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Sample records for granular bentonite material

  1. 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

  2. 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)

  3. 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.)

  4. 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

  5. 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

  6. Influence of seawater on swelling characteristics of bentonite buffer material

    International Nuclear Information System (INIS)

    Naoi, Yutaka; Komine, Hideo; Yasuhara, Kazuya; Murakami, Satoshi; Momose, Kazuo; Sakagami, Takeharu

    2005-01-01

    A high level radioactive waste disposal facility may be built on a coastal area. Therefore, it is important to investigate the influence of seawater on bentonite buffer material. The purpose of this study is to investigate the influence of seawater on the swelling pressure and swelling deformation characteristics of five typical kinds of bentonites. This experimental work clarified the relations between the influence grade of seawater and compaction density, type of exchangeable-cation, montmorillonite content of the bentonite, and vertical pressure condition. Based on experimental results, a specification for the buffer material which can overcome the influence of seawater was defined. (author)

  7. 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

  8. 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.

  9. 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

  10. Acoustical properties of double porosity granular materials.

    Science.gov (United States)

    Venegas, Rodolfo; Umnova, Olga

    2011-11-01

    Granular materials have been conventionally used for acoustic treatment due to their sound absorptive and sound insulating properties. An emerging field is the study of the acoustical properties of multiscale porous materials. An example of these is a granular material in which the particles are porous. In this paper, analytical and hybrid analytical-numerical models describing the acoustical properties of these materials are introduced. Image processing techniques have been employed to estimate characteristic dimensions of the materials. The model predictions are compared with measurements on expanded perlite and activated carbon showing satisfactory agreement. It is concluded that a double porosity granular material exhibits greater low-frequency sound absorption at reduced weight compared to a solid-grain granular material with similar mesoscopic characteristics.

  11. 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

  12. Mechanics of Granular Materials (MGM)

    Science.gov (United States)

    2000-01-01

    The packing of particles can change radically during cyclic loading such as in an earthquake or when shaking a container to compact a powder. A large hole (1) is maintained by the particles sticking to each other. A small, counterclockwise strain (2) collapses the hole, and another large strain (3) forms more new holes which collapse when the strain reverses (4). Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. MGM experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditions that carnot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. (after T.L. Youd, Packing Changes and Liquefaction Susceptibility, Journal of the Geotechnical Engieering Division, 103: GT8,918-922, 1977)(Credit: NASA/Marshall Space Flight Center.)(Credit: University of Colorado at Boulder).

  13. 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

    2017-11-16

    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

  14. 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

  15. Passive Separation of Granular Materials

    Science.gov (United States)

    McCarthy, Joseph; Lievano, Diana

    2013-11-01

    Despite its industrial importance, particle separation techniques remain typically quite ``low tech'' and often are energy-intensive (e.g., sieving) or environmentally unfriendly (e.g., froth floatation) or both. Rate-based separation processes, on the other hand, represent a unique approach to particle separation that has the potential to be more flexible, more efficient, and more environmentally friendly than existing ``low tech'' techniques. In the present paper, we highlight a passive granular separation technique, where particles of differing properties flow through a device often called a Galton board. In this type of device, the gravity-driven flow of particles down an inclined plane causes collisions between the particles and distributed pegs along the board. Collisions between particles as well as between particles and pegs results in a diffusion-like motion of particles perpendicular to the flow. The extent of separation (i.e., how far one type of particle is removed from another) depends on the different distances traversed by the two types of particles and, ultimately, on the collision rate and energy dissipation for particle-peg events. A simple theory, based on statistics and single-collision mechanics, will be set forth for comparison with our results.

  16. 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.

  17. Investigation on hydraulic properties of compacted GMZ bentonite used as buffer/backfill material

    OpenAIRE

    Ye W. M.; Xin Q.; Chen B.; Chen Y.G.; Cui Y. J.

