. In conclusion, in order to evaluate the iron-bentonite interactions in compacted system like repository conditions, it would be important not to utilize directly the results by batch type experiments but understand the phenomena which would be occurred in compacted bentonite. (author)

  12. Microstructural modifications induced by hydraulic and mechanical actions on compacted bentonite

    International Nuclear Information System (INIS)

    Romero, E.; Suriol, J.; Lloret, A.; Castellanos, E.; Villar, M.V.

    2010-01-01

    Document available in extended abstract form only. The hydration of bentonite generates microstructural changes that modify both its hydraulic and mechanical properties. As a consequence, the evolution of porosity and microstructure influence greatly the hydration transient state. Measurements and observations at this microstructural level are very important, since they help in further understanding higher structural levels and their consequences on material properties and behaviour under various hydro-mechanical stress state conditions. To accomplish the complex issue of microstructural studies, several techniques have to be applied. A very useful technique for the quantitative study at the microscale is mercury intrusion porosimetry (MIP), since the range of pore diameters that can be examined (from 6 nm to 400 μm) is very wide. The influence of various mechanical (loading) and hydraulic (wetting / drying) stress paths on the pore size distribution of compacted bentonite was analysed. Some of the conclusions reached are: - The pore size distribution is clearly bi-modal. The dominant values are 10 nm, which would correspond to the pores inside clay aggregates that are not affected by the magnitude of the compaction load, and a larger pore size, which depends on compaction degree and ranges from 20 μm (for ρd=1.68 g/cm 3 ) to 30 μm (for ρd = 1.4 g/cm 3 ). These larger voids would correspond to the inter-granular pores. The boundary between the two pore size families is around 150-200 nm. The same pattern is found irrespective of the clay water content. - There exists a significant pore volume into which the mercury cannot penetrate because it corresponds to pores smaller than 6 nm, and it is the same irrespective of the density of the specimens. - The inter-granular pores disappear when a clay slurry is compacted. - After wetting of compacted samples, the hindered and latent inter-aggregate pore size mode emerges (350 and 1100 nm). Simultaneously, and as a

  13. An analysis of the factors affecting the hydraulic conductivity and swelling pressure of Kyungju ca-bentonite for use as a clay-based sealing material for a high level waste repository

    International Nuclear Information System (INIS)

    Cho, Won Jin; Lee, Jae Owen; Kwon, Sang Ki

    2012-01-01

    The buffer and backfill are important components of the engineered barrier system in a high-level waste repository, which should be constructed in a hard rock formation at a depth of several hundred meters below the ground surface. The primary function of the buffer and backfill is to seal the underground excavation as a preferred flow path for radionuclide migration from the deposited high-level waste. This study investigates the hydraulic conductivity and swelling pressure of Kyungju Ca-bentonite, which is the candidate material for the buffer and backfill in the Korean reference high-level waste disposal system. The factors that influence the hydraulic conductivity and swelling pressure of the buffer and backfill are analyzed. The factors considered are the dry density, the temperature, the sand content, the salinity and the organic carbon content. The possibility of deterioration in the sealing performance of the buffer and backfill is also assessed.

  14. Behavior of pressure and viscosity at high densities for two-dimensional hard and soft granular materials

    NARCIS (Netherlands)

    Otsuki, Michio; Hayakawa, Hisao; Luding, Stefan

    2010-01-01

    The pressure and the viscosity in two-dimensional sheared granular assemblies are investigated numerically. The behavior of both pressure and viscosity is smoothly changing qualitatively when starting from a mono-disperse hard-disk system without dissipation and moving towards a system of (i)

  15. Study on the saturating and swelling behavior of an engineering bentonite barrier using a test model

    International Nuclear Information System (INIS)

    Nakajima, Makoto; Kobayashi, Ichizo; Toida, Masaru; Fujisaki, Katsutoshi

    2007-01-01

    The conceptual design of a disposal facility with additional buffer depth for radioactive waste is mainly constituted from the multi-barrier system that is constructed around the waste form so that it prevents radionuclide transfer to the biosphere. The engineered bentonite barrier is one of the elements of the multi-barrier system and is constructed with homogeneous bentonite-containing material compacted to a high density so that there are no voids. Due to the swelling characteristics of the bentonite material, the self-sealing function which is an important function of the bentonite barrier can work, but at the same time it mechanically affects the neighboring structures. Therefore, an experimental study was implemented in order to evaluate the mechanical effect of the bentonite swelling behavior throughout the construction, emplacement operations and closure re-saturation phase. In this article, the results of swelling tests to obtain the mechanical properties of the bentonite and three types of test model experiments performed for the event observations in the different saturation processes are described. As a result, the effects of a seepage pattern of ground water and a variation in the density produced by construction on the swelling pressure distribution of the bentonite barrier could be reproduced and validated. It is thought that they will be important events when ground water permeates the bentonite layer of a multiple barrier system. (author)

  16. Hydrothermal alkaline stability of bentonite barrier by concrete interstitial wastes

    International Nuclear Information System (INIS)

    Leguey Jimenez, S.; Cuevas Rodriguez, J.; Ramirez Martin, S.; Vigil de la villa Mencia, R.; Martin Barca, M.

    2002-01-01

    At present, the main source of High Level radioactive Waste (HLW) is the electrical energy production during all the steps of developing. In almost all the countries with nuclear programs, the option for the final management of HLW is the Deep Geological Repository (DGR) based on the concept of multi barrier. According to this concept, the waste is isolated from biosphere by the interposition of confinement barriers. Two of the engineering barriers in the Spanish design of DGR in granitic rock are compacted bentonite and concrete. The bentonite barrier is the backfilling and sealing material for the repository gallery, because of its mechanical and physico-chemical properties. The main qualities of concrete as a component of a multi barrier system are its low permeability, mechanical resistance and chemical properties. With regard to chemical composition of concrete, the alkaline nature of cement pore water lowers the solubility of many radioactive elements. However, structural transformation in smectite, dissolution or precipitation of minerals and, consequently, changes in the bentonite properties could occurs in the alkaline conditions generated by the cement degradation. The main objective of the present work is to evaluate the effect of concrete in the stability of Spanish reference bentonite (La Serrata of Nijar, Almeria, Spain) in conditions similar to those estimated in a DGR in granitic rock. Because of the main role of bentonite barrier in the global performance of the repository, the present study is essential to guarantee its security. (Author)

  17. Observations of bentonite-hyper-alkaline fluid and bentonite-cement interactions by the X-ray computed tomography

    International Nuclear Information System (INIS)

    Nakabayashi, R.; Chino, D.; Kawaragi, C.; Sato, T.; Yoneda, T.; Kaneko, K.; Shibata, S.; Sakamoto, H.

    2010-01-01

    even though it is a powerful tool to obtain information on chemical distribution with high special resolution. X-ray CT, on the contrary, is a powerful and non-destructive analytical tool to study the micro- and inner-structure of materials and can provide an opportunity to conduct measurement on the same sample at different position and time. Therefore, X-ray CT has a high potential to obtain many images with digital data to trace the alteration process in bentonite-hyper-alkaline fluid and bentonite-cement interactions as a function of time. In this context, the advective alteration experiments for the bentonite column with lower density and diffusive alteration experiments for the compacted bentonite sandwiched by cement pellets were conducted to observe the micro-structural changes in the sampled by X-ray CT. For the advective alteration experiments, Na-bentonite specimens (Kunigel V1) with densities of 0.3 Mg/m 3 and 0.4 Mg/m 3 were used. NaOH solution (pH 13.5) with 0.3 M passed through the bentonite specimens with flow pressure of 0.03 and 0.04 MPa, respectively. The specimens were kept inside the oven at 80 deg. C. The flow-through periods of NaOH solution for bentonite specimens were conducted for 200 days. On the other hand, for diffusive alteration experiments, the compacted Na-type bentonite (Kunigel V1) sandwiched by ordinary portland cement (W/C 0.6) initially immersed in ion-exchange water for 100 days at 50 deg. C. Both of the specimens were observed by X-ray CT every 10 days. For advective alteration experiments, the effluent was periodically collected, and the coefficient of permeability and solution pH were measured. The reacted solid was analyzed by X-ray powder diffraction (XRD) after the experiments were terminated. The concentration of Al in the effluent was determined by using inductively coupled plasma-atomic emission spectroscopy (ICP-AES), while Si concentration was determined as SiO 2 through molybdenum-blue spectrometry. In the case of

  18. Dismantling of the EB experiment: Experimental research on the retrieved GBM and bentonite blocks

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jiang-Feng, E-mail: jeafliu@hotmail.com [State Key Laboratory for Geomchanics & Deep Underground Engineering, and School of Mechanics and Civil Engineering, China University of Mining & Technology, Xuzhou, Jiangsu 221116 (China); Laboratoire de Méchanique de Lille (LML), and École Centrale de Lille, BP 48, F-59651 Villeneuve d’Ascq Cedex (France); Skoczylas, Frédéric [Laboratoire de Méchanique de Lille (LML), and École Centrale de Lille, BP 48, F-59651 Villeneuve d’Ascq Cedex (France); Talandier, Jean [ANDRA, 1-7 rue Jean Monnet, 92298 Châtenay-Malabry Cedex (France); Pu, Hai [State Key Laboratory for Geomchanics & Deep Underground Engineering, and School of Mechanics and Civil Engineering, China University of Mining & Technology, Xuzhou, Jiangsu 221116 (China)

    2016-04-15

    Graphical abstract: - Highlights: • We present a demonstration of a new concept of HLW (high-level waste) repositories. • The hydro-mechanical characteristics of GBM and blocks were determined. • The water retention curves (WRCs) of GBM and blocks were presented. • The effective gas permeability of the GBM and blocks were measured. • The homogeneity of the GBM and blocks were investigated. - Abstract: The Engineered Barrier Emplacement Experiment in Opalinus Clay (EB experiment) was a full-scale test for the demonstration of a new concept of high-level waste (HLW) repositories in horizontal drifts in the Opalinus Clay formation. After 10.5 years of hydration, the EB experiment was dismantled in autumn 2012. Samples obtained from the granular bentonite material (GBM), and bentonite blocks were sent to a laboratory for further analysis. The bentonite samples analyzed at the Laboratory of Mechanic of Lille (LML) were obtained from the CMT1, CMT2, CMT3 and RW sections. Their physical states were determined, as were their effective gas permeability and swelling capacity at different relative humidity (RH) levels. The results indicate that the water contents of the GBM determined in the laboratory ranged between 25.63% and 44.88% and that the dry densities ranged between 1.13 and 1.44 g/cm{sup 3}. The blocks had water contents similar to (or slightly higher than) those of the GBM, and their dry densities had decreased from an initial value of 1.69 g/cm{sup 3} to values close to 1.30 g/cm{sup 3}, which were similar to the average values found in the GBM. The effective gas permeabilities of the GBM samples were within the range of 1.50 × 10{sup −22} m{sup 2} and 1.03 × 10{sup −17} m{sup 2}, whereas, the corresponding values of the samples obtained from the blocks were between 2.20 × 10{sup −21} m{sup 2} and 5.12 × 10{sup −21} m{sup 2}. The permeability values are primarily related to the dry densities and water contents of the samples. Contact with

  19. Preliminary Study on Benzoic Acid Adsorption from Crude Active Coals and Bentonite

    Directory of Open Access Journals (Sweden)

    Abbes Boucheta

    2016-04-01

    Full Text Available We studied the adsorption of pollutant benzoic acid by the modified bentonite of Maghnia (west of Algeria, and coal (Coal from the mines, southwest of Algeria, Bechar area under three forms, crude and activated. Kinetic data show that the balance of bentonite (as amended adsorbs organic acids better than activated and raw coal. Indeed, the intercalation of bentonite with benzoic acid causes an improvement in the texture of porous material, which allows its use in the adsorption of organic compounds. The adsorption isotherms (Langmuir and Freundlich indicate that the adsorption of benzoic acid by the coal and bentonite yielded results favorably. The results obtained showed the practical value of using the activated coal and bentonite (as amended in the field of remediation of water contaminated with organic pollutants

  20. Cytotoxicity and mechanical behavior of chitin-bentonite clay based polyurethane bio-nanocomposites.

    Science.gov (United States)

    Zia, Khalid Mahmood; Zuber, Mohammad; Barikani, Mehdi; Hussain, Rizwan; Jamil, Tahir; Anjum, Sohail

    2011-12-01

    Chitin based polyurethane bio-nanocomposites (PUBNC) were prepared using chitin, Delite HPS bentonite nanoclay enriched in montmorillonite (MMT), 4,4'-diphenylmethane diisocyanate (MDI) and polycaprolactone polyol CAPA 231 (3000 g/mol(-1)). The prepolymers having different concentration of Delite HPS bentonite nanoclay were extended with 2 moles of chitin. The structures of the resulted polymers were determined by FT-IR technique. The effect of nanoclay contents on mechanical properties and in vitro biocompatibility was investigated. The mechanical properties of the synthesized materials were improved with increase in the Delite HPS bentonite nanoclay contents. Optimum mechanical properties were obtained from the PU bio-nanocomposite samples having 4% Delite HPS bentonite nanoclay. The results revealed that the final PU bio-nanocomposite having 2% Delite HPS bentonite nanoclay contents is ideal contenders for surgical threads with on going investigations into their in vitro biocompatibility, non-toxicity, and mechanical properties. Copyright © 2011 Elsevier B.V. All rights reserved.

  1. Characterization of Cr/Bentonite and HZSM-5 Zeolite as Catalysts for Ethanol Conversion to Biogasoline

    Directory of Open Access Journals (Sweden)

    Robert Ronal Widjaya

    2012-04-01

    Full Text Available In this research it has been done characterization on Cr/Bentonit and Zeolit HZSM-5 catalysts for ethanol catalytic process to biogasoline (equal to gasoline. Cr/Bentonit has high acidity and resistant to a lot of moisture, so in addition to being able to processing feed which a lot of moisture (>15% from ethanol-water mixture, also it is not easy deactivated. Cr/Bentonit which is then used as the catalyst material on the process of ethanol conversion to be biogasoline and the result was compared with catalyst HZSM-5 zeolite. Several characterization methods: X-ray diffraction, Brunauer Emmett Teller (BET, thermogravimetry analysis (TGA, and catalyst activity tests using catalytic Muffler instrument and gas chromatography-mass spectrometry (GC-MS for product analysis were performed on both catalysts. From acidity measurement, it is known that acidity level of Cr/Bentonit is the highest and also from XRD result, it is known there is shift for 2theta in Cr/Bentonit, which indicates that Cr-pillar in the Bentonite can have interaction. It is also supported by BET data that shows the addition of specific surface are in Cr/Bentonite compared with natural Bentonite before pillarization. Futhermore catalyst activity test produced the results, analyzed by GC-MS, identified as butanol and also possibly formed hexanol, decane, dodecane, undecane, which are all included in gasoline range (C4 until C12.

  2. Theory and calculation of water distribution in bentonite in a thermal field

    International Nuclear Information System (INIS)

    Carnahan, C.L.

    1988-09-01

    Highly compacted bentonite is under consideration for use as a buffer material in geological repositories for high-level radioactive wastes. To assess the suitability of bentonite for this use, it is necessary to be able to predict the rate and spatial extent of water uptake and water distribution in highly compacted bentonite in the presence of thermal gradients. The ''Buffer Mass Test'' (BMT) was conducted by workers in Sweden as part of the Stripa Project. The BMT measured uptake and spatial distributions of water infiltrating annuli of compacted MX-80 sodium bentonite heated from within and surrounded by granite rock; the measurements provided a body of data very valuable for comparison to results of theoretical calculations. Results of experiments on adsorption of water by highly compacted MX-80 bentonite have been reported by workers in Switzerland. The experiments included measurements of heats of immersion and adsorption-desorption isotherms. These measurements provide the basis for prediction of water vapor pressures in equilibrium with bentonite having specified adsorbed water contents at various temperatures. The present work offers a phenomenological description of the processes influencing movement of water in compacted bentonite in the presence of a variable thermal field. The theory is applied to the bentonite buffer-water system in an assumed steady state of heat and mass transport, using critical data derived from the experimental work done in Switzerland. Results of the theory are compared to distributions of absorbed water in buffers observed in the Swedish BMT experiments. 9 refs., 2 figs

  3. Migration Behaviour of Strontium in Czech Bentonite Clay

    Directory of Open Access Journals (Sweden)

    Lucie Baborova

    2016-09-01

    Full Text Available The study deals with sorption and diffusion behaviour of strontium in Czech bentonite B75. The study is a part of a research on reactive transport of radioactive contaminants in barrier materials of a deep geological repository of radioactive waste in the Czech Republic. Series of sorption and diffusion experiments with Sr and non-activated Ca bentonite B75 produced in the Czech Republic were performed in two background solutions (CaCl2 and NaCl. On the basis of sorption batch experiments the kinetics of strontium sorption on bentonite was assessed and the sorption isotherms for various experimental conditions were obtained. As a result of performed diffusion experiments the parameters of diffusion (i.e. effective diffusion coefficient De and apparent diffusion coefficient Da were determined. The observed discrepancies between sorption characteristics obtained from the sorption and diffusion experiments are discussed.

  4. Decantation time of evaluation on bentonite clays fractionation

    International Nuclear Information System (INIS)

    Gomes, J.; Menezes, R.R.; Neves, G.A.; Lira, H.L; Santana, L.N.L.

    2009-01-01

    Bentonite clays present a great number of industrial uses, from petroleum to pharmaceutics and cosmetic industry. The bentonite clay present particles with very fine particles that is responsible by the vast application of these materials. However, commercial clays present wide particle size distribution and a significant content of impurities, particularly quartz, in the form of silt and fine silt. So, the aim of this work is to analyze the effect of the stirring and decantation time in the deagglomeration, purification and size separation of the bentonite clay particles from Paraiba. The clays were characterized by X-ray diffraction and particle size distribution. Based on the results it was observed the decantation time give the elimination of the agglomerates formed by submicrometric particles. The uses of decantation column give separation of the fraction below 200nm. (author)

  5. Characterization of bentonite clay from “Greda” deposit

    Directory of Open Access Journals (Sweden)

    Nadežda Stanković

    2011-06-01

    Full Text Available Based on mineralogical and technological investigations of the deposit “Greda” important characteristics of bentonite clay were determined. Representative samples of the deposit were characterized with X-ray diffraction, low-temperature nitrogen adsorption, chemical analysis, differential thermal analysis and scanning electron microscopy. It was determined that the main mineral is montmorillonite and in subordinate quantities kaolinite, quartz and pyrite. The chemical composition generally shows high silica and alumina contents in all samples and small quantities of Fe3+, Ca2+ and Mg2+ cations. Based on technological and mineralogical research, bentonite from this deposit is a high-quality raw material for use in the ceramic industry.

  6. Evaluation of bentonite alteration due to interactions with iron. Sensitivity analyses to identify the important factors for the bentonite alteration

    International Nuclear Information System (INIS)

    Sasamoto, Hiroshi; Wilson, James; Sato, Tsutomu

    2013-01-01

    Performance assessment of geological disposal systems for high-level radioactive waste requires a consideration of long-term systems behaviour. It is possible that the alteration of swelling clay present in bentonite buffers might have an impact on buffer functions. In the present study, iron (as a candidate overpack material)-bentonite (I-B) interactions were evaluated as the main buffer alteration scenario. Existing knowledge on alteration of bentonite during I-B interactions was first reviewed, then the evaluation methodology was developed considering modeling techniques previously used overseas. A conceptual model for smectite alteration during I-B interactions was produced. The following reactions and processes were selected: 1) release of Fe 2+ due to overpack corrosion; 2) diffusion of Fe 2+ in compacted bentonite; 3) sorption of Fe 2+ on smectite edge and ion exchange in interlayers; 4) dissolution of primary phases and formation of alteration products. Sensitivity analyses were performed to identify the most important factors for the alteration of bentonite by I-B interactions. (author)

  7. Some characteristics of potential backfill materials

    International Nuclear Information System (INIS)

    Simpson, D.R.

    1983-05-01

    A backfill material is one of the multiple barriers that may be involved in the disposal of nuclear waste. Such backfill should be a desiccant with the hydrous product having acceptable stability; it should sorb any released radioisotopes, and it should reseal any breached site. The backfill must also have acceptable thermal conductivity. This report presents data on the rate of hydration and the nature of the product of reaction of some candidate backfill materials with water and with brine. Thermal conductivity data is reported for both the reactants and the products. Granular MgO at 150 0 C completely hydrates in less than 10 hours. At 60 0 C and 20 0 C, such extensive hydration requires about 100 and 1000 hours, respectively. The product of the reaction is stable to more than 300 0 C. A doped discalcium silicate was less reactive and the product contains less water of crystallization than the MgO. The reaction product of dicalcium silicate is cementous, but it has low thermal stability. Bentonite readily reacts with water and expands. The reaction product has the properties of vermiculite, which indicates that magnesium ions have diffused into the bentonite structure and are not simply adsorbed on the surface. If bentonite is emplaced in a saline environment, the properties of vermiculite, the reaction product, should also be considered. The thermal conductivity of MgO, discalcium silicate, and bentonite is primarily dependent on the porosity of the sample. A slight increase in thermal conductivity was found with increased temperature, in contrast to most rocks. If the conductive data for the different materials is equated to the same porosity, MgO has the superior thermal conductivity compared to bentonite or discalcium silicate

  8. Natural analogue study for interaction between alkaline groundwater and bentonite at Mangatarem region in the Philippines

    International Nuclear Information System (INIS)

    Tsukada, Y.; Fujita, K.; Nakabayashi, R.; Sato, T.; Yoneda, T.; Yamakawa, M.; Fujii, N.; Namiki, K.; Kasama, T.; Alexander, R.; Arcilla, C.; Pascua, C.

    2012-01-01

    Document available in extended abstract form only. Alteration of bentonite by alkaline leachate from cement/concrete in geological repositories for TRU radioactive waste is deleterious to bentonite performance as a buffer material. Although there have been many laboratory studies on high pH fluid-bentonite interaction for longer term understanding of the behavior of bentonites as buffer materials, different time scales between laboratory experiments and real disposal conditions impede its proper assessment. Thus, a natural analogue study can play an important role in (a) bridging the timescale gaps between laboratory experiments and real disposal conditions and (b) verifying the modeling studies of bentonite stability. Previous natural analogue studies on the cement-bentonite interaction are relatively few. Therefore, this study focuses on the process of serpentinization in ophiolitic rocks which resemble the process of leaching high pH ground waters from cement materials and report the results of study about alkaline water-bentonite interaction in Mangatarem, Philippines. In Mangatarem, in west central Luzon Island in the northern Philippines, there are bentonite quarries in the Aksitero Formation, which is part of the Zambales Ophiolite. Several alkaline hot springs derived from ongoing serpentinization of the ophiolite can be found in close proximity to the bentonite.Through a site characterization (including a foot survey, a series of boreholes and trench excavation in the Saile quarry in Mangatarem, the interface between the bentonite and the pillow lava of the upper ophiolite was confirmed, and chrysotile, a low temperature type of serpentine, was observed in the fault filling by XRD analysis. In the pillow lava, serpentine was also observed inside the fault that cut across both the bentonite and the pillow lava. From these facts, low temperature high pH fluids appears to have passed through the faults and came into contact with the bentonite. In order to

  9. The biological costs of not reclaiming bentonite mine spoils

    Science.gov (United States)

    Carolyn Hull Sieg; Daniel W. Uresk; Richard M. Hansen

    1982-01-01

    Bentonite clay has been mined in the northern Great Plains for more than 80 years. Until the late 1960's, mine spoil materials were left in steep piles and no effort was made to restore biological productivity to these disturbed sites. As a result, unreclaimed spoils are barren and eroded. The biological costs of not reclaiming these spoils are examined in this...

  10. Synthesis of MCM-41 nanomaterial from Algerian bentonite ...

    African Journals Online (AJOL)

    Mesoporous materials of the MCM-41 type were synthesized from Algerian bentonite as an aluminosilicate source without the addition of pure silica and aluminum reagents. The samples were synthesized under hydrothermal condition using cetyltrimithylammonium bromide (CTAB) as surfactant. The influence of initial ...

  11. Performance of Mn2+-modified Bentonite Clay for the Removal

    African Journals Online (AJOL)

    NICOLAAS

    Clay minerals are promising materials for defluoridation of ... edge of the bentonite sheet. ... surface area analyzer (Autosorb-iQ & Quadrasorb SI, USA). .... used to describe chemisorption, as well as cation exchange reac- tions.14 t q. 1. K q. 1.

  12. The Effect of Binder and Waste Granular Materials (WGM on the Shear Strength and Shear Resistance of Dredged Marine Soils (DMS

    Directory of Open Access Journals (Sweden)

    Rosman Mohammad Zawawi

    2017-01-01

    Full Text Available Dredged marine soil (DMS is considered as weak and soft problematic soil. It is possible to give this type of soil a second life if only its geotechnical properties are improved. Infusing soil with solidification agent is the common practice of soil improvement. This study uses binder and waste granular material (WGM such as cement, bottom ash (BA and palm oil clinker (POC. The aforementioned materials are capable to fortify the poor features of the soil. Series numbers of soil bed samples were tested for its shear strength and shear resistance. Test results show that the mentioned soil parameters were corresponded with each other. In short, geo-waste and biomass materials are possible to be reused instead of being discarded.

  13. Granular packing as model glass formers

    International Nuclear Information System (INIS)

    Wang Yujie

    2017-01-01

    Static granular packings are model hard-sphere glass formers. The nature of glass transition has remained a hotly debated issue. We review recent experimental progresses in using granular materials to study glass transitions. We focus on the growth of glass order with five-fold symmetry in granular packings and relate the findings to both geometric frustration and random first-order phase transition theories. (paper)

  14. Distrofia corneal granular

    Directory of Open Access Journals (Sweden)

    Alexeide de la C Castillo Pérez

    Full Text Available Las distrofias corneales constituyen un conjunto de enfermedades que presentan, en su mayoría, una baja incidencia y se caracterizan por acúmulo de material hialino o amiloide que disminuyen la transparencia corneal. La distrofia granular es una enfermedad autosómica dominante que presenta opacidades grises en el estroma superficial central de la córnea y se hacen visibles en la primera y segunda décadas de la vida, lo que provoca disminución de la visión más significativa cerca de los 40 años de edad. Presentamos dos casos clínicos de distrofia granular en pacientes hermanos de diferentes sexos, quienes acudieron a la consulta y refirieron visión nublada. El estudio de la historia familiar nos ayuda en el correcto diagnóstico y la biomicroscopia constituye el elemento más importante.