    2016-01-01

    During the past decades, GMZ bentonite has been widely investigated for its use as buffer/backfill materials in China. Based on a comprehensive review of the former studies, achievements on experimental and theoretic works on the hydraulic aspects of compacted GMZ bentonite with consideration of temperature effects are presented in this paper. Water retention property of compacted GMZ bentonite depends on constraint conditions. Temperature effects on water-retention depend on constraint condi...

  18. 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

  19. 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)

  20. Mechanics of Granular Materials (MGM) Cell

    Science.gov (United States)

    1996-01-01

    One of three Mechanics of Granular Materials (MGM) test cells after flight on STS-79 and before impregnation with resin. Note that the sand column has bulged in the middle, and that the top of the column is several inches lower than the top of the plastic enclosure. Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. Mechanics of Granular Materials (MGM) experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditons that carnot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. Credit: University of Colorado at Boulder

  1. Mechanics of Granular Materials Test Cell

    Science.gov (United States)

    1998-01-01

    A test cell for Mechanics of Granular Materials (MGM) experiment is shown from all three sides by its video camera during STS-89. Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. Mechanics of Granular Materials (MGM) experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditons that carnot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. Credit: NASA/Marshall Space Flight Center (MSFC)

  2. Mechanics of Granular Materials (MGM) Flight Hardware

    Science.gov (United States)

    1997-01-01

    A test cell for the Mechanics of Granular Materials (MGM) experiment is shown in its on-orbit configuration in Spacehab during preparations for STS-89. The twin locker to the left contains the hydraulic system to operate the experiment. Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. Mechanics of Granular Materials (MGM) experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditons that carnot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. Note: Because the image on the screen was muted in the original image, its brightness and contrast are boosted in this rendering to make the test cell more visible. Credit: NASA/Marshall Space Flight Center (MSFC)

  3. Mechanics of Granular Materials-3 (MGM-3)

    Science.gov (United States)

    Sture, Stein; Alshibi, Khalid; Guynes, Buddy (Technical Monitor)

    2002-01-01

    Scientists are going to space to understand how earthquakes and other forces disturb grains of soil and sand. They will examine how the particle arrangement and structure of soils, grains and powders are changed by external forces and gain knowledge about the strength, stiffness and volume changes properties of granular materials at low pressures. The Mechanics of Granular Materials (MGM) experiment uses the microgravity of orbit to test sand columns under conditions that cannot be obtained in experiments on Earth. Research can only go so far on Earth because gravity-induced stresses complicate the analysis and change loads too quickly for detailed analysis. This new knowledge will be applied to improving foundations for buildings, managing undeveloped land, and handling powdered and granular materials in chemical, agricultural, and other industries. NASA wants to understand the way soil behaves under different gravity levels so that crews can safely build habitats on Mars and the Moon. Future MGM experiments will benefit from extended tests aboard the International Space Station, including experiments under simulated lunar and Martian gravity in the science centrifuge.

  4. State variables in dense granular materials

    Science.gov (United States)

    Daniels, Karen

    2009-11-01

    Granular materials are integral to many parts of our daily lives, from the coffee beans that fuel our mornings to the coal that fuels our power plants. Two related aspects of their dynamics are particularly striking: their ability to exhibit both solid-like and liquid-like behavior, and the presence of highly heterogeneous force chains in which the magnitude of the local stress varies widely over short distances. These distinctive behaviors are connected to the fact that granular materials are always out of equilibrium: first, because they are typically both driven and dissipative, but also because they remain in metastable states even when they aren't being driven. I will present recent results from several experiments ranging from the theoretically-motivated (the equilibration of state variables within a non-equilibrium system) to the practical (particle-segregation by size). The results of these experiments elucidate the complex behaviors which underlay granular dynamics, and provide a reason to hope that statistical physics might hold the keys to explaining the observed phenomena.