  15. Modeling of light dynamic cone penetration test - Panda 3 ® in granular material by using 3D Discrete element method

    Science.gov (United States)

    Tran, Quoc Anh; Chevalier, Bastien; Benz, Miguel; Breul, Pierre; Gourvès, Roland

    2017-06-01

    The recent technological developments made on the light dynamic penetration test Panda 3 ® provide a dynamic load-penetration curve σp - sp for each impact. This curve is influenced by the mechanical and physical properties of the investigated granular media. In order to analyze and exploit the load-penetration curve, a numerical model of penetration test using 3D Discrete Element Method is proposed for reproducing tests in dynamic conditions in granular media. All parameters of impact used in this model have at first been calibrated by respecting mechanical and geometrical properties of the hammer and the rod. There is a good agreement between experimental results and the ones obtained from simulations in 2D or 3D. After creating a sample, we will simulate the Panda 3 ®. It is possible to measure directly the dynamic load-penetration curve occurring at the tip for each impact. Using the force and acceleration measured in the top part of the rod, it is possible to separate the incident and reflected waves and then calculate the tip's load-penetration curve. The load-penetration curve obtained is qualitatively similar with that obtained by experimental tests. In addition, the frequency analysis of the measured signals present also a good compliance with that measured in reality when the tip resistance is qualitatively similar.

  16. Radio Frequencies Emitted by Mobile Granular Materials: A Basis for Remote Sensing of Sand and Dust Activity on Mars and Earth

    Science.gov (United States)

    Marshall, J.; Farrell, W.; Houser, G.; Bratton, C.

    1999-01-01

    In recent laboratory experiments, measurements were made of microsecond radio-wave (RF) bursts emitted by grains of sand as they energetically circulated in a closed, electrically ungrounded chamber. The bursts appeared to result from nanoscale electrical discharging from grain surfaces. Both the magnitude and wave form of the RF pulses varied with the type of material undergoing motion. The release of RF from electrical discharging is a well-known phenomenon, but it is generally measured on much larger energy scales (e.g., in association with lightning or electrical motors). This phenomenon might be used to detect, on planetary surfaces, the motion and composition of sand moving over dunes, the turbulent motion of fine particles in dust storms, highly-energetic grain and rock collisions in volcanic eruptions, and frictional grinding of granular materials in dry debris flows, landslides, and avalanches. The occurrence of these discharges has been predicted from theoretical considerations Additional information is contained in the original.

  17. Thermal loading of bentonite. Impact on hydromechanics and permeability

    Energy Technology Data Exchange (ETDEWEB)

    Zihms, Stephanie G.; Harrington, Jon [British Geological Survey, Nickerhill Keyworth (United Kingdom)

    2015-07-01

    Due to its favorable properties, in particular, low permeability and swelling capacity, bentonite has been favored as an engineered barrier and backfill material for the geological storage of radioactive waste. To ensure safe long-term performance it is important to understand any changes in these properties when the material is subject to heat emitting waste. As such, this study will investigate the hydro-mechanical response of bentonite under multi-step thermal loading subject to a constant volume boundary condition. The experimental set up allows continuous measurements of hydraulic and mechanical response during each phase of the thermal cycle. The constant volume cell was placed inside an oven and connected to a hydraulic system with the water reservoir located externally. A pressure gradient of 4 MPa was placed across the sample for the duration of the test in order to map the evolution of permeability. After initial hydration of the bentonite, in this case signified by reaching the asymptote in total stress, the temperature was raised in 20 C increments from 20 to 80 C followed by a final 10 C step to reach 90 C. Each temperature was held constant for at least 7-10 days to allow the stresses and hydraulic transients to equilibrate. This data set will provide an insight into the hydromechanical behavior of the bentonite and the evolution of its permeability when exposed to elevated temperatures.

  18. Pore water chemistry of Rokle Bentonite (Czech Republic)

    International Nuclear Information System (INIS)

    Cervinka, R.; Vejsada, J.

    2010-01-01

    Document available in extended abstract form only. With inflowing the groundwater to Deep Geological Repository (DGR), the interaction of this water with engineering barrier materials will alter both, barrier materials and also the groundwater. One of the most important alterations represents the formation of bentonite pore water that will affect a number of important processes, e.g. corrosion of waste package materials, solubility of radionuclides, diffusion and sorption of radionuclides. The composition of bentonite pore water is influenced primarily by the composition of solid phase (bentonite), liquid phase (inflowing groundwater), the gaseous phase (partial pressure of CO 2 ), bentonite compaction and the rate of groundwater species diffusion through bentonite. Also following processes have to be taken into account: dissolution of admixtures present in the bentonite (particularly well soluble salts, e.g. KCl, NaCl, gypsum), ion exchange process and protonation and deprotonation of surface hydroxyl groups on clay minerals. Long-term stability of mineral phases and possible mineral transformation should not be neglected as well. In the Czech Republic, DGR concept takes local bentonite into account as material for both buffer and backfill. The candidate bentonite comes from the Rokle deposit (NW Bohemia) and represents complex mixture of (Ca,Mg)-Fe-rich montmorillonite, micas, kaolinite and other mineral admixtures (mainly Ca, Mg, Fe carbonates, feldspars and iron oxides). The mineralogical and chemical characteristics were published previously. This bentonite is different in composition and properties from worldwide studied Na-bentonite (e.g. MX-80, Volclay) or Na-Ca bentonite (e.g. Febex). This fact leads to the need of investigation of Rokle bentonite in greater detail to verify its suitability as a buffer and backfill in DGR. Presented task is focused on the study of pore water evolution. Our approach for this study consists in modeling the pore water using

  19. Granular flows in constrained geometries

    Science.gov (United States)

    Murthy, Tejas; Viswanathan, Koushik

    Confined geometries are widespread in granular processing applications. The deformation and flow fields in such a geometry, with non-trivial boundary conditions, determine the resultant mechanical properties of the material (local porosity, density, residual stresses etc.). We present experimental studies of deformation and plastic flow of a prototypical granular medium in different nontrivial geometries- flat-punch compression, Couette-shear flow and a rigid body sliding past a granular half-space. These geometries represent simplified scaled-down versions of common industrial configurations such as compaction and dredging. The corresponding granular flows show a rich variety of flow features, representing the entire gamut of material types, from elastic solids (beam buckling) to fluids (vortex-formation, boundary layers) and even plastically deforming metals (dead material zone, pile-up). The effect of changing particle-level properties (e.g., shape, size, density) on the observed flows is also explicitly demonstrated. Non-smooth contact dynamics particle simulations are shown to reproduce some of the observed flow features quantitatively. These results showcase some central challenges facing continuum-scale constitutive theories for dynamic granular flows.

  20. Evaluation of hydraulic conductivities of bentonite and rock under hyper alkaline and nitrate conditions

    International Nuclear Information System (INIS)

    Iriya, K.; Fujii, K.; Kubo, H.

    2002-02-01

    The chemical conditions of TRU waste repository were estimated as alkaline conditions effected by cementitious materials. And, some TRU wastes include soluble nitrate salt, we have to consider the repository conditions might be high ionic strength condition leaching of nitrate salt. In this study, experimental studies were carried out to evaluate hydraulic conductivities of bentonite and rock under hyper alkaline and nitrate conditions. The followings results were obtained for bentonite. 1) In the immersion experiments of bentonite in hyper alkaline fluids with and without nitrate, the disappearance of montmorillonite of bentonite was observed and CSH formation was found after 30 days. In hyper alkaline fluid with nitrate, minerals at θ=37 nm by XRD was identified. 2) Significant effects of hyper alkaline on hydraulic conductivity of compacted bentonite were not observed. However, hydraulic conductivities of hyper alkaline fluid with nitrate and ion exchanged bentonite increased. In hyper alkaline with nitrate, more higher hydraulic conductivities of exchanged bentonite were measured. The followings results were obtained for rock. 1) In the immersion experiments of crushed tuff in hyper alkaline fluids with and without nitrate, CSH and CASH phases were observed. 2) The hydraulic conductivity of tuff in hyper alkaline fluids decreased gradually. Finally, hyper alkaline flow in tuff stopped after 2 months and hyper alkaline flow with nitrate stopped shorter than without nitrate. In the results of analysis of tuff after experiment, we could identified secondary minerals, but we couldn't find the clogging evidence of pores in tuff by secondary minerals. (author)

  1. Evaluation of The Use of Bentonite, Kaolin and Feldspar For Immobilizing The Uranium Radionuclide Slugdewaste

    International Nuclear Information System (INIS)

    Prayitno

    2006-01-01

    The experimental investigation on the mixture of bentonite, kaolin, feldspar, sludge waste and with the ratio of bentonite, kaolin, feldspar for evaluating its effectiveness has been done. Experimentally, this investigation is the preliminary study of the use of bentonite, kaolin, feldspar as a material for the immobilization of sludge waste containing material element especially uranium. This investigation was conducted by mixing waste (2,5; 5; 7.5; 10; 12.5 and 15 %) of total weight sludge waste and bentonite, kaolin, feldspar with of 800, 900 and 1000 o C temperature. The obtained the process condition in which the uranium fraction immobilized could be kept in the limit of safety standard for the sludge waste. Therefore, it could be concluded that the addition of hay ash as an additive in the formation of block monolith tend to minimize the leached sludge waste in the leaching media. (author)

  2. Organophilic bentonites based on Argentinean and Brazilian bentonites: part 2: potential evaluation to obtain nanocomposites

    Directory of Open Access Journals (Sweden)

    L. B. Paiva

    2012-12-01

    Full Text Available This work describes the preparation of composites of polypropylene and organophilic bentonites based on Brazilian and Argentinean bentonites. During the processing of the samples in a twin screw microextruder, torque and pressures of the extruder were accompanied and the viscosity values were calculated. No significant changes in the torque, pressure and viscosity were found for composites prepared with different bentonites. The samples were characterized by XRD and TEM to evaluate the structure and dispersion of the organophilic bentonites. Composites with exfoliated, partially exfoliated and intercalated structures were obtained and correlations between the intrinsic properties of the sodium clays and organophilic bentonites and their influence on the composites were studied. The cation exchange capacity of the sodium bentonites and the swelling capacity of the organophilic bentonites were the most important properties to obtain exfoliated structures in composites. All bentonites showed the potential to obtain polymer nanocomposites, but the ones from Argentina displayed the best results.

  3. Diffusion of anions and cations in compacted sodium bentonite

    International Nuclear Information System (INIS)

    Muurinen, A.

    1994-02-01

    The thesis presents the results of studies on the diffusion mechanisms of anions and cations in compacted sodium bentonite, which is planned to be used as a buffer material in nuclear waste disposal in Finland. The diffusivities and sorption factors were determined by tracer experiments. The pore volume accessible to chloride, here defined as effective porosity, was determined as a function of bentonite density and electrolyte concentration in water, and the Stern-Gouy double-layer model was used to explain the observed anion exclusion. The sorption of Cs + and Sr 2+ was studied in loose and compacted bentonite samples as a function of the electrolyte concentration in solution. In order to obtain evidence of the diffusion of exchangeable cations, defined as surface diffusion, the diffusivities of Cs + and Sr 2+ in compacted bentonite were studied as a function of the sorption factor, which was varied by electrolyte concentration in solution. The measurements were performed both by a non-steady state method and by a through-diffusion method. (89 refs., 35 fig., 4 tab.)

  4. DEPOSITS AND MINING POTENTIAL OF BENTONITE IN CROATIA

    Directory of Open Access Journals (Sweden)

    Mario Klanfar

    2012-07-01

    Full Text Available Bentonite is one of the materials that is planed to be used for buffering and backfilling in spent nuclear fuel repositories, within deep crystalline rock. There are several locations in Croatia that bentonite deposits and occurrences are found on. Some were exploited in past, and others were more or less explored. This paper presents overview of bentonite deposits, basic properties and potential resources, and mining practices in Croatia. Largest exploited deposits are found in area of Poljanska luka, Gornja Jelenska and Bednja. Surface and underground methods (drift and fill, sublevel caving were used during exploitation. In the area of Svilaja and Lika are found potentially valuable deposits that were never exploited. Montmorilonite content ranges form 20-50% to 57-89%. Most deposits contain bentonite beds with thickness 0,4-1,6 m, and have plunge 10°-30°. Few exceptions are nearly horizontal and thick more than 5 m and even 12 m. One is declined at 70° and up to 40m thick. Proven reserves are about 2,3 Mt with some level of uncertainty. Average production per mine during exploitation period can be assumed to be several thousands t/y.

  5. Study of cesium and strontium adsorption on slovak bentonite

    International Nuclear Information System (INIS)

    Galambos, M.

    2010-01-01

    Bentonite is a natural clay and one of the most promising candidates for use as a buffer material in the geological disposal systems for high-level radioactive waste and spent nuclear fuel. It is intended to isolate metal canisters with highly radioactive waste products from the surrounding rocks because of its ability to retard the movement of radionuclides by adsorption. Slovak Republic avails of many significant deposits of bentonite. Adsorption of Cs and Sr on five Slovak bentonite of deposits (Jelsovy potok, Kopernica, Lieskovec, Lastovce and Dolna Ves) and montmorillonite K10 (Sigma-Aldrich) has been studied with the using batch of radiometric techniques. Natural, irradiated and natrified samples, in three different kinds of grain size: 15, 45 and 250 μm have been used in the experiments. The adsorptions of Cs and Sr on bentonite under various experimental conditions, such as contact time, adsorbent and adsorbate concentrations, pH after adsorption and effect of pH change, chemical modification, competitive ions and organic agents on the adsorption have been studied. The K d have been determined for adsorbent-Cs/Sr solution system as a function of contact time and adsorbate and adsorbent concentration. The data have been interpreted in terms of Langmuir isotherm. The adsorption of Cs and Sr has increased with increasing metal concentrations. Adsorption of Cs and Sr has been suppressed by presence of organic agents; and of bivalent cations more than univalent cations. By adsorption on natrified samples colloidal particles and pH value increase have been formed. Adsorption experiments carried out show that the most suitable materials intended for use as barriers surrounding a canister of spent nuclear fuel are bentonite of the Jelsovy potok and Kopernica deposits. (author)

  6. Studies on mechanical behavior of bentonite for development of the constitutive model

    International Nuclear Information System (INIS)

    Sasakura, Tsuyoshi; Kuroyanagi, Mikio; Okamoto, Michitaka

    2002-02-01

    To integrate the system for evaluation of long-term hydraulic condition in near field of TRU waste disposal, series of laboratory tests were conducted to investigate the effect of (1) cation exchange of Na-bentonite for Ca ion, and (2) the swelling behavior of bentonite, on its mechanical and hydraulic properties. For the purpose of this study, same lot of bentonite was used in a series of tests to obtain consistent data. A constitutive model of clayey materials, called Cam-clay model, was expanded conceptually to express the effects mentioned above. The research results of this year are summarized below; 1) Some basic properties such as cation exchange capacity, particle density, grain size distribution, compaction-characteristics and water content were obtained. To examine the effect of previous swelling history of bentonite on its swelling characteristics and hydraulic and mechanical properties, specimens, which generated swelling deformation to various volumetric strain levels, were specially prepared and used in the following tests. Swelling pressure tests, swelling deformation tests, permeability tests were conducted to observe one dimensional swelling characteristics and hydraulic properties of Na-bentonite and Ca-bentonite. High-pressured triaxial consolidated-undrained (CU) compression tests and high-pressured consolidation tests were also carried out to investigate the compression, swelling, and shearing behavior of each type of bentonite. 2) As indicated in previous studies, two important phenomena (1) bentonite possesses remarkable swelling capacity, (2) cation exchange of Na-bentonite for Ca-ion lead increasing of hydraulic conductivity, were confirmed in the test results. From the swelling deformation test results and published data, it was found that swelling capacity of bentonite has no dependency on previous swelling history and it could be easily expressed as a function of void ratio e. It was also confirmed that swelling pressure and water

  7. Bentonite in the repository - Manufacture of bentonite blocks. A literature study

    International Nuclear Information System (INIS)

    Hultgren, Aa.

    1995-09-01

    Activities in nuclear power countries are reviewed, concerning developments in the use of bentonite for backfilling in nuclear waste repositories, in particular regarding manufacture of bentonite-blocks. Only one report was found which in detail describes the manufacture of highly compacted blocks of bentonite. Use of bentonite for sealing boreholes etc in the oil- and gas industry was also covered in the literature study. 19 refs, 3 tabs

  8. Characterization of organo-modified bentonite sorbents: The effect of modification conditions on adsorption performance

    Energy Technology Data Exchange (ETDEWEB)

    Parolo, María E., E-mail: maria.parolo@fain.uncoma.edu.ar [Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas (PROBIEN), Facultad de Ingeniería, Universidad Nacional del Comahue, Neuquén 8300 (Argentina); Pettinari, Gisela R. [Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas (PROBIEN), Facultad de Ingeniería, Universidad Nacional del Comahue, Neuquén 8300 (Argentina); Musso, Telma B. [Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas (PROBIEN), Facultad de Ingeniería, Universidad Nacional del Comahue, Neuquén 8300 (Argentina); CONICET, Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires (Argentina); Sánchez-Izquierdo, María P.; Fernández, Laura G. [Facultad de Ingeniería, Universidad Nacional del Comahue, Neuquén 8300 (Argentina)

    2014-11-30

    Graphical abstract: - Highlights: • Modification of clay was evaluated by two methods for removing an organic substance. • Surfactant cations and organosilanes were intercalated into the interlayer space. • The hydrophobic surface of adsorbents increased the retention of organic substances. • Clay grafted with vinyltrimethoxysilane showed the highest adsorption for aniline. - Abstract: The organic modification of a natural bentonite was evaluated using two methods: exchanging the interlayer cations by hexadecyltrimethylammonium (HDTMA) and grafting with vinyltrimethoxysilane (VTMS) and γ-methacryloyloxy propyl trimethoxysilane (TMSPMA) on montmorillonite surface. The physicochemical characterization of all materials was made by X-ray diffraction (XRD), IR spectroscopy, thermogravimetric analysis (TGA) and Brunauer–Emmett–Teller (BET) surface area techniques. HDTMA cations and organosilanes were intercalated into the interlayer space of montmorillonite, as deduced from the increase of the basal spacing. IR spectroscopy, TGA and BET area give evidence of successful organic modification. The studies show a decrease in the IR absorption band intensity at 3465 cm{sup −1} with surfactant modification, and also a decrease of mass loss due to adsorbed water observed in two samples: the organoclay and functionalized bentonites, which are evidences of a lower interlayer hydrophilicity. The efficiency of aniline removal onto natural bentonite, organobentonite and functionalized bentonites from aqueous solutions was evaluated. Aniline sorption on natural bentonite was studied using batch experiments, XRD and IR spectroscopy. The hydrophobic surface of organobentonite and functionalized bentonites increased the retention capacity for nonionic organic substances such as aniline on bentonites. The sorption properties of modified bentonite, through different modification methods, enhanced the potential industrial applications of bentonites in water decontamination.

  9. Characterization of organo-modified bentonite sorbents: The effect of modification conditions on adsorption performance

    International Nuclear Information System (INIS)

    Parolo, María E.; Pettinari, Gisela R.; Musso, Telma B.; Sánchez-Izquierdo, María P.; Fernández, Laura G.

    2014-01-01

    Graphical abstract: - Highlights: • Modification of clay was evaluated by two methods for removing an organic substance. • Surfactant cations and organosilanes were intercalated into the interlayer space. • The hydrophobic surface of adsorbents increased the retention of organic substances. • Clay grafted with vinyltrimethoxysilane showed the highest adsorption for aniline. - Abstract: The organic modification of a natural bentonite was evaluated using two methods: exchanging the interlayer cations by hexadecyltrimethylammonium (HDTMA) and grafting with vinyltrimethoxysilane (VTMS) and γ-methacryloyloxy propyl trimethoxysilane (TMSPMA) on montmorillonite surface. The physicochemical characterization of all materials was made by X-ray diffraction (XRD), IR spectroscopy, thermogravimetric analysis (TGA) and Brunauer–Emmett–Teller (BET) surface area techniques. HDTMA cations and organosilanes were intercalated into the interlayer space of montmorillonite, as deduced from the increase of the basal spacing. IR spectroscopy, TGA and BET area give evidence of successful organic modification. The studies show a decrease in the IR absorption band intensity at 3465 cm −1 with surfactant modification, and also a decrease of mass loss due to adsorbed water observed in two samples: the organoclay and functionalized bentonites, which are evidences of a lower interlayer hydrophilicity. The efficiency of aniline removal onto natural bentonite, organobentonite and functionalized bentonites from aqueous solutions was evaluated. Aniline sorption on natural bentonite was studied using batch experiments, XRD and IR spectroscopy. The hydrophobic surface of organobentonite and functionalized bentonites increased the retention capacity for nonionic organic substances such as aniline on bentonites. The sorption properties of modified bentonite, through different modification methods, enhanced the potential industrial applications of bentonites in water decontamination

  10. Research program to study the gamma radiation effects in Spanish bentonites

    International Nuclear Information System (INIS)

    Dies, J.; Tarrasa, F.; Cuevas de las, C.; Miralles, L.; Pueyo, J. J.

    2000-01-01

    The engineering barrier of a radioactive waste underground disposal facility, placed in a granitic host rock, will consist of a backfill of compacted bentonite blocks. At first, this material will be subjected to a gamma radiation field, from the waste canister, and heat from the spent fuel inside the canister. Moreover, any groundwater that reaches the repository will saturate the bentonite. For these reasons the performance of the engineered barrier must be carefully assessed in laboratory experiments. (Author)

  11. Adsorption of La(III) onto GMZ bentonite. Effect of contact time, bentonite content, pH value and ionic strength

    International Nuclear Information System (INIS)

    Yonggui Chen; Changsha University of Science and Technology, Changsha; Chunming Zhu; Weimin Ye; Yanhong Sun; Huiying Duan; Dongbei Wu

    2012-01-01

    Bentonite has been studied extensively because of its strong adsorption capacity. A local Na-bentonite named GMZ bentonite, collected from Gaomiaozi County (Inner Mongolia, China), was selected as the first choice of buffer/backfill material for the high-level radioactive waste repository in China. In this research, the adsorption of La (III) onto GMZ bentonite was performed as a function of contact time, pH, solid content and metal ion concentrations by using the batch experiments. The results indicate that the adsorption of La (III) on GMZ bentonite achieves equilibration quickly and the kinetic adsorption follows the pseudo-second-order model; the adsorption of La (III) on the adsorbent is strongly dependent on pH and solid content, the adsorption process follows Langmuir isotherm. The equilibrium batch experiment data demonstrate that GMZ bentonite is effective adsorbent for the removal of La (III) from aqueous solution with the maximum adsorption capacity of 26.8 mg g -1 under the given experimental conditions. (author)

  12. Roles of bentonite in radioactive waste disposal

    International Nuclear Information System (INIS)

    Suzuki, Keizo

    1995-01-01

    Bentonite is used in radioactive waste disposal from the following points; (1) properties (2) now utilization fields (3) how to use in radioactive waste disposal (4) how much consumption and deposits as source at the present time. Bentonite is produced as alteration products from pyroclastic rocks such as volcanic ash and ryolite, and is clay composed mainly smectite (montmorillonite in general). Therefore, special properties of bentonite such as swelling potential, rheological property, bonding ability, cation exchange capacity and absorption come mainly from properties of montmorillonite. Bentonite has numerous uses such as iron ore pelleizing, civil engineering, green sand molding, cat litter, agricultural chemicals and drilling mud. Consumption of bentonite is about 600-700 x 10 3 tons in Japan and about 10 x 10 6 tons in the world. Roles of bentonite to be expected in radioactive waste disposal are hydraulic conductivity, swelling potential, absorption, mechanical strength, ion diffusion capacity and long-term durability. These properties come from montmorillonite. (author)

  13. Size-induced axial band structure and directional flow of a ternary-size granular material in a 3-D horizontal rotating drum

    Science.gov (United States)

    Yang, Shiliang; Sun, Yuhao; Ma, Honghe; Chew, Jia Wei

    2018-05-01

    Differences in the material property of the granular material induce segregation which inevitably influences both natural and industrial processes. To understand the dynamical segregation behavior, the band structure, and also the spatial redistribution of particles induced by the size differences of the particles, a ternary-size granular mixture in a three-dimensional rotating drum operating in the rolling flow regime is numerically simulated using the discrete element method. The results demonstrate that (i) the axial bands of the medium particles are spatially sandwiched in between those of the large and small ones; (ii) the total mass in the active and passive regions is a global parameter independent of segregation; (iii) nearly one-third of all the particles are in the active region, with the small particles having the highest mass fraction; (iv) the axial bands initially appear near the end wall, then become wider and purer in the particular species with time as more axial bands form toward the axial center; and (v) the medium particle type exhibits segregation later and has the narrowest axial bandwidth and least purity in the bands. Compared to the binary-size system, the presence of the medium particle type slightly increases the total mass in the active region, leads to larger mass fractions of the small and large particle types in the active region, and enhances the axial segregation in the system. The results obtained in the current work provide valuable insights regarding size segregation, and band structure and formation in the rotating drum with polydisperse particles.

  14. Granular corneal dystrophy

    OpenAIRE

    Castillo Pérez, Alexeide de la C; Vilches Lescaille, Daysi; Noriega, Justo Luis; Martínez Balido, Daneel; León Balbón, Bárbaro Ramón; León Bernal, Danysleidi

    2015-01-01

    Las distrofias corneales constituyen un conjunto de enfermedades que presentan, en su mayoría, una baja incidencia y se caracterizan por acúmulo de material hialino o amiloide que disminuyen la transparencia corneal. La distrofia granular es una enfermedad autosómica dominante que presenta opacidades grises en el estroma superficial central de la córnea y se hacen visibles en la primera y segunda décadas de la vida, lo que provoca disminución de la visión más significativa cerca de los 40 año...

  15. Diffusion of uranium in compacted sodium bentonite

    International Nuclear Information System (INIS)

    Muurinen, A.; Lehikoinen, J.

    1992-09-01

    In the study the diffusion of uranium dissolved from uranium oxide fuel was studied experimentally in compacted sodium bentonite (Wyoming bentonite MX-80). The experiments were carried out by the through-diffusion method. The parameters varied in the study were the density of bentonite, salt content of the solution and redox conditions. Uranium was dissolved under aerobic conditions in order to simulate oxic conditions possibly caused by radiolysis in the repository

  16. Alteration of bentonite when contacted with supercritical CO2

    Science.gov (United States)

    Jinseok, K.; Jo, H. Y.; Yun, S. T.