  5. 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

  6. Ultrasonic compaction of granular geological materials.

    Science.gov (United States)

    Feeney, Andrew; Sikaneta, Sakalima; Harkness, Patrick; Lucas, Margaret

    2017-04-01

    It has been shown that the compaction of granular materials for applications such as pharmaceutical tableting and plastic moulding can be enhanced by ultrasonic vibration of the compaction die. Ultrasonic vibrations can reduce the compaction pressure and increase particle fusion, leading to higher strength products. In this paper, the potential benefits of ultrasonics in the compaction of geological granular materials in downhole applications are explored, to gain insight into the effects of ultrasonic vibrations on compaction of different materials commonly encountered in sub-sea drilling. Ultrasonic vibrations are applied, using a resonant 20kHz compactor, to the compaction of loose sand and drill waste cuttings derived from oolitic limestone, clean quartz sandstone, and slate-phyllite. For each material, a higher strain for a given compaction pressure was achieved, with higher sample density compared to that in the case of an absence of ultrasonics. The relationships between the operational parameters of ultrasonic vibration amplitude and true strain rate are explored and shown to be dependent on the physical characteristics of the compacting materials. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. 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.

  8. Flowability of granular materials with industrial applications: an experimental approach

    OpenAIRE

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

    2017-01-01

    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 ...

  9. Mechanics of Granular Materials labeled hardware

    Science.gov (United States)

    2000-01-01

    Mechanics of Granular Materials (MGM) flight hardware takes two twin double locker assemblies in the Space Shuttle middeck or the Spacehab module. Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. MGM experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditions that carnot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. (Credit: NASA/MSFC).

  10. Mechanics of Granular Materials (MGM) Investigators

    Science.gov (United States)

    2000-01-01

    Key persornel in the Mechanics of Granular Materials (MGM) experiment at the University of Colorado at Boulder include Tawnya Ferbiak (software engineer), Susan Batiste (research assistant), and Christina Winkler (graduate research assistant). Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. MGM experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditions that cannot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. (Credit: University of Colorado at Boulder).

  11. Mechanic of Granular Materials (MGM) Investigator

    Science.gov (United States)

    2000-01-01

    Key persornel in the Mechanics of Granular Materials (MGM) experiment are Mark Lankton (Program Manager at University Colorado at Boulder), Susan Batiste (research assistance, UCB), and Stein Sture (principal investigator). Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. MGM experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditions that cannot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. (Credit: University of Colorado at Boulder).

  12. Cohesive granular materials composed of nonconvex particles.

    Science.gov (United States)

    Saint-Cyr, Baptiste; Radjai, Farhang; Delenne, Jean-Yves; Sornay, Philippe

    2013-05-01

    The macroscopic cohesion of granular materials made up of sticky particles depends on the particle shapes. We address this issue by performing contact dynamics simulations of 2D packings of nonconvex aggregates. We find that the macroscopic cohesion is strongly dependent on the strain and stress inhomogeneities developing inside the material. The largest cohesion is obtained for nearly homogeneous deformation at the beginning of unconfined axial compression and it evolves linearly with nonconvexity. Interestingly, the aggregates in a sheared packing tend to form more contacts with fewer neighboring aggregates as the degree of nonconvexity increases. We also find that shearing leads either to an isotropic distribution of tensile contacts or to the same privileged direction as that of compressive contacts.

  13. Three-phase fracturing in granular material

    Science.gov (United States)

    Campbell, James; Sandnes, Bjornar

    2015-04-01

    There exist numerous geo-engineering scenarios involving the invasion of a gas into a water-saturated porous medium: in fracking, this may occur during the fracking process itself or during subsequent gas penetration into propant beds; the process is also at the heart of carbon dioxide sequestration. We use a bed of water-saturated glass beads confined within a Hele-Shaw cell as a model system to illuminate these processes. Depending on packing density, injection rate and other factors, air injected into this system may invade in a broad variety of patterns, including viscous fingering, capillary invasion, bubble formation and fracturing. Here we focus primarily on the latter case. Fracturing is observed when air is injected into a loosely packed bed of unconsolidated granular material. Our approach allows us to image the complete fracture pattern as it forms, and as such to study both the topographical properties of the resulting pattern (fracture density, braching frequency etc) and the dynamics of its growth. We present an overview of the fracturing phenomenon within the context of pattern formation in granular fluids as a whole. We discuss how fracturing arises from an interplay between frictional, capillary and viscous forces, and demonstrate the influence of various parameters on the result.