    2014-12-01

    Deep saline formations overlaid by impermeable caprocks with a high sealing capacity are attractive CO2 storage reservoirs. Shales, which consist of mainly clay minerals, are potential caprocks for the CO2 storage reservoirs. The properties of clay minerals in shales may affect the sealing capacity of shales. In this study, changes in clay minerals' properties when contacted with supercritical (SC) CO2 at various conditions were investigated. Bentonite, whichis composed of primarily montmorillonite, was used as the clay material in this study. Batch reactor tests on wet bentonite samples in the presence of SC CO2 with or without aqueous phases were conducted at high pressure (12 MPa) and moderate temperature (50 oC) conditions for a week. Results show that the bentonite samples obtained from the tests with SC CO2 had less change in porosity than those obtained from the tests without SC CO2 (vacuum-drying) at a given reaction time, indicating that the bentonite samples dried in the presence of SC CO2 maintained their structure. These results suggest that CO2 molecules can diffuse into interlayer of montmorillonite, which is a primary mineral of bentonite, and form a single CO2 molecule layer or double CO2 molecule layers. The CO2 molecules can displace water molecules in the interlayer, resulting in maintaining the interlayer spacing when dehydration occurs. Noticeable changes in reacted bentonite samples obtained from the tests with an aqueous phase (NaCl, CaCl2, or sea water) are decreases in the fraction of plagioclase and pyrite and formation of carbonate minerals (i.e., calcite and dolomite) and halite. In addition, no significant exchanges of Na or Ca on the exchangeable complex of the montmorillonite in the presence of SC CO2 occurred, resulting in no significant changes in the swelling capacity of bentonite samples after reacting with SC CO2 in the presence of aqueous phases. These results might be attributed by the CO2 molecule layer, which prevents

  17. Uncertainties in pore water chemistry of compacted bentonite from Rokle deposit

    International Nuclear Information System (INIS)

    Cervinka, R.; Vejsadu, J.; Vokal, A.

    2012-01-01

    Document available in extended abstract form only. The composition of compacted bentonite pore water influences a number of important processes occurring in a deep geological repository (DGR), e.g. corrosion of waste package materials, solubility of radionuclides, or diffusion and sorption of radionuclides. Its determination is not straightforward, because it is difficult to obtain (e.g. squeeze) the pore water from compacted bentonite without changing its properties. It is therefore necessary to combine experimentally obtained parameters and geochemical modelling to approach it compositions. This article describes the results achieved in investigation the composition of pore water of compacted Ca-Mg bentonite from Czech deposits, proposed in Czech DGR concept. Ca-Mg bentonite from the largest operating deposit Rokle (Tertiary neo-volcanic area, NW Bohemia) represents complex mixture of (Ca,Mg)-Fe-rich montmorillonite, micas, kaolinite and other mineral admixtures (mainly Ca, Mg, Fe carbonates, feldspars and iron oxides). For experimental investigations the homogenized and grind raw bentonite material obtained directly from the deposit and commercial product (partly Na-activated) from supplier were used. Geochemical characterization of Rokle bentonite included mineralogical composition analyzed by Xray diffraction, cation exchange capacity determined using Cu-trien method, surface complexation parameters determined by acid-base titrations and 'geochemical' porosity derived from diffusion experiments with tracers ( 3 H and 36 Cl). Soluble salts inventory was calculated on the base of results from aqueous extracts of bentonite in deionized water at different solid to liquid ratios (from 18.6 to 125 g/l) and high pressure squeezing of water saturated bentonite at different solid to liquid ratios (from 1:1 to 4:1 w/w). The geochemical model contained cation exchange in the interlayer space and protonization and de-protonization of surface hydroxyl groups on clay

  18. Cement/bentonite interaction. Results from 16 month laboratory tests

    Energy Technology Data Exchange (ETDEWEB)

    Karnland, O. [Clay Technology AB, Lund (Sweden)

    1997-12-01

    The work concerns possible bentonite clay mineral alteration in constructions with bentonite in close contact with cement, and the effect of such changes on bentonite buffer properties. The investigation comprises a 16 months laboratory test series with hydrothermal cell tests, percolation tests and diffusion tests. MX-80 Wyoming bentonite was used in all tests. Two types of artificial cement pore water solutions were used in the percolation and diffusion tests. The swelling pressure and the hydraulic conductivity were measured continuously in the percolation tests. After termination, the clay was analyzed with respect to changes in element distribution, mineralogy and shear strength. The water solutions were analyzed with respect to pH, cations and major anions. The results concerning chemical and mineralogical changes are in summary: Ion exchange in the montmorillonite until equilibrium with cement pore-water ions was reached; Increase in cation exchange capacity; Dissolution of original cristobalite; Increase in quartz content; Minor increase in illite content; Minor formation of chlorite; Formation of CSH(I); Wash away of CSH-gel into surrounding water. A large decrease in swelling pressure and a moderate increase in hydraulic conductivity were recorded in the samples percolated by SULFACEM pore-water solution. The mineralogical alterations only concerned a minor part of the total bentonite mass and the changes in physical properties were therefore most likely due to the replacement of the original charge balancing cation by cement pore-water cations. Comparisons between the current test result and results from 4 month tests indicate that the rates of illite and chlorite formation were reduced during the tests. The presence of zeolites in the clay could not be ensured. However, the discovery of CSH material is important since CSH is expected to precede the formation of zeolites 5 refs, 48 figs, 11 tabs

  19. Thermodynamic understanding on swelling pressure of bentonite buffer

    International Nuclear Information System (INIS)

    Sato, Haruo

    2007-01-01

    Smectite (montmorillonite) is a major clay mineral constituent of the bentonite buffer and backfilling materials to be used for the geological disposal of high-level radioactive waste. Swelling pressure of the bentonite buffer occurring in the permeation process of moisture was estimated based on thermodynamic theory and the thermodynamic data of interlayer water in smectite in this study. The relative partial molar Gibbs free energies (ΔG H2O ) of water on the smectite surface were measured as a function of water content (0-83%) in a dry density range of 0.6-0.9 Mg/m 3 . Purified Na-smectite of which interlayer cations were exchanged with Na + ions and soluble salts were completely removed, was used in this study. Obtained ΔG H2O decreased with an increase of water content in the range of water content lower than about 40%, and similar trends were obtained to data of Kunipia-F bentonite (Na-bentonite) of which smectite content was approximately 100 wt.%. From the specific surface area of smectite (ca. 800 m 2 /g) and the correlation between ΔG H2O and water content, water affected from the surface of smectite was estimated to be up to approximately 2 water layers. Swelling pressure versus smectite partial density (montmorillonite partial density) was estimated based on ΔG H2O from the chemical potential balance of water in equilibrium between the free water and moisturized smectite, and compared to data measured for various kinds of bentonites of which smectite contents were respectively different. The estimated swelling pressures were in good agreement with the measured data. (author)

  20. Two-phase modeling of deflagration-to-detonation transition in granular materials: A critical examination of modeling issues

    International Nuclear Information System (INIS)

    Bdzil, J.B.; Menikoff, R.; Son, S.F.; Kapila, A.K.; Stewart, D.S.

    1999-01-01

    The two-phase mixture model developed by Baer and Nunziato (BN) to study the deflagration-to-detonation transition (DDT) in granular explosives is critically reviewed. The continuum-mixture theory foundation of the model is examined, with particular attention paid to the manner in which its constitutive functions are formulated. Connections between the mechanical and energetic phenomena occurring at the scales of the grains, and their manifestations on the continuum averaged scale, are explored. The nature and extent of approximations inherent in formulating the constitutive terms, and their domain of applicability, are clarified. Deficiencies and inconsistencies in the derivation are cited, and improvements suggested. It is emphasized that the entropy inequality constrains but does not uniquely determine the phase interaction terms. The resulting flexibility is exploited to suggest improved forms for the phase interactions. These improved forms better treat the energy associated with the dynamic compaction of the bed and the single-phase limits of the model. Companion papers of this study [Kapila et al., Phys. Fluids 9, 3885 (1997); Kapila et al., in preparation; Son et al., in preparation] examine simpler, reduced models, in which the fine scales of velocity and pressure disequilibrium between the phases allow the corresponding relaxation zones to be treated as discontinuities that need not be resolved in a numerical computation. copyright 1999 American Institute of Physics

  1. Swelling and hydraulic properties of Ca-bentonite for the buffer of a waste repository

    International Nuclear Information System (INIS)

    Lee, J.O.; Cho, W.J.; Kang, C.H.; Chun, K.S.

    2001-01-01

    Swelling and hydraulic tests were carried out to provide the information for the selection of buffer material in a radioactive waste repository. Ca-bentonite and de-ionized water were used for the tests. The swelling pressures of compacted bentonite were in the wide range of 0.7 Kg/cm 2 to 190.2 Kg/cm 2 , and they largely increased with an increase in the dry density and bentonite content. However, the swelling pressures decreased with increasing the initial water content and beyond about 12 wt.% of the initial water content, leveled off to a nearly constant value. The hydraulic conductivities were lower than 10 -11 m/s for the compacted bentonite with the dry density higher than 1.4 Mg/m 3 . They increased with increasing temperature in the range of 20 deg. C to 150 deg. C. (author)

  2. Thermally modified bentonite clay for copper removal

    International Nuclear Information System (INIS)

    Bertagnolli, C.; Kleinübing, S.J.; Silva, M.G.C.

    2011-01-01

    Bentonite clay coming from Pernambuco was thermally modified in order to increase its affinity and capacity in the copper removal in porous bed. The application of this procedure is justified by the low cost of clay, their abundance and affinity for various metal ions. Thermally treatment modifies the clay adsorption properties enables its use in porous bed system, with the increase in surface area and mechanical strength. The material was characterized by x-ray diffraction, thermogravimetric analysis and N_2 physisorption. Then tests were carried out for adsorption of copper in various experimental conditions and evaluated the mass transfer zone, useful and total adsorbed removal amounts and total copper removal percentage. The results showed that the clay treated at higher temperature showed higher copper removal. (author)

  3. Development of spraying methods for high density bentonite barriers. Part 3. Field investigation of spraying methods

    International Nuclear Information System (INIS)

    Tanaka, Toshiyuki; Nakajima, Makoto; Kobayashi, Ichizo; Toida, Masaru; Fukuda, Katsumi; Sato, Tatsuro; Nonaka, Katsumi; Gozu, Keisuke

    2007-01-01

    The authors have developed a new method of constructing high density bentonite barriers by means of a wet spraying method. Using this method, backfill material can be placed in narrow upper and side parts in a low-level radioactive waste disposal facility. Using a new supplying machine for bentonite, spraying tests were conducted to investigate the conditions during construction. On the basis of the test results, the various parameters for the spraying method were investigated. The test results are summarized as follows: 1. The new machine supplied about twice the weight of material supplied by a screw conveyor. A dry density of spraying bentonite 0.05 Mg/m 3 higher than that of a screw conveyor with the same water content could be achieved. 2. The dry density of sprayed bentonite at a boundary with concrete was the same as that at the center of the cross section. 3. The variation in densities of bentonite sprayed in the vertical downward and horizontal directions was small. Also, density reduction due to rebound during spraying was not seen. 4. Bentonite controlled by water content could be sprayed smoothly in the horizontal direction by a small machine. Also rebound could be collected by a machine conveying air. (author)

  4. CRIEPI's research results (2006-2011) and clarified future issues on alteration behavior of bentonite barrier by alkaline solutions

    International Nuclear Information System (INIS)

    Yokoyama, Shingo; Nakamura, Kunihiko; Tanaka, Yukihisa; Hironaga, Michihiko

    2013-01-01

    In radioactive waste disposal facilities, bentonite barrier would be altered by alkaline solutions which arise by leaching of cementitious materials. Consequently suitable properties of the bentonite barrier would be degraded for a long time period. In CRIEPI, the investigation on the alteration of the bentonite under alkaline conditions was started in 2006, and several CRIEPI reports have been published. Specifically, we have investigated the kinetics of montmorillonite dissolution, the mineralogical alteration of compacted bentonite (with high- and low-dry density) and the change of permeability of the compacted bentonite (with high- and low-dry density) during alteration under the alkaline conditions. Furthermore, stability of saponite, which has similar physical properties to the bentonite, under the alkaline conditions was also examined. In this report, we show the outline of those research results, and lay out the clarified future issues extracted from our results. Ten clarified future issues were divided three categories as follows: 1) the estimation of the alteration behavior of the bentonite by alkaline solutions, 2) the elucidation of the mechanism of physical properties (e.g., permeability, swelling properties and mechanistic properties) change of the compacted bentonites during alteration, and 3) the development of the model building and simulation technology concerning the change in physical properties during alteration under alkaline conditions. (author)

  5. Thermo-hydro-geochemical modelling of the bentonite buffer. LOT A2 experiment

    Energy Technology Data Exchange (ETDEWEB)

    Sena, Clara; Salas, Joaquin; Arcos, David (Amphos 21 Consulting S.L., Barcelona (Spain))

    2010-12-15

    The Swedish Nuclear Fuel and waste management company (SKB) is conducting a series of long term buffer material (LOT) tests at the Aespoe Hard Rock Laboratory (HRL) to test the behaviour of the bentonite buffer under conditions similar to those expected in a KBS-3 deep geological repository for high level nuclear waste (HLNW). In the present work a numerical model is developed to simulate (i) the thermo-hydraulic, (ii) transport and (iii) geochemical processes that have been observed in the LOT A2 test parcel. The LOT A2 test lasted approximately 6 years, and consists of a 4 m long vertical borehole drilled in diorite rock, from the ground of the Aespoe HRL tunnel. The borehole is composed of a central heater, maintained at 130 deg C in the lower 2 m of the borehole, a copper tube surrounding the heater and a 100 mm thick ring of pre-compacted Wyoming MX-80 bentonite around the copper tube /Karnland et al. 2009/. The numerical model developed here is a 1D axis-symmetric model that simulates the water saturation of the bentonite under a constant thermal gradient; the transport of solutes; and, the geochemical reactions observed in the bentonite blocks. Two cases have been modelled, one considering the highest temperature reached by the bentonite (at 3 m depth in the borehole, where temperatures of 130 and 85 deg C have been recorded near the copper tube and near the granitic host rock, respectively) and the other case assuming a constant temperature of 25 deg C, representing the upper part of borehole, where the bentonite has not been heated. In the LOT A2 test, the initial partially saturated bentonite becomes progressively water saturated, due to the injection of Aespoe granitic groundwater at granite - bentonite interface. The transport of solutes during the bentonite water saturation stage is believed to be controlled by water uptake from the surrounding groundwater to the wetting front and, additionally, in the case of heated bentonite, by a cyclic evaporation

  6. Thermo-hydro-geochemical modelling of the bentonite buffer. LOT A2 experiment

    International Nuclear Information System (INIS)

    Sena, Clara; Salas, Joaquin; Arcos, David

    2010-12-01

    The Swedish Nuclear Fuel and waste management company (SKB) is conducting a series of long term buffer material (LOT) tests at the Aespoe Hard Rock Laboratory (HRL) to test the behaviour of the bentonite buffer under conditions similar to those expected in a KBS-3 deep geological repository for high level nuclear waste (HLNW). In the present work a numerical model is developed to simulate (i) the thermo-hydraulic, (ii) transport and (iii) geochemical processes that have been observed in the LOT A2 test parcel. The LOT A2 test lasted approximately 6 years, and consists of a 4 m long vertical borehole drilled in diorite rock, from the ground of the Aespoe HRL tunnel. The borehole is composed of a central heater, maintained at 130 deg C in the lower 2 m of the borehole, a copper tube surrounding the heater and a 100 mm thick ring of pre-compacted Wyoming MX-80 bentonite around the copper tube /Karnland et al. 2009/. The numerical model developed here is a 1D axis-symmetric model that simulates the water saturation of the bentonite under a constant thermal gradient; the transport of solutes; and, the geochemical reactions observed in the bentonite blocks. Two cases have been modelled, one considering the highest temperature reached by the bentonite (at 3 m depth in the borehole, where temperatures of 130 and 85 deg C have been recorded near the copper tube and near the granitic host rock, respectively) and the other case assuming a constant temperature of 25 deg C, representing the upper part of borehole, where the bentonite has not been heated. In the LOT A2 test, the initial partially saturated bentonite becomes progressively water saturated, due to the injection of Aespoe granitic groundwater at granite - bentonite interface. The transport of solutes during the bentonite water saturation stage is believed to be controlled by water uptake from the surrounding groundwater to the wetting front and, additionally, in the case of heated bentonite, by a cyclic evaporation

  7. E-learning Materials Development: Applying and Implementing Software Reuse Principles and Granularity Levels in the Small

    OpenAIRE

    Nabil Arman

    2010-01-01

    E-learning materials development is typically acknowledged as an expensive, complicated, and lengthy process, often producing materials that are of low quality and difficult to adaptand maintain. It has always been a challenge to identify proper e-learning materials that can be reused at a reasonable cost and effort. In this paper, software engineering reuse principlesare applied to e-learning materials development process. These principles are then applied and implemented in a prototype that...

  8. Advanced Granular System Modeling, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Spaceports of the future will utilize new granular materials in unique applications including insulation for cryogenic tanks and Lunar regolith processing for usable...

  9. Stress-strain relation of bentonite at undrained shear. Laboratory tests to investigate the influence of material composition and test technique

    Energy Technology Data Exchange (ETDEWEB)

    Dueck, Ann; Boergesson, Lennart; Johannesson, Lars-Erik (Clay Technology AB, Lund (Sweden))

    2010-12-15

    This report describes a laboratory study conducted to update the material model of the buffer material used in the analyses of the effect of a rock shear through a deposition hole. The study considers some new conditions and is especially focused on the reference case with MX-80Ca developed for SR-Site (MX-80 ion exchanged to Ca). The material model is based on relations between density, swelling pressure, shear strength and rate of strain. The reference model is described by Boergesson et al. (2010). The laboratory study is focused on undrained stress-strain-strength properties, which have been studied mainly by conducting triaxial tests and unconfined compression tests. The test results are compared to the earlier measurements and models which show that the new results fit very well into the general picture and models. For the new conditions suitable values of constants included in the model are proposed

  10. Stress-strain relation of bentonite at undrained shear. Laboratory tests to investigate the influence of material composition and test technique

    International Nuclear Information System (INIS)

    Dueck, Ann; Boergesson, Lennart; Johannesson, Lars-Erik

    2010-12-01

    This report describes a laboratory study conducted to update the material model of the buffer material used in the analyses of the effect of a rock shear through a deposition hole. The study considers some new conditions and is especially focused on the reference case with MX-80Ca developed for SR-Site (MX-80 ion exchanged to Ca). The material model is based on relations between density, swelling pressure, shear strength and rate of strain. The reference model is described by Boergesson et al. (2010). The laboratory study is focused on undrained stress-strain-strength properties, which have been studied mainly by conducting triaxial tests and unconfined compression tests. The test results are compared to the earlier measurements and models which show that the new results fit very well into the general picture and models. For the new conditions suitable values of constants included in the model are proposed

  11. Aplicação da alvenaria estrutural em sistemas de armazenamento de produtos agrícolas a granel Applying structural masonry for granular material storage systems

    Directory of Open Access Journals (Sweden)

    José F. de A Marques Neto

    2011-02-01

    Full Text Available O armazenamento de produtos agrícolas cumpre um papel importante no agronegócio. Observa-se uma tendência cada vez maior em se trabalhar com produtos a granel, em grandes volumes. Visando a uma concepção construtiva racional e econômica, o presente trabalho propõe um sistema misto em concreto armado e alvenaria estrutural aplicado a silos para armazenagem de produto agrícola a granel. No projeto proposto, o silo é composto de células em alvenaria estrutural, geminadas duas a duas na largura e com um número variável de células no comprimento, em função do volume desejado de armazenagem. Esse sistema simétrico favorece a racionalidade operacional, garantindo a continuidade entre os fluxos de recebimento e de expedição. O fundo da célula é em forma de tremonha dupla troncopiramidal, com saída central, construída em painéis treliçados pré-moldados. A sustentação das células e das tremonhas é feita através de vigas e de pilares de concreto armado. O isolamento térmico necessário para que a qualidade do produto armazenado seja garantida é estabelecido pela utilização de telhas trapezoidais de aço galvanizado, tanto na cobertura como nos fechamentos laterais. A fim de ilustrar o presente trabalho, um exemplo de silo utilizando o sistema proposto é apresentado, e a viabilidade da concepção construtiva adotada é analisada.The storage of granular materials has had an important role in the agribusiness. Storing granular materials in silos, instead of in bags or big-bags, has been an increase tendency. Aiming at an economic and rational solution for storing granular materials this paper presents an alternative design: a multi-cell silo group composed of reinforced masonry rectangular cells coupled two by two in width, and a variable number of cells in length according to the volume of desired storage. Such symmetrical system benefits the loading and the unloading operations, and guarantees the continuity between the

  12. An Evaluation of the Resilient Modulus and Permanent Deformation of Unbound Mixtures of Granular Materials and Rubber Particles from Scrap Tyres to Be Used in Subballast Layers

    Energy Technology Data Exchange (ETDEWEB)

    Hidalgo Sgnes, C.

    2016-07-01

    Over the last years rubber from scrap tyres has been reused in different civil works such as road embankments and railway platforms due to its resilient properties, low degradation and vibration attenuation. Unfortunately, this issue is still scarce. For instance, in Spain about 175.000 tonnes of scrap tyres were collected in 2014, of which only 0.6% were reused in civil works. Aiming to contribute to the reutilisation of large quantities of this waste material, this paper focuses on the analysis of unbound mixtures of granular materials with different percentages of rubber particles to be used as subballast layers. Mixtures are tested under cyclic triaxial tests so as to obtain their resilient modulus and evaluate their permanent deformations. It is found that as the rubber content increases, the resilient modulus decreases and the permanent deformation increases. Taking into account the usual loads transmitted to the subballast layer, the optimum rubber content that does not compromise the behaviour of the mixture is set in a range between 2.5% and 5% in terms of weight. (Author)

  13. Monitoring of bentonite pore water with a probe based on solid-state microsensors

    International Nuclear Information System (INIS)

    Orozco, Jahir; Baldi, Antoni; Martin, Pedro L.; Bratov, Andrei; Jimenez, Cecilia

    2006-01-01

    Repositories for the disposal of radioactive waste generally rely on a multi-barrier system to isolate the waste from the biosphere. This multi-barrier system typically comprises Natural geological barrier provided by the repository host rock and its surroundings and an engineered barrier system (EBS). Bentonite is being studied as an appropriated porous material for an EBS to prevent or delay the release and transport of radionuclides towards biosphere. The study of pore water chemistry within bentonite barriers will permit to understand the transport phenomena of radionuclides and obtain a database of the bentonite-water interaction processes. In this work, the measurement of some chemical parameters in bentonite pore water using solid-state microsensors is proposed. Those sensors are well suited for this application since in situ measurements are feasible and they are robust enough for the long periods of time that monitoring is needed in an EBS. A probe containing an ISFET (ion sensitive field effect transistor) for measuring pH, and platinum microelectrodes for measuring conductivity and redox potential was developed, together with the required instrumentation, to study the chemical changes in a test cell with compacted bentonite. Response features of the sensors' probe and instrumentation performance in synthetic samples with compositions similar to those present in bentonite barriers are reported. Measurements of sensors stability in a test cell are also presented

  14. The Use of Modified Bentonite for Removal of Aromatic Organics from Contaminated Soil.

    Science.gov (United States)

    Gitipour; Bowers; Bodocsi

    1997-12-15

    This study investigates the clay-aromatic interactions with a view to the use of bentonite clay for binding benzene, toluene, ethylbenzene, and o-xylene (BTEX compounds) in contaminated soils. BTEX compounds are the most toxic aromatic constituents of gasoline present in many underground storage tanks. Modified (organophilic) and ordinary bentonites are used to remove these organics. The organophilic bentonites are prepared by replacing the exchangeable inorganic cations present in bentonite particles with a quaternary ammonium salt. Various clay-to-soil ratios were applied to determine the efficiency of the modified bentonite in enhancing the cement-based solidification/stabilization (S/S) of BTEX contaminated soils. Toxicity characteristics leaching procedure (TCLP) tests were performed on soil samples to evaluate the leaching of the organics. In addition, X-ray diffraction analyses were conducted to assess the changes in the basal spacing of the clays as a result of their interaction with BTEX compounds. The findings of this study reveal that organophilic bentonite can act as a successful adsorbent for removing the aromatic organics from contaminated soil. Thus, this material is viable for enhancing the performance of cement-based S/S processes, as an adsorbent for petroleum spills, and for landfill liners and slurry walls. Copyright 1997 Academic Press.

  15. The use of modified bentonite for removal of aromatic organics from contaminated soil

    International Nuclear Information System (INIS)

    Gitipour, S.; Bowers, M.T.; Bodocsi, A.

    1997-01-01

    This study investigates the clay-aromatic interactions with a view to the use of bentonite clay for binding benzene, toluene, ethylbenzene, and o-xylene (BTEX compounds) in contaminated soils. BTEX compounds are the most toxic aromatic constituents of gasoline present in many underground storage tanks. Modified (organophilic) and ordinary bentonites are used to remove these organics. The organophilic bentonites are prepared by replacing the exchangeable inorganic cations present in bentonite particles with a quaternary ammonium salt. Various clay-to-soil ratios were applied to determine the efficiency of the modified bentonite in enhancing the cement-based solidification/stabilization (S/S) of BTEX contaminated soils. Toxicity characteristics leaching procedure (TCLP) tests were performed on soil samples to evaluate the leaching of the organics. In addition, X-ray diffraction analyses were conducted to assess the changes in the basal spacing of the clays as a result of their interaction with BTEX compounds. The findings of this study reveal that organophilic bentonite can act as a successful adsorbent for removing the aromatic organics from contaminated soil. Thus, this material is viable for enhancing the performance of cement-based S/S processes, as an adsorbent for petroleum spills, and for landfill liners and slurry walls

  16. Strain localisation in granular media

    OpenAIRE

    Desrues , Jacques

    1984-01-01

    This study is devoted to strain localisation in Granular materials. Both experimental and theoretical results have been obtained.The first part of the thesis is a review of the methods and theories about rupture in sols mechanics and more generally, in solid mechanics. The classical framework of Shear Band analysis is presented, and the main results available for different classes of materials are discussed.The second part describes an experimental study of strain localisation in sand specime...

  17. Saturation of bentonite dependent upon temperature

    International Nuclear Information System (INIS)

    Hausmannova, Lucie; Vasicek, Radek

    2010-01-01

    Document available in extended abstract form only. The fundamental idea behind the long-term safe operation of a deep repository is the use of the Multi-barrier system principle. Barriers may well differ according to the type of host rock in which the repository is located. It is assumed that the buffer in the granitic host rock environment will consist of swelling clays which boast the ideal properties for such a function i.e. low permeability, high swelling pressure, self-healing ability etc. all of which are affected primarily by mineralogy and dry density. Water content plays a crucial role in the activation of swelling pressure as well as, subsequently, in the potential self healing of the various contact areas of the numerous buffer components made from bentonite. In the case of a deep repository, a change in water content is not only connected with the possible intake of water from the host rock, but also with its redistribution owing to changes in temperature after the insertion of the heat source (disposal waste package containing spent fuel) into the repository 'nest'. The principal reason for the experimental testing of this high dry density material is the uncertainty with regard to its saturation ability (final water content or the degree of saturation) at higher temperatures. The results of the Mock-Up-CZ experiment showed that when the barrier is constantly supplied with a saturation medium over a long time period the water content in the barrier as well as the degree of saturation settle independently of temperature. The Mock-Up-CZ experiment was performed at temperatures of 30 deg. - 90 deg. C in the barrier; therefore it was decided to experimentally verify this behaviour by means of targeted laboratory tests. A temperature of 110 deg. C was added to the set of experimental temperatures resulting in samples being tested at 25 deg. C, 95 deg. C and 110 deg. C. The degree of saturation is defined as the ratio of pore water volume to pore

  18. Permeability of highly compacted bentonite

    International Nuclear Information System (INIS)

    Pusch, R.

    1980-12-01

    The object of the study was the water flow through the bentonite which is caused by hydraulic gradients. The study comprised laboratory tests and theoretical considerations. It was found that high bulk densities reduced the permeability to very low values. It was concluded that practically impervious conditions prevail when the gradients are low. Thus with a regional gradient of 10 -2 and a premeability of 10 -13 m/s the flow rate will not be higher than approximately 1 mm in 30 000 years. (G.B.)

  19. Rheological characterization of nanocomposites Nylon 6/bentonite clay

    International Nuclear Information System (INIS)

    Silva, T.R.G.; Fernandes, P.C.; Oliveira, S.V.; Araujo, E.M.; Melo, T.J.A.

    2010-01-01

    Polymer nanocomposites are a class of materials that have been widely used in various applications. Among them, has been emphasizing the preparation of polymer films with barrier properties for applications in polymer membranes. In this work, nanocomposites of nylon 6/bentonite clay were obtained from a Homogenizer, in the ratios of 1, 3 and 5 wt% clay. The Brasgel PA bentonite clay was treated organically with Praepagen HY salt, to make it organophilic. By X-ray diffraction (XRD), it was showed that the efficiency of the incorporation of salt in the clay. The rheological curves showed that for the AST clay the torque did not change when compared with the pure nylon 6, while for the clay ACT, the torque increased gradually with the percentage of clay. (author)

  20. LABORATORY TESTING OF BENTONITE CLAYS FOR LANDFILL DESIGN AND CONSTRUCTION

    Directory of Open Access Journals (Sweden)

    Biljana Kovačević Zelić

    2007-12-01

    Full Text Available Top and bottom liners are one of the key construction elements in every landfill. They are usually made as compacted clay liners (CCLs composed of several layers of compacted clay with strictly defined properties or by the use of alternative materials such as: GCL – geosynthetic clay liner, BES – bentonite enhanced soils or bentonite/polymer mixtures. Following the state of the art experiences in the world, GCLs are used in Croatian landfills for several years, as well. Depending upon the location and the obeying function, GCLs have to fulfill certain conditions. A legislated compatibility criterion has to be proven by various laboratory tests. In the paper are presented the results of direct shear and chemical compatibility tests of GCLs as well as the results of permeability measurement of kaolin clay (the paper is published in Croatian .

  1. Development of construction methods for high-density bentonite barriers using premixed spraying. Part 1. Laboratory tests on methods of spraying roughly crushed bentonite and investigation of mixing methods

    International Nuclear Information System (INIS)

    Kobayashi, Ichizo; Tanaka, Toshiyuki; Nakajima, Makoto; Toida, Masaru

    2006-01-01

    According to the present concept of geological disposal of radioactive waste, a disposal facility should consist of a bentonite-engineered barrier, a cementitious-engineered barrier, and natural barriers. To guarantee the validity of the geological disposal concept, the bentonite-engineered barrier must have high impermeability. However, an effective construction method for high-density bentonite-engineered barriers in narrow spaces such as those in radioactive waste geological disposal sites has not been developed. Therefore, the authors have developed a spraying method that has high workability in narrow spaces as a method of constructing bentonite-engineered barriers in narrow spaces. This paper describes the production method for a spraying material and an examination through spraying tests of the spraying distance, the shapes of the spray nozzles, and the ratio of spraying material to air. The test results confirmed that a bentonite-engineered barrier of dry density 1.6 Mg/m 3 could be constructed using the spraying method developed and that the appropriate spraying conditions for the construction of high-density bentonite barriers were obtained. Moreover, the authors developed a construction quality management method using the silicon oil specific-gravity method that can clearly and promptly indicate the dry density of the sprayed bentonite. (author)

  2. Diffusion of radionuclides in concrete/bentonite systems

    International Nuclear Information System (INIS)

    Albinsson, Y.; Boerjesson, S.; Andersson, K.; Allard, B.

    1993-02-01

    In a repository for nuclear waste, different construction materials will be used. Two important materials among these are concrete and bentonite clay. These will act as mechanical barriers, preventing convective water flow and also retard transport due to diffusion of dissolved radionuclides by a combination of mechanical constraints and chemical interactions with the solid. An important issue is the possible change of the initial sodium bentonite into the calcium form due to ion exchange with calcium from the cement. The initial leaching of the concrete has been studied using radioactive spiked concrete in contact with compacted bentonite. The diffusion of Cs, Am and Pu into 5 different types of concrete in contact with porewater have been measured. The measured diffusivity for Cs agrees reasonable well with data found in literature. For Am and Pu no movement could be measured (less than 0.2 mm) even though the contact times were extremely long (2.5 y and 5 y, respectively). This report gives also a summary of the previously published results about sorption and diffusion of radionuclides in cement performed in Prav/KBS/SKB projects 1980-1990. 25 refs

  3. Use of municipal solid waste incineration bottom ashes in alkali-activated materials, ceramics and granular applications: A review.

    Science.gov (United States)

    Silva, R V; de Brito, J; Lynn, C J; Dhir, R K

    2017-10-01

    This paper presents a literature review on the incorporation of municipal solid waste incinerated bottom ash as raw material in several markets, other than those where it is conventionally used, such as geotechnical applications and road pavement construction. The main findings of an ample selection of experimental investigations on the use of the bottom ash as precursor of alkali-activated materials, as an adsorbent material for the removal of hazardous elements from wastewater and landfill gases, as soil replacement in agricultural activities, as partial or complete substitute of raw materials for the manufacture of ceramic-based products, as landfill cover and as biogas production enhancer, were gathered, collated and analysed. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. Advanced study of transport analysis in bentonite (2)

    International Nuclear Information System (INIS)

    Kawamura, Katsuyuki

    2004-03-01

    Solute and radionuclide transport analysis in buffer material made of bentonite clay is essential in safety assessment of a geological disposal facility for high-level radioactive waste (HLW). It is keenly required to understand the true physical and chemical process of the transport phenomena and to improve reliability of the safety assessment, since any conventional methods based on experimental models involve difficulty to estimate the robustness for a very long-term behavior. In order to solve this difficulty we start with the molecular dynamics (MD) simulation method for understanding the molecular-based fundamental properties such as an ionic state and diffusion characteristics of hydrated smectite clay minerals, and we extend the microscale properties to the macroscale behaviors by applying the multiscale homogenization method. In the study of this year we improved the MD atomic model for the hydrated clay minerals, and a new adsorption-diffusion analysis scheme by the homogenization analysis (HA). In the MD simulation first we improved the interatomic potential model for the smectitic clays. Then the behaviors of hydrated Na-beidellite and its substitution products by Cs and Ca were calculated. Not only the swelling behaviors of the beidellite minerals but also the diffusion characteristics of cations in the interlayer space are calculated. A microscopic image is important to specify micro/macro behavior of bentonite. Last year we observed microstructures of bentonite by using a confocal laser scanning microscope (LSM). Based on the knowledge of the local material properties obtained by MD and the microscopic observation we simulated the micro-/macro-behavior of diffusion experiments of the bentonite which included the microscale adsorption characteristics at the edges of clay minerals. (author)

  5. Advanced study of transport analysis in bentonite (3)

    International Nuclear Information System (INIS)

    Kawamura, Katsuyuki

    2005-02-01

    Solute and radionuclide transport analysis in buffer material made of bentonite clay is essential in safety assessment of a geological disposal facility for high-level radioactive waste (HLW). It is keenly required to understand the true physical and chemical process of the transport phenomena and to improve reliability of the safety assessment, since any conventional methods based on experimental models involve difficulty to estimate the robustness for a very long-term behavior. In order to solve this difficulty we start with the molecular dynamics (MD) simulation method for understanding the molecular-based fundamental properties such as an ionic state and diffusion characteristics of hydrated smectite clay minerals, and we extend the microscale properties to the macroscale behaviors by applying the multiscale homogenization analysis (HA) method. In the study of this year we improved the MD atomic model for the hydrated clay minerals, and a new adsorption-diffusion analysis scheme by the homogenization analysis (HA). In the MD simulation we precisely simulated the molecular behaviors of cations and H 2 O in the neighborhood of a clay mineral. In FY2002 the swelling property and diffusivity of interlayer cations, Cs and Ca, were calculated. In FY2003 the interatomic potential model was improved, and the diffusivity of several interlayer cations were calculated. In FY2004 the interatomic potential model was further improved, and the swelling and diffusive properties became more realistic. Then the coordination number of cations were calculated. A microscopic image is important to specify micro/macro behavior of bentonite. In FY2002 we observed microstructures of bentonite by using a confocal laser scanning microscope (LSM). In FY2003 based on the knowledge of the local material properties obtained by MD and the microscopic observation we simulated the micro-/macro-behavior of diffusion experiments of the bentonite which included the microscale adsorption

  6. Diffusion of uranium in the bentonite in the presence of carbon steel

    International Nuclear Information System (INIS)

    Idemitsu, Kazuya

    1994-01-01

    The most largely expected method for disposal method of high level radioactive waste liquid forming in reprocessing process of used nuclear fuel is a method of geological disposal into ground layer stable hydrologically and geologically and of some hundreds meter under ground on a shape of glass solid excellent to chemical durability (deep ground disposal). Storing container for the ground disposal is surrounded by a kind of buffer material used for barrier. For the buffer candidate material, there are some swelling clay minerals such as bentonite and so forth. In this study, some experiments on diffusion behavior of uranium under reductive environment coexisting bentonite with corroded overpack material were conducted. At the same time, experiments under oxidative environment were also conducted to compare with both results, and effect of quartz sand mixing and buffer material density change on diffusion behavior was investigated. As a result, it was found that uranium diffusion coefficient in saturated swelled bentonite buffer and bentonite/quartz mixing buffer was (0.90-1.4)x10 -12 under oxidative condition, and (3.5-11)x10 -14 under reductive condition, that absorption of uranium to bentonite is mainly due to montmorillonite, and so forth. (G.K.)

  7. Assessment Criteria of Bentonite Binding Properties

    Directory of Open Access Journals (Sweden)

    S. Żymankowska-Kumon

    2012-09-01

    Full Text Available The criteria, with which one should be guided at the assessment of the binding properties of bentonites used for moulding sands, areproposed in the paper. Apart from the standard parameter which is the active bentonite content, the unrestrained growth indicator should be taken into account since it seems to be more adequate in the estimation of the sand compression strength. The investigations performed for three kinds of bentonites, applied in the Polish foundry plants, subjected to a high temperature influences indicate, that the pathway of changes of the unrestrained growth indicator is very similar to the pathway of changes of the sand compression strength. Instead, the character of changes of the montmorillonite content in the sand in dependence of the temperature is quite different. The sand exhibits the significant active bentonite content, and the sand compression strength decreases rapidly. The montmorillonite content in bentonite samples was determined by the modern copper complex method of triethylenetetraamine (Cu(II-TET. Tests were performed for bentonites and for sands with those bentonites subjected to high temperatures influences in a range: 100-700ºC.

  8. Modeling of Coupled Thermo-Hydro-Mechanical-Chemical Processes for Bentonite in a Clay-rock Repository for Heat-generating Nuclear Waste

    Science.gov (United States)

    Xu, H.; Rutqvist, J.; Zheng, L.; Birkholzer, J. T.

    2016-12-01

    Engineered Barrier Systems (EBS) that include a bentonite-based buffer are designed to isolate the high-level radioactive waste emplaced in tunnels in deep geological formations. The heat emanated from the waste can drive the moisture flow transport and induce strongly coupled Thermal (T), Hydrological (H), Mechanical (M) and Chemical (C) processes within the bentonite buffer and may also impact the evolution of the excavation disturbed zone and the sealing between the buffer and walls of an emplacement tunnel The flow and contaminant transport potential along the disturbed zone can be minimized by backfilling the tunnels with bentonite, if it provides enough swelling stress when hydrated by the host rock. The swelling capability of clay minerals within the bentonite is important for sealing gaps between bentonite block, and between the EBS and the surrounding host rock. However, a high temperature could result in chemical alteration of bentonite-based buffer and backfill materials through illitization, which may compromise the function of these EBS components by reducing their plasticity and capability to swell under wetting. Therefore, an adequate THMC coupling scheme is required to understand and to predict the changes of bentonite for identifying whether EBS bentonite can sustain higher temperatures. More comprehensive links between chemistry and mechanics, taking advantage of the framework provided by a dual-structure model, named Barcelona Expansive Model (BExM), was implemented in TOUGHREACT-FLAC3D and is used to simulate the response of EBS bentonite in in clay formation for a generic case. The current work is to evaluate the chemical changes in EBS bentonite and the effects on the bentonite swelling stress under high temperature. This work sheds light on the interaction between THMC processes, evaluates the potential deterioration of EBS bentonite and supports the decision making in the design of a nuclear waste repository in light of the maximum allowance

  9. Development and validation of mechanical model for saturated/unsaturated bentonite buffer

    International Nuclear Information System (INIS)

    Yamamoto, S.; Komine, H.; Kato, S.

    2010-01-01

    Document available in extended abstract form only. Development and validation of mechanical models for bentonite buffer and backfill materials are one of important subjects to appropriately evaluate long term behaviour or condition of the EBS in radioactive waste disposal. The Barcelona Basic Model (BBM), which is one of extensions of the modified Cam-Clay model for unsaturated and expansive soil, has been developed and widely applied to several problems by using the coupled THM code, Code B right. Advantage of the model is that mechanical characteristics of buffer and backfill materials under not only saturated condition but also unsaturated one are taken account as well as swelling characteristics due to wetting. In this study the BBM is compared with already existing experimental data and already developed another model in terms of swelling characteristics of Japanese bentonite Kunigel-V1, and is validated in terms of consolidation characteristics based on newly performed controlled-suction oedometer tests for the Kunigel-V1 bentonite. Komine et al. (2003) have proposed a model (set of equations) for predicting swelling characteristics based on the diffuse double layer concept and the van der Waals force concept etc. They performed a lot of swelling deformation tests of bentonite and sand-bentonite mixture to confirm the applicability of the model. The BBM well agrees with the model proposed by Komine et al. and the experimental data in terms of swelling characteristics. Compression index and swelling index depending on suction are introduced in the BBM. Controlled-suction consolidation tests (oedometer tests) were performed to confirm the applicability of the suction dependent indexes to unsaturated bentonite. Compacted bentonite with initial dry density of 1.0 Mg/m 3 was tested. Constant suction, 80 kPa, 280 kPa and 480 kPa was applied and kept during the consolidation tests. Applicability of the BBM to consolidation and swelling behaviour of saturated and

  10. Activation of wine bentonite with gamma rays

    International Nuclear Information System (INIS)

    Goranov, N.; Antonov, M.

    1997-01-01

    The action of gamma rays on wine bentonite as well as influence of its adsorption and technologic qualities on the composition and stability of wines against protein darkening and precipitation has been studied. The experiments were carried out with wine bentonite produced in the firm Bentonite and irradiated with doses of 0.4, 0.6, 0.8 and 1.0 MR. White and red wines have been treated with irradiated bentonite under laboratory conditions at 1.0 g/dm 3 . All samples are treated at the same conditions. The flocculation rate of the sediment was determined visually. Samples have been taken 24 h later from the cleared wine layers. The following parameters have been determined: clarification, filtration rate, phenolic compounds, calcium, colour intensity, total extracted substances, etc. The volume of the sediment has been determined also. The control samples have been taken from the same unirradiated wines. The results showed better and faster clarification in on the third, the 20th and the 24th hours with using of gamma-irradiated at doses 0.8 and 1.0 MR. The sediment was the most compact and its volume - the smallest compared to the samples treated with bentonite irradiated with doses of 0.6 and 0.4 MR. This ensures a faster clarification and better filtration of treated wines. The bentonite activated with doses of 0.8 and 1.0 MR adsorbs the phenolic compounds and the complex protein-phenolic molecules better. In the same time it adsorbs less extracted substances compared to untreated bentonite and so preserves all organoleptic properties of wine. The irradiated bentonite adsorbs less the monomers of anthocyan compounds which ensures brighter natural colour of wine. The gamma-rays activation consolidates calcium in the crystal lattice of bentonite particles and in this way eliminates the formation of crystal precipitates

  11. NMR Measurements of Granular Flow and Compaction

    Science.gov (United States)

    Fukushima, Eiichi

    1998-03-01

    Nuclear magnetic resonance (NMR) can be used to measure statistical distributions of granular flow velocity and fluctuations of velocity, as well as spatial distributions of particulate concentration, flow velocity, its fluctuations, and other parameters that may be derived from these. All measurements have been of protons in liquid-containing particles such as mustard seeds or pharmaceutical pills. Our favorite geometry has been the slowly rotating partially filled rotating drum with granular flow taking place along the free surface of the particles. All the above-mentioned parameters have been studied as well as a spatial distribution of particulate diffusion coefficients, energy dissipation due to collisions, as well as segregation of non-uniform mixtures of granular material. Finally, we describe some motions of granular material under periodic vibrations.

  12. Photodegradation of Methylene Blue by TiO2-Fe3O4-Bentonite Magnetic Nanocomposite

    Directory of Open Access Journals (Sweden)

    Wei Chen

    2015-01-01

    Full Text Available Fe3O4-bentonite nanoparticles have been prepared by a coprecipitation technique under a nitrogen atmosphere. An aqueous suspension of bentonite was first modified with FeCl2 and FeCl3. TiO2 was then loaded onto the surface of the Fe3O4-bentonite by a sol-gel method. After sufficient drying, the colloidal solution was placed in a muffle furnace at 773 K to obtain the TiO2-Fe3O4-bentonite composite. The material has been characterized by scanning electron microscopy (SEM, X-ray diffraction (XRD analysis, and vibrating sample magnetometry (VSM. Morphological observation showed that Fe3O4 and TiO2 nanoparticles had been adsorbed on the surface of bentonite nanoneedles. The material was then applied for the photodegradation of the azo dye methylene blue (MB. It was found that the removal efficiency of MB exceeded 90% under UV illumination, and that only a 20% mass loss was incurred after six cycles. The composite material thus showed good photocatalytic performance and recycling properties.

  13. Mechanisms and models for bentonite erosion

    International Nuclear Information System (INIS)

    Neretnieks, Ivars; Longcheng Liu; Moreno, Luis

    2009-12-01

    There are concerns that the bentonite buffer surrounding the canisters with spent nuclear fuel may erode when non-saline groundwaters seep past the buffer. This is known to happen if the water content of ions is below the critical coagulation concentration CCC. Above the CCC the smectite forms a coherent gel, which does not release particles. One main effort in this study has been directed to assess under which conditions the pore water composition of the gel at the gel/water interface could be lower than the CCC. Another main effort has been directed to understanding the behaviour of expansive gel when the pore water is below the CCC. We have developed a Dynamic model for sodium gel expansion in fractures where the gel soaks up non-saline water as it expands. The model is based on a force balance between and on smectite particles, which move in the water. The Dynamic model of gel expansion showing the evolution in time and space of a gel was successfully tested against expansion experiments in test tubes. The expansion was measured with high resolution and in great detail over many months by Magnetic Resonance Imaging. The model also predicted the gel expansion through filters with very narrow pores well. A gel viscosity model of dilute gels was derived, which accounts for ion concentration influence as well as the volume fraction of smectite in the gel. The model accounts for the presence of the DDL, which seemingly makes the particles larger so that they interact at lower particle densities. Simulations were performed for a case where the gel expands outward into the fracture that intersects the deposition hole. Fresh groundwater approaches and passes the gel/water interface. Smectite colloids move out into the water due to the repulsive forces between the particle and by Brownian motion (effect included in the Dynamic model). The dilute gel/sol is mobilised and flows downstream in a thin region where the viscosity is low enough to permit flow. Sodium diffuses

  14. Diffusion, sorption, and retardation processes of anions in bentonite and organo-bentonites for multibarrier systems

    Science.gov (United States)

    Schampera, Birgit; Dultz, Stefan

    2013-04-01

    The low permeability, high cation exchange capacity (CEC) and plasticity of bentonites favor their use in multibarrier systems of waste deposits [1]. Bentonites have a high CEC but their ability to sorb anions is very low. There is, however, need for retardation of anions and organic pollutants in many applications. Bentonites, modified with certain organic cations, have the capacity to sorb anions and non-polar organic compounds in addition to cations. Investigations on organically modified clays address a wide variety of applications including immobilization of pollutants in contaminated soils, waste water treatment and in situ placement for the protection of ground water [2]. Many experiments on anion and cation sorption of organo-clays were conducted in the batch mode which does not reflect solid-liquid ratios and material densities in barrier systems. Diffusion experiments on compacted clays allow the evaluation of transport processes and sorption of pollutants at conditions relevant for repositories. For organo-clays only few diffusion studies are published e.g. [3] measured the diffusion of tritium and [4] the diffusion of H2O in bentonite and organo-bentonites. The organic cation hexadecylpyridinium (HDPy) was added to Wyoming bentonite (MX-80) in amounts corresponding to 2-400 % of the CEC. The uptake of organic cations was determined by the C-content, XRD and IR-spectroscopy. Wettability was analyzed by the contact angle. Physical, chemical and mineralogical properties of clays were characterized. Diffusion experiments were carried out in situ in a cell attached to the ATR-unit of a FTIR-spectrometer. For H2O-diffusion the compacted organo-clays are saturated first with D2O, afterwards H2O is supplied to the surface at the top of the clay platelet. Anion-diffusion was conducted with NO3--solution instead of H2O only having characteristic IR band positions at 1350 cm-1. Three different concentrations (0.25M, 0.5M and 1M) were used. Additional batch

  15. Early age sealing of buffer-rock gap by artificial wetting to induce bentonite swelling

    International Nuclear Information System (INIS)

    Holt, Erika; Marjavaara, Pieti

    2012-01-01

    Document available in extended abstract form only. The aim of this work is to study the homogeneous and rapid swelling of bentonite in the gap between the buffer blocks and the rock wall of the Olkiluoto disposal facility by artificial wetting. The focus was on the construction period of the deposition hole and buffer, and thus only the very early ages of the first weeks. In practice it is desirable that the bentonite material has a volume increase sufficient enough to prevent rock scaling while lowering the risks of bentonite piping and erosion due to potential water flow. This initial study was done in a small-scale mock-up in laboratory conditions. The small-scale steel mock-up had dimensions of 39 cm in height by 36 cm in diameter and included 12 pressure sensors, two displacement transducers, thermal couples, and pore water pressure measurements. The radial and axial pressure development was typically measured over a two week period to assess the rate and magnitude of sealing. A steel confining lid was used for simulating overpressure, though in some cases a plexiglass lid was used to take video images of the gap sealing. The buffer blocks were produced by isostatic compression of 100 MPa. The material was MX-80 Wyoming bentonite having a water content of approximately 13% and a dry density of 1890 kg/m 3 . The testing samples were dry sawn and core drilled from the large block and machined to their final dimensions. These were typically 30 x 30 cm, either as a solid block or three disks of 10 cm height each. The diameter was sometimes varied to allow for a change of gap width between 25 to 50 mm The study included various scenarios, such as: eccentric aligned blocks with gap sizes of 5 and 45 mm, free upward swelling or confinement, different types of pellet and granular gap filling, addition of water at varying rates, and longer term test duration. The samples were typically disassembled after two weeks. At this ending point, material assessments were done

  16. Development of high-density bentonite barriers by means of spraying methods. Part 2. Investigation of field conditions

    International Nuclear Information System (INIS)

    Tanaka, Toshiyuki; Kobayashi, Ichizo; Nakajima, Makoto; Toida, Masaru

    2006-01-01

    The authors have developed a method of constructing high-density bentonite by means of wet spraying to act as a backfill material in narrow places in radioactive waste disposal facilities. On the basis of the results of laboratory tests, they conducted field spraying tests to investigate the field conditions. The results of these tests are summarized as follows: 1) The bentonite could be sprayed smoothly by using a rotary spraying machine and a screw conveyor. 2) Provided that the air flow was at least 18.5 m 3 /min and the nozzle diameter did not exceed 25 mm, an average dry density of bentonite of 1.6 Mg/m 3 or higher could be achieved. 3) The dry density was constant within the spraying distance range 500 mm ∼ 2000 mm. 4) With a nozzle diameter of 19 mm, a spraying distance of 1000 mm, and a water content of 19.5%, an average dry density of the sprayed bentonite of 1.6 Mg/m 3 or higher and a rebound ratio not exceeding 30% was achieved. 5) The dry density of the sprayed bentonite decreased as the volume of bentonite supplied was increased, and it was shows to be closely related to the rotational speed of the spraying machine and the volume of bentonite sprayed from each hole. (author)

  17. Adsorption of strontium ions on bentonites of slovak provenance - Influence of pH change of medium

    International Nuclear Information System (INIS)

    Galambos, M.; Kufcakova, J.; Rajec, P.; Paucova, V.