  14. Pressure-shear experiments on granular materials.

    Energy Technology Data Exchange (ETDEWEB)

    Reinhart, William Dodd (Sandia National Laboratories, Albuquerque, NM); Thornhill, Tom Finley, III (, Sandia National Laboratories, Albuquerque, NM); Vogler, Tracy John; Alexander, C. Scott (Sandia National Laboratories, Albuquerque, NM)

    2011-10-01

    Pressure-shear experiments were performed on granular tungsten carbide and sand using a newly-refurbished slotted barrel gun. The sample is a thin layer of the granular material sandwiched between driver and anvil plates that remain elastic. Because of the obliquity, impact generates both a longitudinal wave, which compresses the sample, and a shear wave that probes the strength of the sample. Laser velocity interferometry is employed to measure the velocity history of the free surface of the anvil. Since the driver and anvil remain elastic, analysis of the results is, in principal, straightforward. Experiments were performed at pressures up to nearly 2 GPa using titanium plates and at higher pressure using zirconium plates. Those done with the titanium plates produced values of shear stress of 0.1-0.2 GPa, with the value increasing with pressure. On the other hand, those experiments conducted with zirconia anvils display results that may be related to slipping at an interface and shear stresses mostly at 0.1 GPa or less. Recovered samples display much greater particle fracture than is observed in planar loading, suggesting that shearing is a very effective mechanism for comminution of the grains.

  15. 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...

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

    Directory of Open Access Journals (Sweden)

    Gilberg Dominik

    2017-01-01

    Full Text Available 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.

  17. 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.

  18. 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

  19. Investigation on chemical effects on GMZ bentonite used as buffer materials

    Directory of Open Access Journals (Sweden)

    Ye Wei-Min

    2016-01-01

    Full Text Available GMZ bentonite has been selected as a buffer/backfill material for the design of Chinese HLW repository due to its suitable properties. Investigations have been conducted on this material to have a better understanding of its engineering behavior. In this paper, a review of the studies on the chemical effects in GMZ bentonite is presented. The adsorption of radionuclides Ni(II, Cr(III and Eu(III etc. on GMZ bentonite is investigated and the influences of external chemical agents are assessed. Some modifications on GMZ bentonite have been implemented to improve its adsorption properties. In the meantime, the influences of NaOH solutions with variations in concentration and pH values on hydraulic conductivity, mechanical behavior and mineralogy of GMZ bentonite are investigated with consideration of temperature. Effects of salt solutions are also assessed in different studies using solutions of Na+ and Ca2+, which are the predominant cations in the groundwater of Beishan area. It is observed that both cations influence the buffering behavior of bentonite at a different degree. Further investigations should be done for better understanding the influences of coupling factors and time on the chemical behavior of material.

  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. Transport phenomena in granular materials: Experiments and simulations

    Energy Technology Data Exchange (ETDEWEB)

    Ialali, P.; Sarkomaa, P. [Department of Energy and Environmental Engineering, Lappeenranta University of Technology, Lappeenranta (Finland); Mo Li [School of Material Science and Engineering, Georgia Institute of Technology, Atlanta, GA (United States)