    2007-01-01

    Bentonite is a natural clay and one of the most promising candidates for use as a buffer material in the geological disposal systems for spent fuel and high-level nuclear waste. It is intended to isolate metal canisters with highly radioactive waste products from the surrounding rocks because of its ability to retard the movement of radionuclides by sorption. Slovak republic disposes of many significant deposits of bentonites, e.g. Jelsovy potok, Kopernica, Lieskovec, Lastovce, etc. The bentonites present significant group of natural nanomaterials composed of microcrystallic particles of montmorillonite. Bentonite is characterized by a low hydraulic conductivity, low throughput and excellent sorption capacity for cationic fission products of 235 U (e.g. 89 Sr, 90 Sr, 137 Cs). Sorption of strontium on bentonite from various Slovak deposits was studied using batch technique. Distribution coefficients (K d ) were determined for bentonite-strontium solution system as a function of contact time, pH, sorbent and sorbate concentration. The data were interpreted in term of Langmuir isotherm. The uptake of Sr was rapid and equilibrium was reached almost instantaneously. The effect of pH, on the sorption of metal ions on bentonite was studied by varying the pH of the aqueous metal solutions. The sorption of this nuclide increased by increasing pH. The percentage sorption decreased with increasing metal concentrations. These results could be helpful for nuclear waste management, for waste water effluents containing low concentrations of strontium. (authors)

  18. Mechanisms and models for bentonite erosion

    Energy Technology Data Exchange (ETDEWEB)

    Neretnieks, Ivars; Longcheng Liu; Moreno, Luis (Dept. of Chemical Engineering and Technology, School of Chemical Science and Engineering, Royal Inst. of Technology, KTH, Stockholm (Sweden))

    2009-12-15

    There are concerns that the bentonite buffer surrounding the canisters with spent nuclear fuel may erode when non-saline groundwaters seep past the buffer. This is known to happen if the water content of ions is below the critical coagulation concentration CCC. Above the CCC the smectite forms a coherent gel, which does not release particles. One main effort in this study has been directed to assess under which conditions the pore water composition of the gel at the gel/water interface could be lower than the CCC. Another main effort has been directed to understanding the behaviour of expansive gel when the pore water is below the CCC. We have developed a Dynamic model for sodium gel expansion in fractures where the gel soaks up non-saline water as it expands. The model is based on a force balance between and on smectite particles, which move in the water. The Dynamic model of gel expansion showing the evolution in time and space of a gel was successfully tested against expansion experiments in test tubes. The expansion was measured with high resolution and in great detail over many months by Magnetic Resonance Imaging. The model also predicted the gel expansion through filters with very narrow pores well. A gel viscosity model of dilute gels was derived, which accounts for ion concentration influence as well as the volume fraction of smectite in the gel. The model accounts for the presence of the DDL, which seemingly makes the particles larger so that they interact at lower particle densities. Simulations were performed for a case where the gel expands outward into the fracture that intersects the deposition hole. Fresh groundwater approaches and passes the gel/water interface. Smectite colloids move out into the water due to the repulsive forces between the particle and by Brownian motion (effect included in the Dynamic model). The dilute gel/sol is mobilised and flows downstream in a thin region where the viscosity is low enough to permit flow. Sodium diffuses

  19. Organophilization and characterization of commercial bentonite clays

    International Nuclear Information System (INIS)

    Cunha, B.B. da; Lima, J.C.C.; Alves, A.M.; Araujo, E.M.; Melo, T.J.A. de

    2012-01-01

    Bentonite clay is a plastic changes resulting from volcanic ash, consisting mostly of montmorillonite. The state of Paraiba is a major source of bentonite clay from Brazil, where the main oil fields are located in Boa Vista and represents the largest national production of raw and beneficiated bentonite. Aimed at the commercial value of this type of clay and its high applicability in the polls, this article aims to make a comparison between two kinds of clay, a national (Brasgel) and other imported (Cloisite) from organophilization of two commercial bentonite, ionic surfactant with Praepagem WB, and characterize them by XRD, FTIR and TG / DTG. We observe that despite getting inferior properties, the clay presents national values very similar to those presented by imported clay. (author)

  20. Thermal properties of bentonite under extreme conditions

    Energy Technology Data Exchange (ETDEWEB)

    Vasicek, R. [Czech Technical Univ., Centre of Experimental Geotechnics, Faculty of Civil Engineering, Prague (Czech Republic)

    2005-07-01

    Centre of Experimental Geotechnics (CEG) deals with the research of the behaviour of bentonite and clays. The measurement of thermal properties is not so frequent test in geotechnical laboratory but in relation to deep repository it is a part which should not be overlooked. The reason is the heat generated by canister with spent nuclear fuel and possible influence of the heat on the materials of the engineered barrier. In the initial stages following the burial of canister with the waste the barrier materials will be exposed to elevated temperature. According to existing information, these temperatures should not exceed 90 C. That heat can induce a creation of cracks and opening of joint between highly compacted blocks. It will predispose the bentonite barrier to penetration of water from surrounding towards to canister. Therefore easy removal of heat through the barrier is required. It is essential that the tests aimed at determining the real values of measured parameters are carried out in conditions identical with those anticipated in a future disposal system. These relatively complicated thermophysical tests are logical continuation of the simple ones, carried out under laboratory temperature and on not fully saturated samples without possibility to measure the swelling pressure. Thermophysical properties and swelling pressure are dominantly influenced by water content (which is influenced by temperature). Therefore is important to realize the tests under different moisture and thermal conditions. These tests are running at the APT-PO1 Analyser, designed to fulfill mentioned requirements - it allows measurement of thermal properties under temperature up to 200 C and swelling pressure up to 20 MPa. The device is capable to register the evolution of temperature, swelling and vapor pressure. The measurement of thermal conductivity and volume heat capacity is realized by the dynamic impulse method with point source of heat. Four types of tests are possible: at

  1. Advances on study of temperature effects on hydro-mechanical behaviour of densely compacted bentonite

    International Nuclear Information System (INIS)

    Ye Weimin; Wan Min; Chen Bao; Liu Yuemiao; Cui Yujun

    2008-01-01

    During the operation of a multiple-barrier geological repository, bentonite that works as a buffer/fill material of an artificial barrier will suffer complex coupling effects of thermal (T), hydrological (H), mechanical (M) process, which comes from heat of the nuclear waste radiation, mechanical stress from parent rock mass and seepage action of groundwater. The scientific results show that temperature has influence on the water retention, saturated permeability, swelling pressure, swelling strain and thermal strain of compacted bentonite. As a whole, the research about GMZ (Gao Miaozi) bentonite, which may potentially be chose as Chinese buffer/backfill material for high radioactive nuclear waste disposal, has a long way to go compare to developed contraries. Based on comprehensive laboratory tests and advanced theoretical framework, both of the study on behaviour of compacted GMZ bentonite under HTM coupling conditions, and the establishment of a constitutive relation for prediction of behaviour of compacted bentonite under multi-field coupling conditions are important in theoretic and practical way. (authors)

  2. Study of waterproof capabilities of the engineered barrier containing bentonite in near surface radioactive waste repositories

    International Nuclear Information System (INIS)

    Luu Cao Nguyen; Nguyen Ba Tien; Doan Thi Thu Hien; Nguyen Van Chinh; Vuong Huu Anh

    2017-01-01

    In Vietnam, the study of nuclear fuel cycle is in first steps, such as the exploitation and uranium processing. These processes generated large amounts of radioactive waste over-timing. The naturally occurring radioactive material and technologically enhanced radioactive material (NORM/TENORM) waste, which would be large, needs to be managed and disposed reasonably by effective methods. These wastes were used to be disposal in the near surface. It was therefore very important to study the model of radioactive waste repository, where bentonite waterproofing layer would be applied for the engineered barrier. The aim of this study was to obtain the preliminary parameters for low-level radioactive waste disposal site being suitable with the conditions of Vietnam. The investigation of the ratio between soil and bentonite was taken part. The experiments with some layers of waterproofing material with the ratio of soil and bentonite as 75/25, 50/50 and 25/75 were carried out to test the moving of uranium nuclide through these waterproofing material layers. Analyzing the uranium content in each layer (0.1 cm) of pressed soil - bentonite mixture (as a block) to determine the uranium nuclide adsorption from solution into the materials in the different ratios at the different times: 1, 2 and 3 months was carried out. The results showed that the calculated average rate of uranium nuclide migration into the soil - bentonite layer was 5.4x10 -10 , 5.4x10 -10 and 3.85x10 -10 m/s corresponding to the waterproofing layer thickness (for 300 years) 4.86 m, 4.86 m and 3.63 m respectively, which was due on the ratio of soil and bentonite 75/25, 50/50, 25/75 to keep the safety for the repository. (author)

  3. Calculation of saturated hydraulic conductivity of bentonite

    International Nuclear Information System (INIS)

    He Jun

    2006-01-01

    Hydraulic conductivity test has some defects such as weak repeatability, time-consuming. Taking bentonite as dual porous media, the calculation formula of the distance, d 2 , between montmorillonite in intraparticle pores is deduced. Improved calculated method of hydraulic conductivity is obtained using d 2 and Poiseuille law. The method is valid through the comparison with results of test and other methods. The method is very convenient to calculate hydraulic conductivity of bentonite of certain montmorillonite content and void ratio. (authors)

  4. Water retention behaviour of compacted bentonites: experimental observations and constitutive model

    Directory of Open Access Journals (Sweden)

    Dieudonne Anne-Catherine

    2016-01-01

    Full Text Available Bentonite-based materials are studied as potential barriers for the geological disposal of radioactive waste. In this context, the hydro-mechanical behaviour of the engineered barrier is first characterized by free swelling conditions followed by constant volume conditions. This paper presents an experimental study conducted in order to characterize the water retention behaviour of a compacted MX-80 bentonite/sand mixture. Then, based on observations of the material double structure and the water retention mechanisms in compacted bentonites, a new water retention model is proposed. The model considers adsorbed water in the microstructure and capillary water in the aggregate-porosity. The model is calibrated and validated against the experimental data. It is used for better understanding competing effects between volume change and water uptake observed during hydration under free swelling conditions.

  5. Influence of natural or organophilic bentonite for flammable of the poly(ethylene-co-vinyl acetate)

    International Nuclear Information System (INIS)

    Heyder, Eduardo T.; Kloss, Juliana R.; Morita, Reinaldo Y.; Barbosa, Ronilson V.

    2015-01-01

    The manufacture polymeric applied in electrical sector in general use additives which act as flame retardants, for example, some borates, phosphates, and halogenated hydroxides. An alternative material for this purpose frequently reported in the literature because the flame resistance or flame retardancy is organoclay. Thus, the objective of this study is to evaluate the flammability of mixtures of EVA/natural bentonite and EVA/organoclay containing modifier as a species free of quaternary ammonium ions. The natural bentonite and organoclay were characterized by X-ray diffraction and scanning electron microscopy and materials were evaluated by X-ray diffraction and the flammability test. Regarding the combustion rate values, there was a reduction of flame propagation in EVA/natural bentonite (3.0%), showing that in this case the clay without modifier acted as a physical barrier and promoted retardant action of flame. (author)

  6. Tests for the characterization of bentonite used in the manufacture of clay geo synthetic barriers (GBR-C)

    International Nuclear Information System (INIS)

    Leiro, A.; Mateo, B.; Garcia, H.; Llorente, S.

    2011-01-01

    Bentonites are clays essentially composed of the smectite minerals. they are used in the manufacture of Clay Geosynthetic Barriers )GBR-C) which are low-permeability geosynthetic materials, forming part of the lining technologies and construction waterproofing systems. This article shows a series of testing to evaluate the quality of the bentonite for such use. Correlation between different testing has also been established in order to identify the most suitable ones for their characterization. (Author) 8 refs.

  7. Hydraulic conductivity of some bentonites in artificial seawater

    International Nuclear Information System (INIS)

    Komine, Hideo; Murakami, Satoshi; Yasuhara, Kazuya

    2011-01-01

    A high-level radioactive waste disposal facility might be built in a coastal area in Japan from the viewpoint of feasible transportation of waste. Therefore, it is important to investigate the effects of seawater on a bentonite-based buffer. This study investigated the influence of seawater on hydraulic conductivity of three common sodium-types of bentonite and one calcium-type bentonite by the laboratory experiments. >From the results of laboratory experiment, this study discussed the influence of seawater on hydraulic conductivity of bentonites from the viewpoints of kinds of bentonite such as exchangeable-cation type and montmorillonite content and dry density of bentonite-based buffer. (author)

  8. Rapid increases in permeability and porosity of bentonite-sand mixtures due to alteration by water vapor

    International Nuclear Information System (INIS)

    Couture, R.A.

    1984-01-01

    Packed columns of canister packing material containing 25% bentonite and 75% quartz or basalt sand, were exposed to water vapor at temperatures up t 260 0 C. The permeabilities of the columns were subsequently measured after complete saturation with liquid water in a pressurized system. Exposure to water vapor caused irreversible increases in permeability by factors of up to 10 5 . After saturation with liquid water, the permeability was nearly independent of temperature. The increases in permeability were due to a large decrease in the ability of the bentonite to swell in water. Calculations suggest that swelling of bentonite altered at 250 0 C was not sufficient to fill the pore spaces. If the pore spaces are filled, the mixture will form an effective barrier against flow, diffusion, and transport of colloids. The results suggest that if bentonite-based canister packing material is exposed even briefly to water vapor at high temperatures in a high-level nuclear waste repository, its performance will be seriously impaired. The problem is less severe if the proportion of bentonite is high and the material is highly compacted. Previous results show significant degradation of bentonite by water vapor at temperatures as low as 150 0 C. This suggests that in some repositories, backfill in tunnels and drifts may also be affected. 9 references, 5 figures, 1 table

  9. A constitutive law for dense granular flows.

    Science.gov (United States)

    Jop, Pierre; Forterre, Yoël; Pouliquen, Olivier

    2006-06-08

    A continuum description of granular flows would be of considerable help in predicting natural geophysical hazards or in designing industrial processes. However, the constitutive equations for dry granular flows, which govern how the material moves under shear, are still a matter of debate. One difficulty is that grains can behave like a solid (in a sand pile), a liquid (when poured from a silo) or a gas (when strongly agitated). For the two extreme regimes, constitutive equations have been proposed based on kinetic theory for collisional rapid flows, and soil mechanics for slow plastic flows. However, the intermediate dense regime, where the granular material flows like a liquid, still lacks a unified view and has motivated many studies over the past decade. The main characteristics of granular liquids are: a yield criterion (a critical shear stress below which flow is not possible) and a complex dependence on shear rate when flowing. In this sense, granular matter shares similarities with classical visco-plastic fluids such as Bingham fluids. Here we propose a new constitutive relation for dense granular flows, inspired by this analogy and recent numerical and experimental work. We then test our three-dimensional (3D) model through experiments on granular flows on a pile between rough sidewalls, in which a complex 3D flow pattern develops. We show that, without any fitting parameter, the model gives quantitative predictions for the flow shape and velocity profiles. Our results support the idea that a simple visco-plastic approach can quantitatively capture granular flow properties, and could serve as a basic tool for modelling more complex flows in geophysical or industrial applications.

  10. Investigation on compression behaviour of highly compacted GMZ01 bentonite with suction and temperature control

    Energy Technology Data Exchange (ETDEWEB)

    Ye, W.M., E-mail: ye_tju@tongji.edu.cn [Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Tongji University, Shanghai 200092 (China); United Research Center for Urban Environment and Sustainable Development, The Ministry of Education, Shanghai 200092 (China); Zhang, Y.W.; Chen, B.; Zheng, Z.J.; Chen, Y.G. [Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Tongji University, Shanghai 200092 (China); Cui, Y.J. [Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Tongji University, Shanghai 200092 (China); Ecole des Ponts ParisTech, UR Navier/CERMES 77455 (France)

    2012-11-15

    Highlights: Black-Right-Pointing-Pointer Heating induced volumetric change of GMZ01 bentonite depends on suction. Black-Right-Pointing-Pointer Suction has significant influence on compressibility. Black-Right-Pointing-Pointer Temperature has slight influence on compressibility. - Abstract: In this paper, an oedometer with suction and temperature control was developed. Mechanical compaction tests have been performed on the highly compacted GMZ01 bentonite, which has been recognized as potential buffer/backfill material for construction of Chinese high-level radioactive waste (HLW) geological repository, under conditions of suction ranging from 0 to 110 MPa, temperature from 20 to 80 Degree-Sign C and vertical pressure from 0.1 to 80 MPa. Based on the test results, suction and temperature effects on compressibility parameters are investigated. Results reveal that: (1) at high suctions, heating induced an expansion, while contraction is induced by heating at low suctions. The thermal expansion coefficient of GMZ01 bentonite measured is 1 Multiplication-Sign 10{sup -4} Degree-Sign C{sup -1}; (2) with increasing suction, the elastic compressibility {kappa} and the plastic compressibility {lambda}(s) of the highly compacted GMZ01 bentonite decrease, while the pre-consolidation pressure increases markedly; (3) with increasing temperature, the elastic compressibility of compacted GMZ01 bentonite changes insignificantly, while the plastic compressibility {lambda}(s) slightly decreases and the yield surface tends to shrink.

  11. Investigation on compression behaviour of highly compacted GMZ01 bentonite with suction and temperature control

    International Nuclear Information System (INIS)

    Ye, W.M.; Zhang, Y.W.; Chen, B.; Zheng, Z.J.; Chen, Y.G.; Cui, Y.J.

    2012-01-01

    Highlights: ► Heating induced volumetric change of GMZ01 bentonite depends on suction. ► Suction has significant influence on compressibility. ► Temperature has slight influence on compressibility. - Abstract: In this paper, an oedometer with suction and temperature control was developed. Mechanical compaction tests have been performed on the highly compacted GMZ01 bentonite, which has been recognized as potential buffer/backfill material for construction of Chinese high-level radioactive waste (HLW) geological repository, under conditions of suction ranging from 0 to 110 MPa, temperature from 20 to 80 °C and vertical pressure from 0.1 to 80 MPa. Based on the test results, suction and temperature effects on compressibility parameters are investigated. Results reveal that: (1) at high suctions, heating induced an expansion, while contraction is induced by heating at low suctions. The thermal expansion coefficient of GMZ01 bentonite measured is 1 × 10 −4 °C −1 ; (2) with increasing suction, the elastic compressibility κ and the plastic compressibility λ(s) of the highly compacted GMZ01 bentonite decrease, while the pre-consolidation pressure increases markedly; (3) with increasing temperature, the elastic compressibility of compacted GMZ01 bentonite changes insignificantly, while the plastic compressibility λ(s) slightly decreases and the yield surface tends to shrink.

  12. Improving the quality of biopolymer (poly lactic acid) with the addition of bentonite as filler

    Science.gov (United States)

    Suryani; Agusnar, Harry; Wirjosentono, Basuki; Rihayat, Teuku; Nurhanifa

    2017-07-01

    PLA (Poly Lactid Acid) - Bentonite polymer nanocomposite which is a combination of natural and nanometer-scale inorganic substances created through three processes, mixing using a melt blending, molding with a hot press using specimens Standard ASTM D 638 Type IV and drying. In this study, PLA combined with two types of natural bentonite obtained from different areas to find differences in the quality of the results of characterization. To optimize the performance of filler, before mixing, bentonite have to furificate first with (NaPO3)6 and also open the interlayer space with CTAB. D-spacing of bentonite imterlayer were analyze by X-Ray difraction (XRD). Characterization bionanocomposite resulting morphologic structure was tested using a Transmission Electron Microscope (TEM). Mechanical analysis of PLA-bentonite nanocomposite in the form of tensile strength was tested using a tensile test specimens of standard American Standard for Testing Materials (ASTM) D 638 Type 4, and thermal resistance using Thermo Gravimetric Analysis (TGA).

  13. Removal of heavy metals using bentonite supported nano-zero valent iron particles

    Science.gov (United States)

    Zarime, Nur Aishah; Yaacob, Wan Zuhari Wan; Jamil, Habibah

    2018-04-01

    This study reports the composite nanoscale zero-valent iron (nZVI) which was successfully synthesized using low cost natural clay (bentonite). Bentonite composite nZVI (B-nZVI) was introduced to reduce the agglomeration of nZVI particles, thus will used for heavy metals treatment. The synthesized material was analyzed using physical, mineralogy and morphology analysis such as Brunnaer-Emmett-Teller (BET) surface area, Field Emission Scanning Electron Microscopy (FESEM), X-Ray Diffraction (XRD), Fourier Transform Infrared (FTIR) and X-ray Photoelectron Spectroscopy (XPS). The batch adsorption test of Bentonite and B-nZVI with heavy metals solutions (Pb, Cu, Cd, Co, Ni and Zn) was also conducted to determine their effectiveness in removing heavy metals. Through Batch test, B-nZVI shows the highest adsorption capacity (qe= 50.25 mg/g) compared to bentonite (qe= 27.75 mg/g). This occurred because B-nZVI can reduce aggregation of nZVI, dispersed well in bentonite layers thus it can provide more sites for adsorbing heavy metals.

  14. Simulation of bentonite colloid migration through granite

    International Nuclear Information System (INIS)

    Rosicka, Dana; Hokr, Milan

    2012-01-01

    Document available in extended abstract form only. Full text of publication follows: Colloidal bentonite particles generate at the interface of buffer and host rock in spent nuclear fuel repository due to an erosion process and migrate through granite by the water flow. Stability of these colloids and their migration possibilities have been studied on account of radionuclide transport possibility as colloid could carry adsorbed radionuclides in groundwater through granite. That is why a simulation of bentonite colloid migration in the surrounding of a repository might be requested. According to chemical condition as ionic strength and pH, the colloidal particles coagulate into clusters and that influence the migration of particles. The coagulation kinetics of natural bentonite colloids were experimentally studied in many articles, for example by light scattering techniques. We created a model of coagulation of bentonite colloids and simulation of a chosen experiment with use of the multicomponent reactive transport equation. The coagulation model describes clustering of particles due to attractive van der Waals forces as result of collision of particles due to heat fluctuation and different velocity of particles during sedimentation and velocity gradient of water flow. Next, the model includes influence of repulsive electrostatic forces among colloidal particles leading to stability of particles provided high surface charge of colloids. In the model, each group of clusters is transported as one solution component and the kinetics of coagulation are implemented as reactions between the components: a shift of particles among groups of particles with similar migration properties, according to size of the clusters of colloids. The simulation of migration of bentonite colloid through granite using the coagulation model was calibrated according to experiment results. On the basis of the simulation, one can estimate the basic processes that occur during bentonite colloid

  15. Detection and Analysis of the Magnetic Field Component of Electromagnetic Radiation Emission from Macroscopic Fracturing of Cement-Bound Granular Material

    Science.gov (United States)

    Maquiling, J. T.; Ceralde, P. I. B.

    2016-12-01

    Countries most prone to earthquake damage have been in pursuit of a possible earthquake precursor. This study aims to detect and measure the magnetic field component of the Electromagnetic Radiation (EMR) emitted by quasi-brittle materials that undergo macroscopic fracturing. Cement-Bound Granular Materials (CBGM) were prepared by mixing cement, sand and gravel in a beam mold. Additional aggregates in the form of saw dust were added to produce variable CBGM samples. A concrete beam holder was designed and fabricated such that induced cracks from impact loading would form at the center of the beam. Six Vernier software magnetic field sensors were used to detect the magnetic field (MF) component of the EMR emission. Initial calibration was done to minimize noise in the laboratory. The magnetic field sensors were set at a low amplification range (±6.4x10-3 T) setting with 0.0002 mT precision at 20-50 Hz. Sensor locations and orientations were specified and fixed throughout the experiment. The impact loading process was repeated until concrete failure. The time of drop was determined through the occurrence of peak sound levels (dB) induced by the collision noise using a sound level meter at fast time weighting. Magnetic field fluctuations manifesting near the occurrence of sound level impulses were recorded. Peak magnetic field values within ±200ms from the recorded time of impact were considered to be originating from the concrete fracture. Concrete samples consisting of cement, sand and gravel produced magnetic field emissions measuring 0.58-1.07 μT while the same concrete mixture added with dispersed fine sawdust released 0.55-1.28 μT. A more dispersed set of values of magnetic field emissions were observed for concrete with sawdust. Comparison between the average number of drops done before failure occurs between the two concrete mixtures also indicated that the addition of dispersed sawdust resulted to weaker CBGM samples. Upon increasing input energy from

  16. Chemical interaction of fresh and saline waters with compacted bentonite

    International Nuclear Information System (INIS)

    Muurinen, A.; Lehikoinen, J.; Melamed, A.; Pitkaenen, P.

    1996-01-01

    The interaction of compacted sodium bentonite with fresh and saline ground-water simulant was studied. The parameters varied in the experiments were the compositions of the solutions and oxygen and carbon dioxide content in the surroundings. The main interests of the study were the chemical changes in the experimental solution, bentonite porewater and bentonite together with the microstructural properties of bentonite. The major processes with fresh water were the diffusion of sodium, potassium, sulphate, bicarbonate and chloride from bentonite to the solution, and the diffusion of calcium and magnesium from the solution into bentonite. The major processes in the experiments with saline water were the diffusion of the sodium, magnesium, sulphate and bicarbonate from bentonite into the solution, and the diffusion of calcium from the solution into bentonite

  17. Sorption and diffusion of FE(II) in bentonite

    International Nuclear Information System (INIS)

    Muurinen, A.; Tournassat, C.; Hadi, J.; Greneche, J.-M.

    2014-02-01

    The iron in the engineering barrier system of a nuclear waste repository interacts via the corrosion process with the swelling clay intended as the buffer material. This interaction may affect the sealing properties of the clay. In the case of iron-bentonite interaction, redox reactions, dissolution/precipitation, the diffusion and sorption are coupled together. In a combined study different processes are difficult to distinguish from each other, and more specific studies are needed for the separate processes. In particular, there is a need for well-controlled diffusion and sorption experiments where iron is kept as Fe(II). In this project, sorption and diffusion of Fe(II) in bentonite have been studied. The experiments were carried out under low-oxygen conditions in an anaerobic glove-box. The radioactive isotope ( 55 Fe) was used as a tracer in the experiments. The sorption experiments were carried out with two batches of purified MX-80 bentonite. One was purified at Bureau de Recherches Geologiques et Minieres, French Geological Survey (BRGM) and the other one at VTT Technical Research Centre of Finland (VTT). Experiments were also carried out with synthetic smectite, which did not include iron, which was prepared at LMPC (ENSC, F 68093 Mulhouse, France). The sorption experiments were carried out in 0.3 M and 0.05 M NaCl solutions as a function of pH, and in 0.3 M NaCl solution buffered at pH 5 as a function of added Fe(II) concentration. The separation of bentonite and solution at the end of the sorption experiment was carried out in the early phase by centrifuging only. In the later phase, ultrafiltering was added in order to improve the separation. The diffusion experiments were carried out in compacted samples prepared from MX-80 purified at VTT and saturated with 0.3 M NaCl at pH 8 and 5. A non-steady-state diffusion experiment method, where the tracer was introduced as an impulse source between two bentonite plugs was used in the measurements

  18. Sorption and diffusion of FE(II) in bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Muurinen, A. [VTT Technical Research Centre of Finland, Espoo (Finland); Tournassat, C.; Hadi, J. [BRGM, Orleans (France); Greneche, J.-M. [LPCE, Le Mans (France)

    2014-02-15

    The iron in the engineering barrier system of a nuclear waste repository interacts via the corrosion process with the swelling clay intended as the buffer material. This interaction may affect the sealing properties of the clay. In the case of iron-bentonite interaction, redox reactions, dissolution/precipitation, the diffusion and sorption are coupled together. In a combined study different processes are difficult to distinguish from each other, and more specific studies are needed for the separate processes. In particular, there is a need for well-controlled diffusion and sorption experiments where iron is kept as Fe(II). In this project, sorption and diffusion of Fe(II) in bentonite have been studied. The experiments were carried out under low-oxygen conditions in an anaerobic glove-box. The radioactive isotope ({sup 55}Fe) was used as a tracer in the experiments. The sorption experiments were carried out with two batches of purified MX-80 bentonite. One was purified at Bureau de Recherches Geologiques et Minieres, French Geological Survey (BRGM) and the other one at VTT Technical Research Centre of Finland (VTT). Experiments were also carried out with synthetic smectite, which did not include iron, which was prepared at LMPC (ENSC, F 68093 Mulhouse, France). The sorption experiments were carried out in 0.3 M and 0.05 M NaCl solutions as a function of pH, and in 0.3 M NaCl solution buffered at pH 5 as a function of added Fe(II) concentration. The separation of bentonite and solution at the end of the sorption experiment was carried out in the early phase by centrifuging only. In the later phase, ultrafiltering was added in order to improve the separation. The diffusion experiments were carried out in compacted samples prepared from MX-80 purified at VTT and saturated with 0.3 M NaCl at pH 8 and 5. A non-steady-state diffusion experiment method, where the tracer was introduced as an impulse source between two bentonite plugs was used in the measurements

  19. Mechanical stability of bentonite buffer system for high level nuclear waste

    Energy Technology Data Exchange (ETDEWEB)

    Lempinen, A. [Helsinki Univ. of Technology, Espoo (Finland). Lab. of Theoretical and Applied Mechanics

    1998-05-01

    According to present plans, high level nuclear waste in Finland is going to be disposed of in bedrock at a depth of several hundred metres. The spent fuel containers will be placed in boreholes drilled in the floors of deposition tunnels with engineered clay buffer, which is made of bentonite blocks. The tunnels will be filled with a mixture of bentonite and crushed rock. For stability calculations a thermomechanical model for compressed bentonite is needed. In the study a thermomechanically consistent model for reversible processes for swelling clays is presented. Preliminary calculations were performed and they show that uncertainty in material parameter values causes significantly different results. Therefore, measurements that are consistent with the model are needed 12 refs.