    2007-07-01

    Granular materials are found in nature and in the technology. Common examples are sand, sugar, snow, synthetic powders, cement and soil. They are collections of individual solid grains with hybrid bulk properties so that they display both solid-like and fluid-like behaviors under various circumstances. Grains are interacting through collisions or contacts either with each other or with confining walls. The transport of mass, momentum and kinetic energy (not thermal energy) has been studied in deforming granular materials both theoretically and experimentally. In static granular media (no deformation), the distribution of forces and contact stresses has attracted a great deal of scientists' attention. In this article, different aspects of transport phenomena in sheared granular media are introduced based on experimental and numerical simulation results obtained by other scientists and via our research. The transport of mass and momentum are basically needed to understand the mixing phenomenon in granular materials. Deformation of granular material (the relative motion of grains) is extremely heterogeneous unlike the ordinary fluids and solids. Also, the most highlighted difference between granular materials and other states of matter is associated with the ineffectiveness of grains thermal energy in building the mechanical and physical properties of granular materials. Instead, the fluctuation of grains kinetic energy plays the major role in controlling the mechanics of granular materials. Strange behaviors of granular materials such as jamming the flow of discharging sand from a hopper and avalanching snow over the surface of mountains can be properly explained only based on the models addressing the transport and the dissipation of grains kinetic energy. (orig.)

  2. Investigation on hydraulic properties of compacted GMZ bentonite used as buffer/backfill material

    Directory of Open Access Journals (Sweden)

    Ye W. M.

    2016-01-01

    Full Text Available During the past decades, GMZ bentonite has been widely investigated for its use as buffer/backfill materials in China. Based on a comprehensive review of the former studies, achievements on experimental and theoretic works on the hydraulic aspects of compacted GMZ bentonite with consideration of temperature effects are presented in this paper. Water retention property of compacted GMZ bentonite depends on constraint conditions. Temperature effects on water-retention depend on constraint conditions and suction. The hysteresis behaviour is not obvious. Based on the test results, a revised water retention model was developed for considering the temperature effect. The saturated hydraulic conductivity of the densely compacted GMZ bentonite increases as dry density and temperature increases. A revised model, which considers temperature influence on water viscosity and the effective flow cross-sectional area of porous channels, for prediction of saturated hydraulic conductivity have been developed and verified. The unsaturated hydraulic conductivity of confined densely compacted GMZ bentonite samples decreases first and then increases with suction decrease from an initial value of 80 MPa to zero. With consideration of temperature effects and microstructure changes, a revised model for prediction of unsaturated hydraulic conductivity of compacted GMZ01 bentonite was proposed.

  3. 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.

  4. 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.

  5. Granular Material Flows with Interstitial Fluid Effects

    Science.gov (United States)

    Hunt, Melany L.; Brennen, Christopher E.

    2004-01-01

    The research focused on experimental measurements of the rheological properties of liquid-solid and granular flows. In these flows, the viscous effects of the interstitial fluid, the inertia of the fluid and particles, and the collisional interactions of the particles may all contribute to the flow mechanics. These multiphase flows include industrial problems such as coal slurry pipelines, hydraulic fracturing processes, fluidized beds, mining and milling operation, abrasive water jet machining, and polishing and surface erosion technologies. In addition, there are a wide range of geophysical flows such as debris flows, landslides and sediment transport. In extraterrestrial applications, the study of transport of particulate materials is fundamental to the mining and processing of lunar and Martian soils and the transport of atmospheric dust (National Research Council 2000). The recent images from Mars Global Surveyor spacecraft dramatically depict the complex sand and dust flows on Mars, including dune formation and dust avalanches on the slip-face of dune surfaces. These Aeolian features involve a complex interaction of the prevailing winds and deposition or erosion of the sediment layer; these features make a good test bed for the verification of global circulation models of the Martian atmosphere.

  6. 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

  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

    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

  8. Microgravity Granular Material Research (MGMR) Facility for ISS, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — TransAstra Corporation in collaboration with Grainflow Dynamics Inc. and the Colorado School of Mines proposes to develop a general purpose Micro-g Granular Material...

  9. 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...