  20. Mechanical stability of bentonite buffer system for high level nuclear waste

    International Nuclear Information System (INIS)

    Lempinen, A.

    1998-05-01

    According to present plans, high level nuclear waste in Finland is going to be disposed of in bedrock at a depth of several hundred metres. The spent fuel containers will be placed in boreholes drilled in the floors of deposition tunnels with engineered clay buffer, which is made of bentonite blocks. The tunnels will be filled with a mixture of bentonite and crushed rock. For stability calculations a thermomechanical model for compressed bentonite is needed. In the study a thermomechanically consistent model for reversible processes for swelling clays is presented. Preliminary calculations were performed and they show that uncertainty in material parameter values causes significantly different results. Therefore, measurements that are consistent with the model are needed

  1. Evaluation of gas migration characteristics of compacted bentonite and Ca-bentonite mixture

    International Nuclear Information System (INIS)

    Tanaka, Yukihisa; Hironaga, Michihiko

    2014-01-01

    In the current concept of subsurface disposal and near-surface pit disposal for low level radioactive waste, compacted bentonite and Ca-bentonite mixture will be used as an engineered barrier mainly for inhibiting migration of radioactive nuclides, respectively. Hydrogen gas can be generated inside the engineered barrier of subsurface disposal facilities mainly by anaerobic corrosion of metals used for containers, etc. Hydrogen gas can be also generated inside the engineered barrier of near-surface pit disposal facilities mainly by the chemical interaction between aluminum and the alkaline component of cement, or water. If the gas generation rate exceeds the diffusion rate of gas molecules inside of the compacted bentonite and Ca-bentonite mixture, gas will accumulate in the void space inside of the compacted bentonite and Ca-bentonite mixture until breakthrough occurs. It is expected to be not easy for gas to entering into the compacted bentonite mixture as a discrete gaseous phase because the pore of the compacted bentonite and Ca-bentonite mixture is so minute. Therefore in this study, the gas migration characteristics and the effect of gas migration on the hydraulic conductivity of the compacted bentonite and Ca-bentonite mixture are investigated by the gas migration tests. The applicability of the two phase flow model without considering deformability of the specimen is investigated. The applicability of the model of two phase flow through deformable porous media, which was originally developed by CRIEPI, is also investigated. Results of this study imply that : (1) Gas migration mechanism of the compacted bentonite and Ca-bentonite mixture is revealed through gas migration test. (2) Hydraulic conductivity measured after the large gas breakthrough is substantially the same that measured before the gas migration test. (3) Stress change, pore-water pressure change and volume change of the specimen during the gas migration test can be reproduced by the numerical

  2. Retention of cesium by alkylammonium salt modified bentonite: experiments and modeling

    International Nuclear Information System (INIS)

    Lin, Shih-Min; Chen, Jiann-Ruey; Wang, Tsing-Hai; Teng, Shi-Ping

    2010-01-01

    Document available in extended abstract form only. Application of bentonite as engineering barriers as well as back-filled material to radioactive waste repository is widely conducted around the world. It was reported that organic-modified bentonite is able to adsorb anionic radionuclides but its sorptive capabilities toward cationic radionuclides would decrease at the same time. In order to evaluate the influence of alkyl moiety of modification reagents on sorption of cationic radionuclides, surface modification of bentonite by hexadecyltrimethyl ammonium (HTMA, 3 deg.) and by hexa-decylamine (Hamine, 1 deg.) was prepared. Their sorption capabilities were examined by Cs sorption experiments and quantified as sorption equilibrium constants (in terms of log K) by using surface complexation model MINEQL+ 4.6. In order of the decrease of sorption capability, it is observed that MX 80 > Hamine-modified > HTMA-modified bentonite. Moreover, similar to the performance of MX 80, Hamine-modified bentonite reached a sorption plateau under alkaline environments while HTMA-modified one seemed to be insensitive to the pH variation. To explain the observations, it was assumed that Cs sorption was mainly contributed by structure (= X) and edge (= SOH) sorption sites on bentonite surfaces. It was observed that the log K of structure sites of both Hamine- and HTMA-modified bentonite was more negative than that of raw bentonite. It was taken as evidence that either Hamine or HTMA species were less capable of exchanging with Cs ions than Na ions (exchangeable cation on MX 80 surfaces) do. This also implied that the sorption affinity of Hamine was greater than HTMA toward structure sites. However, it was difficult to explain the influence of organic modification on sorption at edge sorption sites. The HTMA-modified bentonite had the most negative log K value, while Hamine-modified one showed the least negative log K. it could be only explained by the structure changes of the organo

  3. Preparation and characterization of bentonite organo clay; Preparacao de caracterizacao de argilas bentonitas organofilicas

    Energy Technology Data Exchange (ETDEWEB)

    Bertagnolli, C.; Almeida Neto, A.F. [Universidade Estadual de Campinas (UNICAMP), SP (Brazil). Fac. de Engenharia Quimica. Lab. de Engenharia Ambiental; Silva, M.G.C., E-mail: meuris@feq.unicamp.b [Universidade Estadual de Campinas (UNICAMP), SP (Brazil). Fac. de Engenharia Quimica

    2009-07-01

    Bentonite clays organically modified have great potential use for environmental remediation, especially in the separation of organic compounds from the water. The aim of this work was the preparation of organophilic clays from 'Verde-Lodo' bentonite clay with the quaternary ammonium salts cetyl-pyridinium chloride and benzalkonium chloride. The materials obtained were characterized by XRD, thermogravimetric analyses, Helium picnometry, SEM and energy dispersive X-ray techniques. The results show consistently successful synthesis of the organoclay through the increase in the basal spacing, as well as salt elimination picks and presence of carbon and chlorine in the modified clays; they are inexistent elements in the natural clay. (author)

  4. Morphology study of polyamide 6/bentonite clay nanocomposites

    International Nuclear Information System (INIS)

    Paz, Rene A.; Araujo, Edcleide M.; Melo, Tomas J.A.; Leite, Amanda M.D.; Medeiros, Vanessa Nobrega; Pessan, Luiz A.; Passador, Fabio R.

    2011-01-01

    Polymer/clay nanocomposites have had much attention in recent years, especially those developed with layered silicates, due to the need for engineering materials more efficient than pure polymers for certain applications. The level of exfoliation of layered silicates in the crystalline structure of polymer matrices has been studied and it has been observed that it affects the behavior of crystalline and therefore the mechanical and physical properties. In this study, polyamide 6 nanocomposites were obtained by the melt intercalation technique, using regional bentonite clay modified with a quaternary ammonium salt in an amount of 3% by weight. XRD and TEM tests showed obtaining nanocomposites with exfoliated structures (author)

  5. DISCHARGE VALVE FOR GRANULAR MATERIAL

    Science.gov (United States)

    Stoughton, L.D.; Robinson, S.T.

    1962-05-15

    A gravity-red dispenser or valve is designed for discharging the fueled spherical elements used in a pebble bed reactor. The dispenser consists of an axially movable tube terminating under a hood having side walls with openings. When the tube is moved so that its top edge is above the tops of the side openings the elements will not flow. As the tube is moved downwardly, the elements flow into the hood through the side openings and over the top edge into the tube at an increasing rate as the tube is lowered further. The tube is spaced at all times from the hood and side walls a distance greater than the diameter of the largest element to prevent damaging of the elements when the dispenser is closed to flow. (AEC)

  6. Properties of the bentonite from Lieskovec deposit and their possible environmental applications

    International Nuclear Information System (INIS)

    Andrejkovicova, S.

    2008-01-01

    The community increasingly focuses on broader uses of raw materials, occurring in relatively sufficient amounts. Among them, bentonite play very important role in the environmental applications. Results presented herein are related to the yet comprehensively unexplored Fe-rich bentonite from Lieskovec deposit, Central Slovakia. The objective of this study was complex investigation of Lieskovec bentonite deposit. This bentonite was developed from andesitic pyroclastics; the dominant mineral in all the samples is iron-rich montmorillonite, covering 29 to 56 mass % in the samples. The accessory minerals include kaolinite (5-17 mass %), quartz (3-28 mass %), muscovite/illite (3-16 mass %), volcanic glass (6-14 mass %), orthoclase (1-12 mass %), opal (1-8 mass %) and cristobalite (1-3 mass %). Structural Fe(III) is mainly in phyllosilicates accounting for 70 % to 90 % of the total Fe in the unfractionated samples; less than 5 % is Fe(II). The remainder of the Fe is present in oxide and/or oxyhydroxide phases dominated by poorly ordered goethite and hematite with possibly some maghemite. Basic properties of bentonites result from the structure of the smectites. Size fractionation did not lead to pure smectite. Kaolinite and mica were not successfully removed. Quartz and feldspars were dismantled effectively. Non-clay minerals contribution decreased. Smectite content increased after separation up to 75 mass %. Low cation exchange capacities between 35 and 61 meq/100 g are caused also by low magnesium content in the octahedral sheets of montmorillonite, suggesting lower isomorphic Mg for Al substitution in the octahedral sheets of smectite and thus its lower octahedral charge. The main factor influencing CECs is smectite content affecting dominantly also the geotechnical properties. Geotechnical properties of Lieskovec bentonite, such as liquid limit in range 64-80 % and water adsorption by Enslin test 123-265 % were insufficient for utilization in geo-synthetic clay

  7. BaM bentonite and some of its properties

    International Nuclear Information System (INIS)

    Matal, Oldřich; Vávra Michal; Kachlík, Martin; Maca, Karel; Kotnour, Petr; Pospíšková, Ilona

    2018-01-01

    BaM bentonite is lime-magnesium bentonite of domestic origin. Its properties were measured experimentally with focus on the following parameters: composition, morphology and particle size distribution, powder bulk density, powder pressing parameters, shear strength, and water saturation. The findings will find use in nuclear safety assessments of engineered bentonite barriers in underground nuclear waste disposal facilities. (orig.)

  8. Investigation of Erosion of Cement-Bentonite via Piping

    Directory of Open Access Journals (Sweden)

    Zijun Wang

    2017-01-01

    Full Text Available Cement-bentonite is one of the main materials used in the seepage barriers to protect earth dams and levees from water erosion. However, the current understanding of the erodibility of the cementitious materials and the interactions between cracked seepage barriers and the water flow is inadequate. Based on the laboratory pinhole erosion test, we first investigated the impacts of cement-bentonite treatments by using the ground granulated blast-furnace slag (GGBS as replacement on the erosion characteristics, compared with the original mixtures; the inclusion of GGBS highlighted a potential advantage against water erosion. In addition, we proposed to calculate the erosion percentage and establish the mathematical relationships between the erosion percentage and different regimes, that is, different curing period, erosion time, and sizes of initial holes. Results showed that enough curing period was critical to avoid the increases of hydraulic conductivity in the macrofabric of the barrier; meanwhile, the materials were eroded quickly at the beginning and slowed down with the erosion time, where the enlargement of the initial creaks would be stabilised at some point in time. Moreover, the sizes of initial holes may affect the erosion situation varying from the sample curing periods.

  9. Anisotropy in cohesive, frictional granular media

    International Nuclear Information System (INIS)

    Luding, Stefan

    2005-01-01

    The modelling of cohesive, frictional granular materials with a discrete particle molecular dynamics is reviewed. From the structure of the quasi-static granular solid, the fabric, stress, and stiffness tensors are determined, including both normal and tangential forces. The influence of the material properties on the flow behaviour is also reported, including relations between the microscopic attractive force and the macroscopic cohesion as well as the dependence of the macroscopic friction on the microscopic contact friction coefficient. Related to the dynamics, the anisotropy of both structure and stress are exponentially approaching the maximum

  10. Evaluation of long-term interaction between cement and bentonite for geological disposal (1) - Project Overview

    International Nuclear Information System (INIS)

    Owada, Hitoshi; Hayashi, Daisuke; Yahagi, Ryoji; Ishii, Tomoko

    2012-01-01

    Document available in extended abstract form only. Bentonitic and cementitious materials are both planned for use as engineered barrier materials in the geological disposal of high level vitrified waste and TRU (transuranic) waste in Japan. As shown in Figure 1, bentonitic material will be placed around the waste packages as buffer material and a large amount of cementitious material is specified for use as filler, structure, support and grout. Cementitious material supplies an alkaline solution with high calcium concentration through reaction with groundwater. However, the alkaline solution will cause chemical and physical alteration of the bentonitic material. Since many important functions of an engineered barrier system (EBS), such as watertightness, chemical buffering, and sorption of radioactive nuclides, will be maintained by the properties of the buffer material, evaluation of long-term chemical or mechanical alteration of the buffer material is necessary to demonstrate the robustness of the EBS. Although many researches on chemical and mechanical alteration of bentonitic material, there was large uncertainty because the chemical alteration of bentonitic material is very slow and the altered region is very limited. In this project, the dissolution rate of montmorillonite under compaction and the spatial distribution of secondary C-S-H precipitation were obtained and mechanical and hydrological changes caused by the mineralogical change of bentonite material were modeled to reduce the uncertainty in the safety assessment of EBS performance. To improve the accuracy of the long term evaluation of the EBS performance, coupled analyses between hydraulic/mechanical calculations and geochemical-mass transport coupled calculations were performed. Alteration of mechanical properties caused by chemical degradation should be modeled for the coupled calculations. Because the mechanical properties of bentonitic material depend strongly on the montmorillonite content and

  11. Dynamic Deformation and Collapse of Granular Columns

    Science.gov (United States)

    Uenishi, K.; Tsuji, K.; Doi, S.

    2009-12-01

    Large dynamic deformation of granular materials may be found in nature not only in the failure of slopes and cliffs — due to earthquakes, rock avalanches, debris flows and landslides — but also in earthquake faulting itself. Granular surface flows often consist of solid grains and intergranular fluid, but the effect of the fluid may be usually negligible because the volumetric concentration of grains is in many cases high enough for interparticle forces to dominate momentum transport. Therefore, the investigation of dry granular flow of a mass might assist in further understanding of the above mentioned geophysical events. Here, utilizing a high-speed digital video camera system, we perform a simple yet fully-controlled series of laboratory experiments related to the collapse of granular columns. We record, at an interval of some microseconds, the dynamic transient granular mass flow initiated by abrupt release of a tube that contains dry granular materials. The acrylic tube is partially filled with glass beads and has a cross-section of either a fully- or semi-cylindrical shape. Upon sudden removal of the tube, the granular solid may fragment under the action of its own weight and the particles spread on a rigid horizontal plane. This study is essentially the extension of the previous ones by Lajeunesse et al. (Phys. Fluids 2004) and Uenishi and Tsuji (JPGU 2008), but the striped layers of particles in a semi-cylindrical tube, newly introduced in this contribution, allow us to observe the precise particle movement inside the granular column: The development of slip lines inside the column and the movement of particles against each other can be clearly identified. The major controlling parameters of the spreading dynamics are the initial aspect ratio of the granular (semi-)cylindrical column, the frictional properties of the horizontal plane (substrate) and the size of beads. We show the influence of each parameter on the average flow velocity and final radius

  12. SAXS and TEM Investigation of Bentonite Structure

    International Nuclear Information System (INIS)

    Matusewicz, Michal; Liljestroem, Ville; Muurinen, Arto; Serimaa, Ritva

    2013-01-01

    A preliminary investigation of bentonite structure using Small-Angle X-ray Scattering (SAXS) and Transmission Electron Microscopy (TEM) is presented. Three types of clay were used: unchanged MX-80 bentonite and purified clays with sodium or calcium ions. Quantitative information in nano-scale - basal spacing, mean crystallite size - was obtained from SAXS, which was complemented by TEM to give qualitative information from micron to nanometre scale. SAXS seems to be a more reliable source of quantitative data than TEM. SAXS gives the averaged information about basal spacing. TEM in this study gives more qualitative information, but in a greater resolution range. The presented work is a starting point to combine more methods to obtain a better idea of bentonite structure. (authors)

  13. Bentonite reactivity in alkaline solutions: results of the Cyprus natural analogue project (CNAP)

    International Nuclear Information System (INIS)

    Alexander, W.R.; Milodowski, A.E.; Pitty, A.F.; Hardie, S.M.L.; Korkeakoski, P.; Norris, S.; Puigdomenech, I.; Sellin, P.; Rigas, M.

    2012-01-01

    Document available in extended abstract form only. Bentonite is one of the most safety-critical components of the engineered barrier system in the disposal concepts developed for many types of radioactive waste. Bentonite is used due to its favourable properties (including plasticity, swelling capacity, colloid filtration, low hydraulic conductivity, high retardation of key radionuclides) and its stability in relevant geological environments. However, bentonite is unstable under alkaline conditions and, due to the fact that cementitious materials react with groundwater to produce initial leachates with pH >13 (later falling to around pH 12.5), this has driven recent interest in low alkali cements, because the pH of the leachate is somewhat lower than standard OPC (Ordinary Portland Cement), lying around pH 10-11. It is hoped that this lower pH will reduce bentonite reaction, so allowing the use of low alkali cements in close proximity with bentonite. Assuring the long-term stability of bentonite in contact with such alkaline fluids under conditions representative of a deep geological repository requires complementary laboratory, modelling and in situ studies. In particular, to build a robust safety case, it is important to have supporting natural analogue data to confirm understanding - and validate models - of the likely long-term performance of bentonite. As a result of a review of the available literature and recent geological investigations by the authors, several sites in Cyprus were selected as particularly promising for this purpose. All alkaline groundwaters studied so far in Cyprus originate from ophiolite host rocks which are wide-spread across the island. The alkaline pH values (generally between pH 10 and 11, but a maximum of 12 has been observed) reported in the groundwaters are a product of the serpentinization of the ophiolites. The presence of bentonite and other clay-rich rocks in close proximity to the natural alkaline groundwaters permits the

  14. Granular motor in the non-Brownian limit

    NARCIS (Netherlands)

    Oyarte Galvez, Loreto Alejandra; van der Meer, Roger M.

    2016-01-01

    In this work we experimentally study a granular rotor which is similar to the famous Smoluchowski–Feynman device and which consists of a rotor with four vanes immersed in a granular gas. Each side of the vanes can be composed of two different materials, creating a rotational asymmetry and turning

  15. Granular Leidenfrost effect: Experiment and theory of floating particle clusters

    NARCIS (Netherlands)

    Eshuis, Peter; Eshuis, P.G.; van der Meer, Roger M.; van der Weele, J.P.; Lohse, Detlef

    2005-01-01

    Granular material is vertically vibrated in a 2D container: above a critical shaking strength, and for a sufficient number of beads, a crystalline cluster is elevated and supported by a dilute gaseous layer of fast beads underneath. We call this phenomenon the granular Leidenfrost effect. The

  16. USE OF GRANULAR GRAPHITE FOR ELECTROLYTIC DECHLORINATION OF TRICHLOROETHYLENE

    Science.gov (United States)

    Granular graphite is a potential electrode material for the electrochemical remediation of refractory chlorinated organic compounds such as trichloroethylene (TCE). However, the use of granular graphite can complicate the experimental results. On one hand, up to 99% of TCE was re...

  17. Surface instabilities in shock loaded granular media

    Science.gov (United States)

    Kandan, K.; Khaderi, S. N.; Wadley, H. N. G.; Deshpande, V. S.

    2017-12-01

    The initiation and growth of instabilities in granular materials loaded by air shock waves are investigated via shock-tube experiments and numerical calculations. Three types of granular media, dry sand, water-saturated sand and a granular solid comprising PTFE spheres were experimentally investigated by air shock loading slugs of these materials in a transparent shock tube. Under all shock pressures considered here, the free-standing dry sand slugs remained stable while the shock loaded surface of the water-saturated sand slug became unstable resulting in mixing of the shocked air and the granular material. By contrast, the PTFE slugs were stable at low pressures but displayed instabilities similar to the water-saturated sand slugs at higher shock pressures. The distal surfaces of the slugs remained stable under all conditions considered here. Eulerian fluid/solid interaction calculations, with the granular material modelled as a Drucker-Prager solid, reproduced the onset of the instabilities as seen in the experiments to a high level of accuracy. These calculations showed that the shock pressures to initiate instabilities increased with increasing material friction and decreasing yield strain. Moreover, the high Atwood number for this problem implied that fluid/solid interaction effects were small, and the initiation of the instability is adequately captured by directly applying a pressure on the slug surface. Lagrangian calculations with the directly applied pressures demonstrated that the instability was caused by spatial pressure gradients created by initial surface perturbations. Surface instabilities are also shown to exist in shock loaded rear-supported granular slugs: these experiments and calculations are used to infer the velocity that free-standing slugs need to acquire to initiate instabilities on their front surfaces. The results presented here, while in an idealised one-dimensional setting, provide physical understanding of the conditions required to

  18. A Numerical Investigation on the Effect of Gas Pressure on the Water Saturation of Compacted Bentonite-Sand Samples

    Directory of Open Access Journals (Sweden)

    Jiang-Feng Liu

    2017-01-01

    Full Text Available In deep geological disposal for high-level radioactive waste, the generated gas can potentially affect the sealing ability of bentonite buffers. There is a competition between water and gas: the former provides sealing by swelling bentonite, and the latter attempts to desaturate the bentonite buffer. Thus, this study focused on numerically modelling the coupling effects of water and gas on the water saturation and sealing efficiency of compacted bentonite-sand samples. Different gas pressures were applied to the top surface of an upper sample, whereas the water pressure on the bottom side of the lower sample was maintained at 4 MPa. The results indicated that gas pressure did not significantly affect the saturation of the bentonite-sand sample until 2 MPa. At 2 MPa, the degree of water saturation of the upper sample was close to 1.0. As the gas pressure increased, this influence was more apparent. When the gas pressure was 6 MPa or higher, it was difficult for the upper sample to become fully saturated. Additionally, the lower sample was desaturated due to the high gas pressure. This indicated that gas pressure played an important role in the water saturation process and can affect the sealing efficiency of bentonite-based buffer materials.

  19. Summary of a GAMBIT Club Workshop on Gas Migration in Bentonite. A Report produced for the GAMBIT Club

    International Nuclear Information System (INIS)

    Rodwell, W.R.

    2005-11-01

    In order to review the status of understanding of gas migration in bentonite, and particularly the experimental data that provides the basis for such understanding as exists, the GAMBIT Club organised a workshop of invited participants that was held in Madrid during 29-30 October 2003. (The GAMBIT Club is a consortium of radioactive waste management agencies: SKB, ANDRA, Enresa, JNC, Nagra, and Posiva.) The motivation for the workshop was the difficulty found in developing models of gas migration in bentonite because of lack of detailed characterisation of its mechanism and controlling parameters. This report provides a summary of the presentations made at the workshop and of the discussions that took place. Copies of the slides presented are provided in the appendix. The titles of the presentations are: Overview of Current Status of Experimental Knowledge and Understanding of Gas migration in Bentonite (William Rodwell); Summary of GAMBIT Club Modelling of Gas Migration in Compacted Bentonite (William Rodwell); A Capillarity/advection Model for Gas Break-through Pressures (Marolo Alfaro, Jim Graham); Recent Experiments by JNC on Gas Migration in Bentonite (Kenji Tanai, Mikihiko Yamamoto); Gas Flow in Clays: Experimental Data Leading to Two-phase and Preferential-path Modelling (Eduardo Alonso); Gas Movement in MX80 Bentonite under Constant Volume Conditions (Jon Harrington, Steve Horseman); Some Practical Observations on Gas Flow in Clays and Clay-rich Rocks (Steve Horseman, Jon Harrington); Early Large-scale Experiments on Gas Break-through Pressures in Clay based Materials (Harald Hoekmark)

  20. Summary of a GAMBIT Club Workshop on Gas Migration in Bentonite. A Report produced for the GAMBIT Club

    Energy Technology Data Exchange (ETDEWEB)

    Rodwell, W.R. [Serco Assurance, Risley (GB)] (ed.)

    2005-11-15

    In order to review the status of understanding of gas migration in bentonite, and particularly the experimental data that provides the basis for such understanding as exists, the GAMBIT Club organised a workshop of invited participants that was held in Madrid during 29-30 October 2003. (The GAMBIT Club is a consortium of radioactive waste management agencies: SKB, ANDRA, Enresa, JNC, Nagra, and Posiva.) The motivation for the workshop was the difficulty found in developing models of gas migration in bentonite because of lack of detailed characterisation of its mechanism and controlling parameters. This report provides a summary of the presentations made at the workshop and of the discussions that took place. Copies of the slides presented are provided in the appendix. The titles of the presentations are: Overview of Current Status of Experimental Knowledge and Understanding of Gas migration in Bentonite (William Rodwell); Summary of GAMBIT Club Modelling of Gas Migration in Compacted Bentonite (William Rodwell); A Capillarity/advection Model for Gas Break-through Pressures (Marolo Alfaro, Jim Graham); Recent Experiments by JNC on Gas Migration in Bentonite (Kenji Tanai, Mikihiko Yamamoto); Gas Flow in Clays: Experimental Data Leading to Two-phase and Preferential-path Modelling (Eduardo Alonso); Gas Movement in MX80 Bentonite under Constant Volume Conditions (Jon Harrington, Steve Horseman); Some Practical Observations on Gas Flow in Clays and Clay-rich Rocks (Steve Horseman, Jon Harrington); Early Large-scale Experiments on Gas Break-through Pressures in Clay based Materials (Harald Hoekmark)

  1. Bentonite deposits as a natural analogue to long-term barriers in a final repository of nuclear waste

    International Nuclear Information System (INIS)

    Keto, P.

    2000-01-01

    The geology of bentonite occurrences in Almeria (Spain) and Wyoming (USA) were studied in order to find suitable natural analogue to the longterm mechanical behaviour of the bentonite barrier in the final nuclear waste disposal. The study is based on literature review over both occurrence areas and on fieldwork observations from Almeria, Spain. The deposit areas differ from each other by age, deposition environment, exchangeable cation chemistry, alteration condition, occurrence and deformational features. One of the most important deformational feature in Almeria bentonites was the existence of Tertiary (Middle and Upper Miocene, 6-15.5 Ma old) bentonite intrusion inside/over younger Quaternary (Pleistocene Superior, 0.01-0.72 Ma old) sediments. This was a result of the confining pressure of overlying volcanic rocks and sediments and the high plasticity behaviour of bentonites. According to this observation, the pressure effect in final nuclear waste repositories requires further investigations. The bentonites in Wyoming have survived weathering and shearing without losing their expandability or other properties typical of smectite-rich materials. (orig.)

  2. Sorption of natural uranium by algerian bentonite

    International Nuclear Information System (INIS)

    Megouda, N.; Kadi, H.; Hamla, M.S.; Brahimi, H.

    2004-01-01

    Full text.Batch sorption experiments have been used to assess the sorption behaviour of uranium onto natural and drilling bentonites. The operating parameters (pH, aolis-liquid ratio, particle size, time and initial uranium concentration) influenced the rate of adsorption. The distribution coefficient (Kd) range values at equilibrium time are 45.95-1079.26 ml/g and 32.81-463053 ml/g for the drilling and natural bentonites respectively. The equilibrium isotherms show that the data correlate with both Freundlich and Langmuir models

  3. Ion diffusion in compacted bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Lehikoinen, J. [VTT Chemical Technology, Espoo (Finland)

    1999-03-01

    In the study, a two-dimensional molecular-level diffusion model, based on a modified form of the Gouy-Chapman (GC) theory of the electrical double layers, for hydrated ionic species in compacted bentonite was developed. The modifications to the GC theory, which forms the very kernel of the diffusion model, stem from various non-conventional features: ionic hydration, dielectric saturation, finite ion-sizes and specific adsorption. The principal objectives of the study were met. With the aid of the consistent diffusion model, it is a relatively simple matter to explain the experimentally observed macroscopic exclusion for anions as well as the postulated, but greatly controversial, surface diffusion for cations. From purely theoretical grounds, it was possible to show that the apparent diffusivities of cations, anions and neutral molecules (i) do not exhibit order-or-magnitude differences, and (ii) are practically independent of the solution ionic strength used and, consequently, of the distribution coefficient, K{sub d}, unless they experience specific binding onto the substrate surface. It was also of interest to investigate the equilibrium anionic concentration distribution in the pore geometry of the GMM model as a function of the solution ionic strength, and to briefly speculate its consequences to diffusion. An explicit account of the filter-plate effect was taken by developing a computerised macroscopic diffusion model, which is based upon the very robust and efficient Laplace Transform Finite-Difference technique. Finally, the inherent limitations as well as the potential fields of applications of the models were addressed. (orig.) 45 refs.

  4. Ion diffusion in compacted bentonite

    International Nuclear Information System (INIS)

    Lehikoinen, J.

    1999-03-01

    In the study, a two-dimensional molecular-level diffusion model, based on a modified form of the Gouy-Chapman (GC) theory of the electrical double layers, for hydrated ionic species in compacted bentonite was developed. The modifications to the GC theory, which forms the very kernel of the diffusion model, stem from various non-conventional features: ionic hydration, dielectric saturation, finite ion-sizes and specific adsorption. The principal objectives of the study were met. With the aid of the consistent diffusion model, it is a relatively simple matter to explain the experimentally observed macroscopic exclusion for anions as well as the postulated, but greatly controversial, surface diffusion for cations. From purely theoretical grounds, it was possible to show that the apparent diffusivities of cations, anions and neutral molecules (i) do not exhibit order-or-magnitude differences, and (ii) are practically independent of the solution ionic strength used and, consequently, of the distribution coefficient, K d , unless they experience specific binding onto the substrate surface. It was also of interest to investigate the equilibrium anionic concentration distribution in the pore geometry of the GMM model as a function of the solution ionic strength, and to briefly speculate its consequences to diffusion. An explicit account of the filter-plate effect was taken by developing a computerised macroscopic diffusion model, which is based upon the very robust and efficient Laplace Transform Finite-Difference technique. Finally, the inherent limitations as well as the potential fields of applications of the models were addressed. (orig.)

  5. Selfinjection of highly compacted bentonite into rock joints

    International Nuclear Information System (INIS)

    Pusch, R.

    1978-02-01

    When radioactive waste is disposed in bore holes in rocks there will be some space between rock and canister. Other investigations have suggested that the space could be filled with highly compacted bentonite. In this report it is discussed if open joints formed or widened in the surrounding rock after the deposition will be sealed by self-injecting bentonite. Bentonite in contact with water will swell. The flow pattern and properties of the swelling bentonite, the permeability of the extruded bentonite and the viscosity of the extruded bentonite have been investigated. The following statements are done. In the narrow joints that can possibly be opened by various processes, the rate of bentonite extrusion will be very slow except for the first few centimeter move, which may take place in a few mounths. The swelling pressure of the extruded bentonite will decrease rapidly with the distance from the deposition hole. The loss of bentonite extruded through the narrow joints will be negligible. In the outer part of the bentonite zone there will be a successive transition to a very soft, dilute bentonite suspension. It will consist of fairly large particle aggregates which will be stuck where the joint width decreases

  6. Adsorption behaviour of bivalent ions onto Febex bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Missana, T.; Garcia-Gutierrez, M. [Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas (CIEMAT), Dpt. de Impacto Ambiental de la Energia Madrid (Spain)

    2005-07-01

    The sorption and transport properties of radionuclides in the near and far field barriers of a deep geological radioactive waste repository are amongst the principal aspects to be evaluated for the performance assessment (PA) of such a kind of disposal. The study of the clayey materials is crucial because the backfill material is constituted by compacted clay in most countries design; in addition, argillaceous formations are particularly suitable as host rock formations. It is widely recognised that, to acquire predictive modelling capability, a theoretical effort is needed for a mechanistic understanding of sorption processes, as they greatly influence the transport of radionuclides in clay porous structures. In this work, an exhaustive experimental study of the Co(II), Sr (II) and Ca(II) sorption behaviour on a Spanish bentonite was carried out. The clay used for these experiments is the FEBEX bentonite, which is basically formed by smectite (93 {+-} 2%) with small percentages of quartz (2 {+-} 1 %), plagioclase (3 {+-} 1 %), cristobalite (2 {+-} 1 %) and traces of minerals such as K-feldspar and calcite. (authors)

  7. Theoretical model of granular compaction

    Energy Technology Data Exchange (ETDEWEB)

    Ben-Naim, E. [Los Alamos National Lab., NM (United States); Knight, J.B. [Princeton Univ., NJ (United States). Dept. of Physics; Nowak, E.R. [Univ. of Illinois, Urbana, IL (United States). Dept. of Physics]|[Univ. of Chicago, IL (United States). James Franck Inst.; Jaeger, H.M.; Nagel, S.R. [Univ. of Chicago, IL (United States). James Franck Inst.

    1997-11-01

    Experimental studies show that the density of a vibrated granular material evolves from a low density initial state into a higher density final steady state. The relaxation towards the final density follows an inverse logarithmic law. As the system approaches its final state, a growing number of beads have to be rearranged to enable a local density increase. A free volume argument shows that this number grows as N = {rho}/(1 {minus} {rho}). The time scale associated with such events increases exponentially e{sup {minus}N}, and as a result a logarithmically slow approach to the final state is found {rho} {infinity} {minus}{rho}(t) {approx_equal} 1/lnt.

  8. Granular computing: perspectives and challenges.

    Science.gov (United States)

    Yao, JingTao; Vasilakos, Athanasios V; Pedrycz, Witold

    2013-12-01

    Granular computing, as a new and rapidly growing paradigm of information processing, has attracted many researchers and practitioners. Granular computing is an umbrella term to cover any theories, methodologies, techniques, and tools that make use of information granules in complex problem solving. The aim of this paper is to review foundations and schools of research and to elaborate on current developments in granular computing research. We first review some basic notions of granular computing. Classification and descriptions of various schools of research in granular computing are given. We also present and identify some research directions in granular computing.

  9. Preparation of granular activated carbons from composite of powder activated carbon and modified β-zeolite and application to heavy metals removal.

    Science.gov (United States)

    Seyedein Ghannad, S M R; Lotfollahi, M N

    2018-03-01

    Heavy metals are continuously contaminating the surface and subsurface water. The adsorption process is an attractive alternative for removing the heavy metals because of its low cost, simple operation, high efficiency, and flexible design. In this study, influences of β-zeolite and Cu-modified β-zeolite on preparation of granular activated carbons (GACs) from a composite of powder activated carbon (PAC), methylcellulose as organic binder, bentonite as inorganic binder, and water were investigated. A number of granular samples were prepared by controlling the weight percentage of binder materials, PAC and zeolites as a reinforcing adsorbent. Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction techniques were employed to characterize zeolite, modified zeolite and produced GAC. The produced GACs were used as the adsorbent for removal of Zn +2 , Cd 2+ and Pb 2+ ions from aqueous solutions. The results indicated that the adsorption of metals ions depended on the pH (5.5) and contact time (30 min). Maximum adsorption of 97.6% for Pb 2+ , 95.9% for Cd 2+ and 91.1% for Zn +2 occurred with a new kind of GAC made of Cu-modified β-zeolite. The Zn +2 , Cd 2+ and Pb 2+ ions sorption kinetics data were well described by a pseudo-second order model for all sorbents. The Langmuir and Freundlich isotherm models were applied to analyze the experimental equilibrium data.

  10. Effective elasticity coefficients of native rocks and consolidated granular matter

    International Nuclear Information System (INIS)

    Schulz, Beatrix M.; Schulz, Michael

    2008-01-01

    The elastic coefficients of binary heterogeneous materials, such as several native rock materials or consolidated granular matter will be determined in terms of a perturbation expansion. Furthermore, in order to check the validity of the obtained results, these are compared with numerical investigations using Boole's model of randomly distributed spheres. Finally, we apply the results on several classes of native rocks and consolidated granular materials

  11. Characterization of natural bentonite by NMR

    International Nuclear Information System (INIS)

    Leite, Sidnei Q.M.; Dieguez, Lidia C.; Menezes, Sonia M.C.; San Gil, Rosane A.S.

    1993-01-01

    Solid state NMR as well as several other instrumental chemical analysis techniques were used in order to characterize two natural occurring bentonite. The methodology is described. The NMR spectra, together with the other used techniques suggest that the observed differences are due to iron inclusions in tetrahedral and octahedral sites

  12. Pemanfaatan Bentonite sebagai Media Pembumian Elektroda Batang

    Directory of Open Access Journals (Sweden)

    Winanda Riga Tamma

    2017-03-01

    Full Text Available Sistem pentanahan merupakan suatu sistem yang bertujuan untuk mengamankan sistem tenaga listrik dari gangguan ke tanah maupun gangguan hubung singkat. Pada sistem pentanahan yang baik, resistansi pentanahan harus bernilai dibawah lima ohm. Resistansi pentanahan bergantung pada berbagai aspek antara lain yaitu struktur tanah, kelembapan tanah, dan kandungan yang ada dalam tanah itu sendiri. Dalam pengujian pada penelitian ini akan dilakukan perbaikan pada tanah dengan mencampurkan bentonite ke dalam tanah sebagai media pentanahan. Pencampuran bentonite bertujuan agar mendapatkan nilai resistansi pentanahan yang baik sesuai dengan standar sistem pentanahan. Pengujian dilakukan menggunakan elektroda batang dan alat earth resistance tester dengan metode tiga titik dimana elektroda utama atau elektroda pengukuran diberikan treatment sesuai dengan kondisi yang telah ditentukan. Diharapkan pada pengujian ini akan diketahui dampak dari bentonite terhadap penurunan nilai resistansi pentanahan. Hasil pengujian menunjukkan bahwa dengan mencampurkan bentonite pada media pentanahan, resistansi pentanahan menjadi lebih baik. Meskipun tidak terlalu signifikan, rata-rata penurunan dari setiap masing-masing treatment adalah sebesar 2 ohm.

  13. Laboratory tests of bentonite stabilization of bottom sediments from a dam reservoir in relation to their usage in municipal solid waste landfill liners

    Directory of Open Access Journals (Sweden)

    Karolina Koś

    2016-09-01

    Full Text Available Geotechnical parameters of bottom sediments from a dam reservoir (Rzeszowski Reservoir, Poland with bentonite addition are presented in the paper. Tests were carried out in the aspect of the possible usage of sediments as a material for soil liners in Municipal Solid Waste Landfill. Mentioned sediments did not fulfilled the permeability and plasticity criteria defined for soils that can be used in liners. The bentonite addition caused, among other things, a decrease in permeability coefficient and increase in plasticity index. Based on the carried out tests it was stated that sediments with 6% addition of bentonite fulfil all requirements and can be used for liners in MSWL.

  14. International Workshop on Traffic and Granular Flow

    CERN Document Server

    Herrmann, Hans; Schreckenberg, Michael; Wolf, Dietrich; Social, Traffic and Granular Dynamics

    2000-01-01

    "Are there common phenomena and laws in the dynamic behavior of granular materials, traffic, and socio-economic systems?" The answers given at the international workshop "Traffic and Granular Flow '99" are presented in this volume. From a physical standpoint, all these systems can be treated as (self)-driven many-particle systems with strong fluctuations, showing multistability, phase transitions, non-linear waves, etc. The great interest in these systems is due to several unexpected new discoveries and their practical relevance for solving some fundamental problems of today's societies. This includes intelligent measures for traffic flow optimization and methods from "econophysics" for stabilizing (stock) markets.

  15. Granular Gas in a Periodic Lattice

    Science.gov (United States)

    Dorbolo, S.; Brandenbourger, M.; Damanet, F.; Dister, H.; Ludewig, F.; Terwagne, D.; Lumay, G.; Vandewalle, N.

    2011-01-01

    Glass beads are placed in the compartments of a horizontal square grid. This grid is then vertically shaken. According to the reduced acceleration [image omitted] of the system, the granular material exhibits various behaviours. By counting the number of beads in each compartment after shaking, it is possible to define three regimes. At low…

  16. Anomalous infrared absorption in granular superconductors

    International Nuclear Information System (INIS)

    Carr, G.L.; Garland, J.C.; Tanner, D.B.

    1983-01-01

    Granular superconductors are shown to have a far-infrared absorption that is larger when the samples are superconducting than when they are normal. By constrast, theoretical models for these materials predict that when the samples become superconducting, the absorption should decrease

  17. Random packing of colloids and granular matter

    NARCIS (Netherlands)

    Wouterse, A.

    2008-01-01

    This thesis deals with the random packing of colloids and granular matter. A random packing is a stable disordered collection of touching particles, without long-range positional and orientational order. Experimental random packings of particles with the same shape but made of different materials

  18. Deposition and shaking of dry granular piles

    NARCIS (Netherlands)

    Hasan, M.

    2003-01-01

    A friction force model describing reversible stick-slip transition during contact has been developed with the special purpose to simulate the deposition of granular material. A test with a mass on a conveyor belt kept in position by a spring shows that a numerical simulation of the dynamics of such

  19. Collapse of tall granular columns in fluid

    Science.gov (United States)

    Kumar, Krishna; Soga, Kenichi; Delenne, Jean-Yves

    2017-06-01

    Avalanches, landslides, and debris flows are geophysical hazards, which involve rapid mass movement of granular solids, water, and air as a multi-phase system. In order to describe the mechanism of immersed granular flows, it is important to consider both the dynamics of the solid phase and the role of the ambient fluid. In the present study, the collapse of a granular column in fluid is studied using 2D LBM - DEM. The flow kinematics are compared with the dry and buoyant granular collapse to understand the influence of hydrodynamic forces and lubrication on the run-out. In the case of tall columns, the amount of material destabilised above the failure plane is larger than that of short columns. Therefore, the surface area of the mobilised mass that interacts with the surrounding fluid in tall columns is significantly higher than the short columns. This increase in the area of soil - fluid interaction results in an increase in the formation of turbulent vortices thereby altering the deposit morphology. It is observed that the vortices result in the formation of heaps that significantly affects the distribution of mass in the flow. In order to understand the behaviour of tall columns, the run-out behaviour of a dense granular column with an initial aspect ratio of 6 is studied. The collapse behaviour is analysed for different slope angles: 0°, 2.5°, 5° and 7.5°.

  20. Cost effects of Cu powder and bentonite on the disposal costs of an HLW repository in

    International Nuclear Information System (INIS)

    Kim, Sung Ki; Lee, Min Soo; Lee, Jong Youl; Choi, Heui Joo; Choi, Jong Won

    2008-01-01

    This paper provides the cost effect results of Cu powder and bentonite on the disposal cost for an HLW repository in Korea. In the cost analysis for both of these cost drivers, the price of Cu powder and the bentonite can affect the canister cost and the bentonite cost of the disposal holes as well as backfilling cost of the tunnels, respectively. Finally, we found that the unit cost of Cu and bentonite was the dominant cost drivers for the surface and underground facilities of an HLW repository. Therefore, an optimization of a canister and the layout of a disposal hole and disposal tunnels are essential to decrease the direct disposal cost of spent fuels. The disposal costs can be largely divided into two parts such as a surface facilities' cost and an underground facilities' cost. According to the KRS' cost analysis, the encapsulation material as well as the buffering and backfilling cost were the significant costs. Especially, a canister's cost was approximately estimated to be more than one fourth of the overall disposal costs. So it can be estimated that the unit cost of Cu powder is an important cost diver. Because the outer shell of the canister was made of Cu powder by a cold spray coating method. In addition, the unit cost of bentonite can also affect the buffering and the backfilling costs of the disposal holes and the disposal tunnels. But, these material costs will be highly expensive and unstable due to the modernization of the developing countries. So the studies for a material cost should be continued to identify the actual cost of an HLW repository

  1. Functioning of blocks of compacted bentonite in a repository for spent nuclear fuels

    International Nuclear Information System (INIS)

    Boergesson, Lennart; Kalbantner, P.; Sjoeblom, R.

    2001-12-01

    The main purpose of the presented work is to provide The Swedish Nuclear Fuel and Waste Management Company (SKB) with a proposed set of requirements regarding the functioning of the blocks of compacted bentonite. These blocks are intended to constitute the bentonite envelope which after uptake of water will form the buffer between the canister and the rock. The purpose is also to provide a basis for SKB for their direction of the continued development work for the selection of a reference technology and for creating a quality system for the buffer material. No attempts are made in the report to derive the functional requirements. Instead, such requirements are postulated based on realistic scenarios regarding the chain of processes from excavation - transport - preparation of press powder - compaction - handling and emplacement in the deposition hole. It is the strategy of SKB to use a natural material which after the above-mentioned processes forms a buffer with properties which closely resemble those of the original material. This implies that all process steps must be designed in such a way that the properties of the bentonite do not change to any significant degree with respect to the disposal function. The main results in the report are as follows: A set of functional requirements are compiled and presented. These concord with the different descriptions given on the process steps. The requirements are generic and are assessed to be relatively invariant for various operational requirements and process controls. The process chain comprising excavation of bentonite - transport - preparation of press powder - compaction - handling and emplacement are explained. The presentations of functional requirements and processes are foreseen to constitute a basis for a comparison between uniaxial and isostatic compaction and can be an important basis for SKB's quality work. The development of cracks in the bentonite blocks has been identified as an important aspect for the

  2. Saturation of compacted bentonite under repository conditions: long-term experimental evidences

    International Nuclear Information System (INIS)

    Villar, M.V.; Martin, P.L.; Gomez-Espina, R.; Garcia-Sineriz, J.L.; Barcena, I.; Lloret, A.

    2010-01-01

    bentonite columns have been running for 7 years. In one of them hydration is taking place at room isothermal conditions. The water intake is higher for the sample tested at room temperature, because the hot zones of the sample tested under thermal gradient remain desiccated for long time. In fact, both tests seem to have reached a steady state, since the relative humidity inside the bentonite barely changes, what suggests that the process that causes the water intake to be so slow, must not be solely connected to the thermal gradient. Other tests performed in smaller samples under thermal gradient did show a final full saturation for tests durations around 30-40 days and homogenisation of water contents along the blocks for longer testing periods. Some conclusions could be drawn from these experimental observations: - The rate of hydration depends on the buffer and surrounding media permeabilities, waste temperature and buffer thickness. - It is not clear if full saturation can be reached for any combination of barrier thickness, thermal gradient and material permeability. - For predicting the long-term behaviour of the barrier, the numerical models must take into account the effect on bentonite permeability of the change in its microstructure upon hydration. - When the dry density of the barrier is high, the density of the adsorbed water would be higher than 1 g/ cm 3 , and more water than expected would fit in the bentonite pores. (authors)

  3. HM modelling of in-situ gas injection tests in bentonite and argillite: the PGZ experiment

    International Nuclear Information System (INIS)

    Gerard, P.; Charlier, R.; Radu, J.P.; La Vaissiere, R. de; Talandier, J.; Collin, F.

    2010-01-01

    Document available in extended abstract form only. During long-term repository of high and intermediate level nuclear waste in deep argillaceous geological formation, steel containers will corroded and organic material will be irradiated. The two processes lead mostly to hydrogen production. This study deals with the numerical modelling of the gas migration in both the host formation and a bentonite plug, with an emphasis on coupling between the gas transfer and the mechanical strains and stresses. More particularly the study aims to support the design of the PGZ in situ experiment that will be performed by Andra in its underground laboratory at Bure. The objective of the experiment is the analysis of the dynamics of the bentonite plug re-saturation, studying the competition between the liquid water coming from the argillite and a gas injection. The modelled experiment consists of a borehole drilled in rock clay, inside which a plug of MX-80 bentonite is set. The bentonite is naturally re-saturated by water coming from the host formation. At the same time a gas pressure, higher than the initial water pressure in the host rock, is imposed at both ends of the plug. The developed model takes into account the coupling between the mechanical behaviour and the water and gas transfers in undisturbed geo-materials. It manages explicitly liquid and vapour water, gaseous and dissolved hydrogen. Elastoplastic and non-linear elastic model are used to model the behaviour of, respectively, the argillaceous rock and the bentonite. The numerical results show the small desaturation obtained in bentonite and argillite. The influence of the coupling of the mechanic on the water and gas transfers is thus limited (due to the Bishop's effective stress). The swelling of the bentonite plug is not hindered by the gas migration and the confining effect of the engineered barrier is maintained. An analysis is made of the influence of the main transfer rock properties on the gas pressure

  4. Fe-bentonite. Experiments and modelling of the interactions of bentonites with iron

    Energy Technology Data Exchange (ETDEWEB)

    Herbert, Horst-Juergen; Xie, Mingliang [Gesellschaft fuer Anlagen- und Reaktorsicherheit mbH (GRS), Koeln (Germany); Kasbohm, Joern; Lan, Nguyen T. [Greifswald Univ. (Germany); Hoang Thi Minh Thao [Hanoi Univ. of Science (Viet Nam)

    2011-11-15

    The main objectives of this study were to enhance the understanding of the interactions of bentonites with steel containers in the near field of a repository in salt formations and to determine missing experimental thermo-hydraulical-chemical and mineralogical data needed for the THC modelling of the interactions of bentonites with iron. At the beginning of this project a literature review helped to clarify the state of the art regarding the above mentioned objectives prior to the start of the experimental work. In the following experimental programme the hydraulic changes in the pore space of compacted MX80 bentonites containing metallic iron powder and in contact with three solutions of different ionic strength containing different concentrations of Fe{sup 2+} have been investigated. The alterations of MX80 and several other bentonites have been assessed in contact with the low ionic strength Opalinus Clay Pore Water (OCPW) and the saturated salt solutions NaCl solution and IP21 solution. Under repository relevant boundary conditions we determined on compacted MX80 samples with the raw density of 1.6 g/cm{sup 3} simultaneously interdependent properties like swelling pressures, hydraulic parameters (permeabilities and porosities), mineralogical data (changes of the smectite composition and iron corrosion products), transport parameters (diffusion coefficients) and thermal data (temperature dependent reaction progresses). The information and data resulting from the experiments have been used in geochemical modelling calculations and the existing possibilities and limitations to simulate these very complex near field processes were demonstrated. The main conclusion of this study is that the alteration of bentonites in contact with iron is accentuated and accelerated. Alterations in contact with solutions of different ionic strength identified by the authors in previous studies were found be much more intensive in contact with metallic iron and at elevated

  5. Impact of granular drops

    KAUST Repository

    Marston, J. O.

    2013-07-15

    We investigate the spreading and splashing of granular drops during impact with a solid target. The granular drops are formed from roughly spherical balls of sand mixed with water, which is used as a binder to hold the ball together during free-fall. We measure the instantaneous spread diameter for different impact speeds and find that the normalized spread diameter d/D grows as (tV/D)1/2. The speeds of the grains ejected during the “splash” are measured and they rarely exceed twice that of the impact speed.

  6. Impact of granular drops

    KAUST Repository

    Marston, J. O.; Mansoor, Mohammad M.; Thoroddsen, Sigurdur T

    2013-01-01

    We investigate the spreading and splashing of granular drops during impact with a solid target. The granular drops are formed from roughly spherical balls of sand mixed with water, which is used as a binder to hold the ball together during free-fall. We measure the instantaneous spread diameter for different impact speeds and find that the normalized spread diameter d/D grows as (tV/D)1/2. The speeds of the grains ejected during the “splash” are measured and they rarely exceed twice that of the impact speed.