  10. 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

  11. Laboratory gas injection tests on compacted bentonite buffer material for TRU waste disposal

    International Nuclear Information System (INIS)

    Namiki, Kazuto; Asano, Hidekazu; Takahashi, Shinichi; Shimura, Tomoyuki; Hirota, Ken

    2012-01-01

    Document available in extended abstract form only. In order to evaluate the gas transport mechanism through the TRU waste disposal facility, it is important to understand the gas migration phenomena based on the previous results of relevant research. The conventional large scale gas migration tests were mainly carried out for the purpose of grasp of a phenomenon, under realistic site environment. On the other hand, the acquisition and expansion of fundamental data to the bentonite buffer material that is assumed for use in Japan are important. The Radioactive Waste Management Funding and Research Center is carrying out a series of laboratory gas injection tests with a view to acquiring the data on gas migration properties under the assumed disposal conditions/materials, in view of the fact that there are few examples of previously conducted gas injections, either in Japan or other countries. Two sizes of bentonite columns were taken with heights of 50 mm and 25 mm. Both types of columns had a diameter of 60 mm and a dry density of 1.36 Mg/m 3 . The test apparatus consists of a lower loading platform, a bentonite column mold, and a top loading platform. The bentonite columns were fully saturated and then gas was injected from the lower part of the bentonite column. A load cell was installed in the lower loading platform, and the swelling pressure of the sample was measured. The bentonite columns which have 90% of initial saturation were selected to reduce the duration for saturation. Moreover, the stepwise pressurization (0.05 MPa/day) approach was adopted for gas injection test. Gas/water permeability in saturated bentonite In the typical gas injection test, the water outflow from the outer section started to increase rapidly after the gas injection pressure reached 1.7 MPa, and then the gas breakthrough occurred at the injection pressure of 1.8 MPa. Once the gas breakthrough occurred, the amount of gas outflow from outer section increased uniformly until the

  12. 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...

  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. Thermal Properties of Consolidated Granular Salt as a Backfill Material

    Science.gov (United States)

    Paneru, Laxmi P.; Bauer, Stephen J.; Stormont, John C.

    2018-03-01

    Granular salt has been proposed as backfill material in drifts and shafts of a nuclear waste disposal facility where it will serve to conduct heat away from the waste to the host rock. Creep closure of excavations in rock salt will consolidate (reduce the porosity of) the granular salt. This study involved measuring the thermal conductivity and specific heat of granular salt as a function of porosity and temperature to aid in understanding how thermal properties will change during granular salt consolidation accomplished at pressures and temperatures consistent with a nuclear waste disposal facility. Thermal properties of samples from laboratory-consolidated granular salt and in situ consolidated granular salt were measured using a transient plane source method at temperatures ranging from 50 to 250 °C. Additional measurements were taken on a single crystal of halite and dilated polycrystalline rock salt. Thermal conductivity of granular salt decreased with increases in temperature and porosity. Specific heat of granular salt at lower temperatures decreased with increasing porosity. At higher temperatures, porosity dependence was not apparent. The thermal conductivity and specific heat data were fit to empirical models and compared with results presented in the literature. At comparable densities, the thermal conductivities of granular salt samples consolidated hydrostatically in this study were greater than those measured previously on samples formed by quasi-static pressing. Petrographic studies of the consolidated salt indicate that the consolidation method influenced the nature of the porosity; these observations are used to explain the variation of measured thermal conductivities between the two consolidation methods. Thermal conductivity of dilated polycrystalline salt was lower than consolidated salt at comparable porosities. The pervasive crack network along grain boundaries in dilated salt impedes heat flow and results in a lower thermal conductivity

  15. 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.

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

    Directory of Open Access Journals (Sweden)

    Torres-Serra Joel

    2017-01-01

    Full Text Available 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.

  17. 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...... data on the granular subbase material. © 2013 American Society of Civil Engineers....... 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...... in order to determine the frost susceptibility of the material when it is contaminated by a deicing agent. Two series of three freezing tests with isothermal cooling has been conducted using identical saline gradient added through brine. Two types of cooling ramp, an automatic cooling and a manual cooling...

  18. Macroscopic bulk cohesion and torque for wet granular materials

    NARCIS (Netherlands)

    Roy, Sudeshna; Luding, Stefan; Weinhart, Thomas

    2015-01-01

    Wet granular materials in steady-state in a quasi-static flow have been studied with discrete particle simulations. The total torque is an experimentally accessible macroscopic quantity that can be used to investigate the shear strength, bulk cohesion and other properties of the materials. We report

  19. Ferromagnetic resonance studies of granular materials (abstract)

    Science.gov (United States)

    Rubinstein, Mark; Das, Badri; Chrisey, D. B.; Horwitz, J.; Koon, N. C.