  7. Dustiness behaviour of loose and compacted Bentonite and organoclay powders: What is the difference in exposure risk?

    International Nuclear Information System (INIS)

    Jensen, Keld Alstrup; Koponen, Ismo Kalevi; Clausen, Per Axel; Schneider, Thomas

    2009-01-01

    Single-drop and rotating drum dustiness testing was used to investigate the dustiness of loose and compacted montmorillonite (Bentonite) and an organoclay (Nanofil 5), which had been modified from montmorillonite-rich Bentonite. The dustiness was analysed based on filter measurements as well as particle size distributions, the particle generation rate, and the total number of generated particles. Particle monitoring was completed using a TSI Fast Mobility Particle Sizer (FMPS) and a TSI Aerosol Particle Sizer (APS) at 1 s resolution. Low-pressure uniaxial powder compaction of the starting materials showed a logarithmic compaction curve and samples subjected to 3.5 kg/cm 2 were used for dustiness testing to evaluate the role of powder compaction, which could occur in powders from large shipments or high-volume storage facilities. The dustiness tests showed intermediate dustiness indices (1,077-2,077 mg/kg powder) in tests of Nanofil 5, Bentonite, and compacted Bentonite, while a high-level dustiness index was found for compacted Nanofil 5 (3,487 mg/kg powder). All powders produced multimodal particle size-distributions in the dust cloud with one mode around 300 nm (Bentonite) or 400 nm (Nanofil 5) as well as one (Nanofil 5) or two modes (Bentonite) with peaks between 1 and 2.5 μm. The dust release was found to occur either as a burst (loose Bentonite and Nanofil 5), constant rate (compacted Nanofil 5), or slowly increasing rate (compacted Bentonite). In rotating drum experiments, the number of particles generated in the FMPS and APS size-ranges were in general agreement with the mass-based dustiness index, but the same order was not observed in the single-drop tests. Compaction of Bentonite reduced the number of generated particles with app. 70 and 40% during single-drop and rotating drum dustiness tests, respectively. Compaction of Nanofil 5 reduced the dustiness in the single-drop test, but it was more than doubled in the rotating drum test. Physically relevant

  8. Natural analogue studies of bentonite reaction under hyperalkaline conditions. Overview of ongoing work at the Zambales ophiolite, Philippines

    International Nuclear Information System (INIS)

    Fujii, N.; Yanakawa, M.; Arcilla, C.A.; Pascua, C.; Namiki, K.; Sato, T.; Shikazono, N.; Alexander, W.R.

    2011-01-01

    Bentonite is one of the safety-critical components of the engineered barrier system for the disposal concepts developed for many types of radioactive waste. However, bentonite - especially the swelling clay component that contributes to its essential barrier functions - is unstable at high pH. To date, results from laboratory tests on bentonite degradation have been ambiguous as the reaction rates are so slow as to be difficult to observe. As such, a key goal in this project is to examine the reaction of natural bentonites in contact with natural hyperalkaline groundwaters to determine if any long-term alteration of the bentonite occurs. Ophiolites have been identified as sources of hyperalkaline groundwaters that can be considered natural analogues of the leachates produced by some cementitious materials in repositories for radioactive waste. At the Zambales ophiolite in the Philippines, widespread active serpentinisation results in hyperalkaline groundwaters with measured pH values of up to 11.7, falling into the range typical of low-alkali cement porewaters. These cements are presently being developed worldwide to minimise the geochemical perturbations which are expected to result from the use of OPC-based concretes (see Kamei et al., this conference, for details). In particular, it is hoped that the lower pH of the low-alkali cement leachates will reduce, or even avoid entirely, the potential degradation of the bentonite buffer which is expected at the higher pH levels (12.5 and above) common to OPC-based concretes. During recent field campaigns at two sites in the Zambales ophiolite (Mangatarem and Bigbiga), samples of bentonite and the associated hyperalkaline groundwaters have been collected by drilling and trenching. At Mangatarem, qualitative data from a 'fossil' (i.e. no groundwater is currently present) reaction zone indicates some alteration of the bentonite to zeolite, serpentine and CSH phases. Preliminary reaction path modelling suggests that the

  9. Prediction of pressure of bentonite buffer in model test of disposal pit for high-level radioactive waste

    International Nuclear Information System (INIS)

    Komine, Hideo; Osada, Toru; Takao, Hajime; Ueda, Hiroyoshi

    2013-01-01

    Bentonite-based buffer materials for high-level radioactive waste (HLW) disposal are expected to fill up the space between buffer and a wall of the disposal pit, and/or between buffer and an waste-container called as overpack by its swelling deformation. That is called as self-sealing ability. This study performs the model tests simulated the relationship between buffer and space mentioned above. It also investigates the validity of the theoretical equations for evaluating the swelling characteristics of bentonite-based buffer and backfill material, which were proposed in Komine and Ogata (2003, 2004), by comparing the calculations and the experimental results. (author)

  10. Wave propagation of spectral energy content in a granular chain

    NARCIS (Netherlands)

    Shrivastava, Rohit Kumar; Luding, Stefan

    2017-01-01

    A mechanical wave is propagation of vibration with transfer of energy and momentum. Understanding the spectral energy characteristics of a propagating wave through disordered granular media can assist in understanding the overall properties of wave propagation through inhomogeneous materials like

  11. Mechanical Behavior of Granular/Particulate Media Reinforced with Fibers

    National Research Council Canada - National Science Library

    Michalowski, Radoslw

    1999-01-01

    ... out. This investigation was built on the results of a previous study. Fiber-reinforced granular material was considered as a composite, and a mathematical homogenization scheme was used to arrive at its macroscopic properties...

  12. Characterization of LDPE/PBAT/PLA and organophilic bentonite nanocomposites

    International Nuclear Information System (INIS)

    Figueredo, Daniela Casimiro de; Viana, Hamilton; Rosa, Derval dos Santos; Poveda, Patricia Negrini Siqueira

    2011-01-01

    Due to the ascension of Green chemistry in the 90's, it has been a demand for the production of biodegradable materials which cause minimal impacts to environment. Some nanocomposites are in this material class. In this context, six formulations containing low density polyethylene (LDPE), a compatibilized commercial poly(butylene adipate-co-terephthalate) (PBAT) and poly(lactic acid) (PLA) blend under the trademark Ecovio and organophilic bentonite were processed by extrusion to make films which were characterized by X-ray diffraction, melt flow index (MFI) and mechanical tests. X- ray pattern revealed that the nano clay was composed predominantly of montmorillonite, quartz and kaolinite and it could promote formation of intercalated or exfoliated composites. Nano clay also affected the fluidity of composites with variations in module up to 4%, as evidenced by melt flow index. Mechanical tests demonstrated that there was no uniformity in mechanical behavior of the nanocomposites. (author)

  13. Bentonite engineered barrier building method for radioactive waste on sub-surface disposal test project

    International Nuclear Information System (INIS)

    Mori, Takuo; Takahashi, Shinichi; Takeuchi, Kunifumi; Namiki, Kazuto

    2008-01-01

    The engineering barriers such as clay and concrete materials are planned to use for covering radioactive waste in cavern-type disposal facility. The requirement to clay barrier is very low permeability, which could be satisfied by high density Bentonite, and such a compaction method will be needed. Two methods, compaction and air shot, were tested in engineering scale for constructing a high-density clay barrier. Two types of compaction equipments, 'Teasel plate' and 'Plate compacter', were developed and engineering scale experiments were performed for compacting Bentonite only and Bentonite-sand-aggregate mixture. As a result, the Teasel plate can reach higher density Bentonite in relatively short time in comparison to other equipments. While, regarding air shot method, an air-shot machine in a tunnel construction site was tested by different water adding methods (wet, dry, and half wet). It is concluded that the dry and half wet constructing methods will achieve reasonable workability. As a result, the best construction option can be chosen according to the locations of radioactive waste facility. (author)

  14. In situ reactive compatibilization of natural rubber/acrylic-bentonite composites via peroxide-induced vulcanization

    International Nuclear Information System (INIS)

    Fu, Lihua; Lei, Zhiwen; Xu, Chuanhui; Chen, Yukun

    2016-01-01

    To achieve good interfacial interaction between fillers and rubber matrix is always a hot topic in rubber reinforcing industry. In this paper, acid activated bentonite (Bt) was alkalified to be alkaline calcium-bentonite (ACBt), then acrylic acid (AA) was employed to modify ACBt to obtain acrylic-bentonite (ABt). The results of Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) illustrated that acrylate groups were chemically boned onto the surface of Bt and the layer spacing of Bt was increased. During peroxide-induced vulcanization, in situ compatibilization of ABt was realized via the reaction between the unsaturated bonds of acrylate groups on the surface of Bt and the natural rubber (NR) chains. This resulted in an enhanced cross-linked network which contributed to the improved mechanical properties of NR/ABt composites. - Highlights: • Acrylate groups were chemically boned onto the surface of bentonite. • In situ compatibilization was realized via the reaction of acrylate group and NR. • ABt particles participated in forming the NR crosslink network. • A potential reinforcing material options for “white” rubber products.

  15. In situ reactive compatibilization of natural rubber/acrylic-bentonite composites via peroxide-induced vulcanization

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Lihua; Lei, Zhiwen [Guangxi Key Laboratory of Petrochemical Resource Processing and Process Intensification Technology, School of Chemistry and Chemical Engineering, Guangxi University, Nanning 530004 (China); Xu, Chuanhui, E-mail: xuhuiyee@gxu.edu.cn [Guangxi Key Laboratory of Petrochemical Resource Processing and Process Intensification Technology, School of Chemistry and Chemical Engineering, Guangxi University, Nanning 530004 (China); Chen, Yukun, E-mail: cyk@scut.edu.cn [The Key Laboratory of Polymer Processing Engineering, Ministry of Education, China(South China University of Technology), Guangzhou, 510640 (China)

    2016-02-15

    To achieve good interfacial interaction between fillers and rubber matrix is always a hot topic in rubber reinforcing industry. In this paper, acid activated bentonite (Bt) was alkalified to be alkaline calcium-bentonite (ACBt), then acrylic acid (AA) was employed to modify ACBt to obtain acrylic-bentonite (ABt). The results of Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) illustrated that acrylate groups were chemically boned onto the surface of Bt and the layer spacing of Bt was increased. During peroxide-induced vulcanization, in situ compatibilization of ABt was realized via the reaction between the unsaturated bonds of acrylate groups on the surface of Bt and the natural rubber (NR) chains. This resulted in an enhanced cross-linked network which contributed to the improved mechanical properties of NR/ABt composites. - Highlights: • Acrylate groups were chemically boned onto the surface of bentonite. • In situ compatibilization was realized via the reaction of acrylate group and NR. • ABt particles participated in forming the NR crosslink network. • A potential reinforcing material options for “white” rubber products.

  16. Evaluation of hydraulic conductivities of bentonite and rock under hyper alkaline and nitrate conditions (3)

    International Nuclear Information System (INIS)

    Iriya, Keishiro; Kubo, Hiroshi

    2004-02-01

    Circumstance of TRU waste repository shows alkaline condition due to leaching of cementitious materials. The waste containing significant soluble nitrate may changes ground water chemistry to high ion strength. Consolidation test and permeability test are carried out in order to assess quantitatively permeability of bentonite altered by hyper alkaline and nitrate. Modeling is progressed based on experimental results. The following results are obtained. 1) Consolidation test was carried out in 3 types of bentonite and 30 % sand mixture in which cation exchanged with nitrate. It is noted that permeability of bentonite increased at from 40 to 200 times by cation exchange. 2) Permeability of hyper alkaline solution is almost same to water. Permeability of hyper alkaline solution with nitrates increased corresponding to rising ion strength. 3) The results of batch of column test were simulated. The model can explain clearly the results in short period. This can estimate leaching ratio and secondary minerals. The model can simulate the experimental results by two types of velocity theory on altering bentonite. (author)

  17. Geotechnical characteristics of bentonite/sandy silt mixes for use in waste disposal sites

    International Nuclear Information System (INIS)

    Abeele, W.V.

    1984-06-01

    The coefficient of consolidation for bentonite/sandy silt ratios of 0.04 to 0.14 decreases inversely proportional with the square of that ratio, whereas the compression index, the swelling index, and the permeability change index increase with increasing bentonite ratio. A strong relationship also exists between the void ratio and the logarithm of the applied stress for any given bentonite ratio. The empirical linear relationship between the void ratio and the logarithm of the applied stress, developed by Taylor, is excellent and enables us to limit the evaluation of conductivity at any void ratio to the measurement of the initial and the desired void ratio, the initial conductivity, and the permeability change index. This allows us to read directly, for a given bentonite ratio, the void ratio (or compaction) needed so that a required hydraulic conductivity will prevail. This is crucial in the choice of materials or mixes to be used in a wick system where an established differentiation in hydraulic conductivity is desirable

  18. Strength characteristics of lightly solidified dredged marine clay admixed with bentonite

    Science.gov (United States)

    Ariffin, Syazwana Tajul; Chan, Chee-Ming

    2017-11-01

    Strength characteristic is a significant parameter in measuring the effect of soil improvement and effective composition of solidification. In this study, the dredged marine sediment (DMS) collected from Kuala Perlis (Malaysia) was examined to determine its strength characteristics under light cement solidification with bentonite. Dredged marine clay generally has the low shear strength and high void ratio, and consists mainly of soil particles of the fine-grained type. As a discarded geo-waste, it can be potentially treated to for reuse as a backfill material instead of being disposed of, hence reducing the negative impact on the environment. Physico-chemical parameters of the dredged sample were first determined, then solidification was carried out to improve the engineering properties by admixing ordinary Portland cement (OPC) as the binder and bentonite as a volume enhancer to the soil. The DMS was treated with the addition of 3 % and 6 % cement and bentonite within the range of 0-30 %. The specimens were cured at room temperature for 3, 7 and 14 days. The strength gain was measured by unconfined compression test and vane shear test. The laboratory test results were analyzed to establish the relationship between strength properties and solidification specifications. In summary, the strength of specimens increased with the increase of the quantity of bentonite and cement to get the effective composition of the specimen.

  19. Evaluation of hydraulic conductivities of bentonite and rock under hyper alkaline and nitrate conditions. 2

    International Nuclear Information System (INIS)

    Iriya, Keishiro; Fujii, Kensuke; Kubo, Hiroshi

    2003-02-01

    Circumstance of TRU waste repository shows alkaline condition due to leaching of cementitious materials. The waste containing significant soluble nitrate may changes ground water chemistry to high ion strength. Several experimental studies have been carried out in this study in order to assess quantitatively water conductivity of bentonite which is altered by hyper alkaline and nitrate. Modeling for previous results is carried out and several requirements to be defined are proposed. The conclusion of this study is summarized as below. Secondary minerals of bentonite alteration due to hyper alkaline with nitrate: 1) CSH and CAH were observed corresponding to solving montmorillonite in AWN solution. 2) Na 2 O Al 2 O 3 1.68SiO 2 generated from 90 days in batch experiment and it was observed in 360 days. Assessment of swelling and water conductivity changing by hyper alkaline with nitrate: 1) Little changing of water conductivity of bentonite was observed by saturated Ca(OH) 2 solution and hyper alkaline solution. The conductivity significantly increased by penetrating sodium nitrate solution. 2) Water conductivity of ion exchanged bentonite by hyper alkaline solution significantly increased. It increased more by penetrating AWN solution. Modeling of tuff alteration by hyper alkaline solution: 1) Flow through test is proposed since soluble velocity to hyper alkaline solution should be defined. (author)

  20. Study on GMZ bentonite-sand mixture by undrained triaxial tests

    Directory of Open Access Journals (Sweden)

    Sun Wen-jing

    2016-01-01

    Full Text Available It is particularly necessary to study the deformation, strength and the changes of pore water pressure of bentonite-based buffer/backfill materials under the undrained condition. A series of isotropic compression tests and triaxial shear tests under undrained conditions were conducted on the compacted saturated/unsaturated GMZ bentonite-sand mixtures with dry mass ratio of bentonite/sand of 30:70. During the tests, the images of the sample were collected by photographic equipment and subsequently were cropped, binarized and centroids marked by image processing technique. Based on identification of the variation of the position of marked centroids, the deformation of the sample can be determined automatically in real-time. Finally, the hydro-mechanical behaviour of saturated and unsaturated bentonite-sand mixtures under the undrained condition can be obtained. From results of triaxial shear tests on unsaturated samples under constant water content, inflated volumetric deformation transforms to contractive volumetric deformation due to the increase of the confining pressure and lateral expansion deformation are observed due to the increase in the shearing stress. Moreover, the net mean stress affects the initial stiffness, undrained shear strength and deformation of the sample during the undrained shear tests.

  1. Chemical and mineralogical aspects of water-bentonite interaction in nuclear fuel disposal conditions

    International Nuclear Information System (INIS)

    Melamed, A.; Pitkaenen, P.

    1996-01-01

    In the field of nuclear fuel disposal, bentonite has been selected as the principal sealing and buffer material for placement around waste canisters, forming both a mechanical and chemical barrier between the radioactive waste and the surrounding ground water. Ion exchange and mineral alteration processes were investigated in a laboratory study of the long-term interaction between compacted Na-bentonite (Volclay MX-80) and ground water solutions, conducted under simulated nuclear fuel disposal conditions. The possible alteration of montmorillonite into illite has been a major object of the mineralogical study. However, no analytical evidence was found, that would indicate the formation of this non-expandable clay type. Apparently, the change of montmorillonite from Na- to Ca-rich was found to be the major alteration process in bentonite. In the water, a concentration decrease in Ca, Mg, and K, and an increase in Na, HCO 3 and SO 4 were recorded. The amount of calcium ions available in the water was considered insufficient to account for the recorded formation of Ca-montmorillonite. It is therefore assumed that the accessory Ca-bearing minerals in bentonite provide the fundamental source of these cations, which exchange with sodium during the alteration process. (38 refs.)

  2. Bentonite as backfill in a final repository for high-level waste: chemical aspects

    International Nuclear Information System (INIS)

    Grauer, R.

    1986-01-01

    The present Nagra concept for disposal of high-level waste foresees emplacing the steel containers enclosing the borosilicate glass in tunnels at a depth of 1000 to 1500 m. These tunnels are to be backfilled with bentonite. Bentonites are suitable as a backfill due to their swelling capability, their low hydraulic conductivity and their sorption properties. This report is restricted to chemical aspects of the backfill material: swelling capability, sorption properties and long-term stability. Under repository conditions, the swelling of monmorillonite upon water inflow is primarily innercrystalline. Cation adsorption, which is important for nuclide retention in the repository, can be described by appropriate models. It can be concluded from natural analogue studies and from laboratory experiments that the properties of the backfill material will not alter significantly over a periode of 10/sup 6/ years. Nevertheless in the long term, the formulation of mixed-layer illite/monmorillonite cannot be ruled out. Such mixed-layer clays still have good swelling and sorption properties. Given the quantity ratios foreseen, no adverse changes due to radioactive decay are to be expected. The interaction between the bentonite and the container corrosion products must, in the absence of literature data, be investigated experimentally. The type of reaction products expected (iron-containing clay minerals) and the high bentonite/iron ratio lead to the conclusion that the function of the backfill need not be impaired by these processes. Because of its better stability, a calcium bentonite is preferable to the sodium variant. A low iron content is desirable because, under reducing conditions, the surface charge of the montorillonite is increased by reduction of iron(III). Organic and sulphidic contaminants should also be kept to a minimum

  3. Preparation and Characterization of Dabco (1,4-Diazabicyclo [2.2.2]octane) modified bentonite: Application for Congo red removal

    Science.gov (United States)

    Taher, Tarmizi; Rohendi, Dedi; Mohadi, Risfidian; Lesbani, Aldes

    2018-01-01

    Natural bentonite provided from Sarolangun deposit was modified with 1,4-Diazabicyclo[2.2.2]octane (Dabco) to form a new class of porous material. Prior further modification, the natural bentonite was cleaned up and activated by NaCl to remove the impurities and increase the bentonite nature. Dabco modified bentonite (Dabco-bent) was prepared by exchanging the inorganic cation placed in the interlayer space of the montmorillonite mineral structure with the 0.01 M Dabco1+ at pH 6. The modified bentonite products were characterized using X-Ray powder diffraction and FT-IR to monitor the change of the bentonite crystallinity and function group due to the modification process. The XRD result confirmed that during the modification process, the d(001) of smectite peak at 2q around 6° was shifted. After the modification, the d(001) reflection of the montmorillonite interlayer was shifted 0.36° to the left indicating that the interlayer space of the montmorillonite has been expanded during the modification process. The FTIR spectra of Dabco modified bentonite exhibit no significantly different with the host bentonite. However, the presence of the new band at the wavenumber around 3000 and 2800 cm-1 indicates that the Dabco molecule has been successfully inserted to the bentonite molecule. The Congo red adsorption experiment was performed onto Dabco-bent product by batch technique. The experiment data described that kinetic model for Congo red adsorption onto Dabco-bent was adequately followed the second-order kinetic model and well described by Freundlich adsorption isotherm model.

  4. Physicochemical and Geotechnical Alterations to MX-80 Bentonite at the Waste Canister Interface in an Engineered Barrier System

    Directory of Open Access Journals (Sweden)

    Christopher W. Davies

    2017-08-01

    Full Text Available The study investigated the basic geomechanical and mineralogical evolution of the bentonite barrier under various experimental boundary conditions which replicated the near-field Thermo-Hydro-Chemico (THC conditions in a repository. The relationships between the physicochemical alterations and changes in the geotechnical properties have seldom been studied, especially on a consistent dataset. This paper attempts to link the physicochemical properties of Na-bentonite (MX-80 to the macro-scale engineering functionality of the bentonite post THC exposure. Experiments investigated the impact of THC variables on the engineering and physicochemical functionality of the bentonite with respect to its application within a High-Level Waste (HLW engineered barrier system. Intrinsic alterations to the MX-80 bentonite under relatively short-term exposure to hydrothermal and chemical conditions were measured. Additionally, two long-term tests were conducted under ambient conditions to consider the impact of exposure duration. The intrinsic measurements were then related to the overall performance of the bentonite as a candidate barrier material for application in a UK geological disposal facility. Findings indicate that exposure to thermo-saline-corrosion conditions (i.e., corrosion products derived from structural grade 275 carbon steel inhibits the free swell capacity and plasticity of the bentonite. However, the measured values remained above the design limits set out for the Swedish multi-barrier concept, from which the UK concept may take a lead. Corrosion alone does not appear to significantly affect the geotechnical measurements compared with the influence of thermal loading and high saline pore water after relatively short-term exposure. Thermal and corrosion exposure displayed no impact on the intrinsic swelling of the smectite component, indicating that no significant structural alteration had occurred. However, when exploring more complex saline

  5. Research program to study the gamma radiation effects in Spanish bentonites; Programa de investigacion para estudiar los efectos de la radiacion gamma en bentonitas calcicas espanolas

    Energy Technology Data Exchange (ETDEWEB)

    Dies, J; Tarrasa, F [Universidad Politecnica de Catalunya (Spain); Cuevas de las, C; Miralles, L; Pueyo, J J [Universidad de Barcelona (Spain)

    2000-07-01

    The engineering barrier of a radioactive waste underground disposal facility, placed in a granitic host rock, will consist of a backfill of compacted bentonite blocks. At first, this material will be subjected to a gamma radiation field, from the waste canister, and heat from the spent fuel inside the canister. Moreover, any groundwater that reaches the repository will saturate the bentonite. For these reasons the performance of the engineered barrier must be carefully assessed in laboratory experiments. (Author)

  6. Backfilling of deposition tunnels: Use of bentonite pellets

    International Nuclear Information System (INIS)

    Dixon, David; Sanden, Torbjoern; Jonsson, Esther; Hansen, Johanna

    2011-02-01

    The state of knowledge related to use of bentonite pellets as part of backfill or other gap filling components in repository applications is reviewed. How the pellets interact with adjacent sealing materials and the surrounding rock mass is a critical aspect in determining backfill behaviour. The key features and processes that determine how the pellet component of the KBS-3V deposition tunnel backfill will behave are discussed and recommendations related to what additional information needs to be developed are provided. Experiences related to pellet material composition, size, shape, placement options and more importantly, the density to which they can be placed all indicate that there are significant limitations to the achievable as-placed density of bentonite pellet fill. Low as-placed density of the pellet fill component of the backfill is potentially problematic as the outermost regions of tunnel backfill will be the first region of the backfill to be contacted by water entering the tunnels. It is also through this region that initial water movement along the length of the deposition tunnels will occur. This will greatly influence the operations in a tunnel, especially with respect to situations where water is exiting the downstream face of still open deposition tunnels. Pellet-filled regions are also sensitive to groundwater salinity, susceptible to development of piping features and subsequent mechanical erosion by through flowing water, particularly in the period preceding deposition tunnel closure. A review of the experiences of various organisations considering use of bentonite-pellet materials as part of buffer or backfill barriers is provided in this document. From this information, potential options and limitations to use of pellets or pellet-granule mixtures in backfill are identified. Of particular importance is identification of the apparent upper-limits of dry density to which such materials can to be placed in the field. These bounds will

  7. Backfilling of deposition tunnels: Use of bentonite pellets

    Energy Technology Data Exchange (ETDEWEB)

    Dixon, David (Atomic Energy of Canada Limited (Canada)); Sanden, Torbjoern (Clay Technology AB (Sweden)); Jonsson, Esther (Swedish Nuclear Fuel and Waste Mangaement Co. (Sweden)); Hansen, Johanna (Posiva Oy (Finland))

    2011-02-15

    The state of knowledge related to use of bentonite pellets as part of backfill or other gap filling components in repository applications is reviewed. How the pellets interact with adjacent sealing materials and the surrounding rock mass is a critical aspect in determining backfill behaviour. The key features and processes that determine how the pellet component of the KBS-3V deposition tunnel backfill will behave are discussed and recommendations related to what additional information needs to be developed are provided. Experiences related to pellet material composition, size, shape, placement options and more importantly, the density to which they can be placed all indicate that there are significant limitations to the achievable as-placed density of bentonite pellet fill. Low as-placed density of the pellet fill component of the backfill is potentially problematic as the outermost regions of tunnel backfill will be the first region of the backfill to be contacted by water entering the tunnels. It is also through this region that initial water movement along the length of the deposition tunnels will occur. This will greatly influence the operations in a tunnel, especially with respect to situations where water is exiting the downstream face of still open deposition tunnels. Pellet-filled regions are also sensitive to groundwater salinity, susceptible to development of piping features and subsequent mechanical erosion by through flowing water, particularly in the period preceding deposition tunnel closure. A review of the experiences of various organisations considering use of bentonite-pellet materials as part of buffer or backfill barriers is provided in this document. From this information, potential options and limitations to use of pellets or pellet-granule mixtures in backfill are identified. Of particular importance is identification of the apparent upper-limits of dry density to which such materials can to be placed in the field. These bounds will

  8. STUDY OF THERMAL AND ACID STABILITY OF BENTONITE CLAY

    Directory of Open Access Journals (Sweden)

    Karna Wijaya

    2010-06-01

    Full Text Available The thermal and acid stability of the bentonite clays (Na- and Ca-bentonite have been tested. The thermal stability testing has been carried out by heating 5 gram of the clays  for five hours at 200, 300 and 500 °C respectively, meanwhile acid stability testing was performed by immersing 5 gram clays into 100 mL sulphuric acid 1M, 2M and 3M for 24 hours. The tested clays, then were characterized by means of X-Ray difractometry and IR-spectroscopy methods. The characterization results showed that upon heating, both Ca- and Na-bentonites