    1994-05-01

    We have investigated the ferromagnetic resonance (FMR) spectra of several granular alloys displaying giant magnetoresistance (GMR). For this task, we have produced melt-spun ribbons of Fe5Co15Cu80 and Co20Cu80 by rapid quenching and thin films of Co80Cu20 by pulsed laser deposition. The salient feature of the FMR spectra is the increase of the resonance linewidth as a function of increasing annealing temperature. We have deconvoluted the FMR spectra to a single-domain powder pattern and a multidomain powder pattern. As a function of annealing temperature, the GMR of these samples attains a maximum value. Near the peak of the GMR curve, the FMR spectrum reveals that the ferromagnetic particles are half mono- and half multidomain. Since the maximum size of a single-domain particle is known, this enables us to estimate the spin diffusion length of the Cu conduction electrons. We have also demonstrated, theoretically and experimentally, that the appropriate demagnetizing field to apply to the ensemble of spherical magnetic particles that comprise our granular thin film is simply the field corresponding to the average magnetization.

  20. Magnetic resonance imaging of granular materials

    Science.gov (United States)

    Stannarius, Ralf

    2017-05-01

    Magnetic Resonance Imaging (MRI) has become one of the most important tools to screen humans in medicine; virtually every modern hospital is equipped with a Nuclear Magnetic Resonance (NMR) tomograph. The potential of NMR in 3D imaging tasks is by far greater, but there is only "a handful" of MRI studies of particulate matter. The method is expensive, time-consuming, and requires a deep understanding of pulse sequences, signal acquisition, and processing. We give a short introduction into the physical principles of this imaging technique, describe its advantages and limitations for the screening of granular matter, and present a number of examples of different application purposes, from the exploration of granular packing, via the detection of flow and particle diffusion, to real dynamic measurements. Probably, X-ray computed tomography is preferable in most applications, but fast imaging of single slices with modern MRI techniques is unmatched, and the additional opportunity to retrieve spatially resolved flow and diffusion profiles without particle tracking is a unique feature.

  1. Pore-scale Modelling of Capillarity in Swelling Granular Materials

    Science.gov (United States)

    Hassanizadeh, S. M.; Sweijen, T.; Nikooee, E.; Chareyre, B.

    2015-12-01

    Capillarity in granular porous media is a common and important phenomenon in earth materials and industrial products, and therefore has been studied extensively. To model capillarity in granular porous media, one needs to go beyond current models which simulate either two-phase flow in porous media or mechanical behaviour in granular media. Current pore-scale models for two-phase flow such as pore-network models are tailored for rigid pore-skeletons, even though in many applications, namely hydro-mechanical coupling in soils, printing, and hygienic products, the porous structure does change during two-phase flow. On the other hand, models such as Discrete Element Method (DEM), which simulate the deformable porous media, have mostly been employed for dry or saturated granular media. Here, the effects of porosity change and swelling on the retention properties was studied, for swelling granular materials. A pore-unit model that was capable to construct the capillary pressure - saturation curve was coupled to DEM. Such that the capillary pressure - saturation curve could be constructed for varying porosities and amounts of absorbed water. The study material was super absorbent polymer particles, which are capable to absorb water 10's to 200 times their initial weight. We have simulated quasi-static primary imbibition for different porosities and amounts of absorbed water. The results reveal a 3 dimensional surface between capillary pressure, saturation, and porosity, which can be normalized by means of the entry pressure and the effective water saturation to a unique curve.

  2. Properties improvement of paper mill sludge-based granular activated carbon fillers for fluidized-bed bioreactor by bentonite (Na) added and acid washing.

    Science.gov (United States)

    Li, Yanjie; Yue, Qinyan; Li, Wenhong; Gao, Baoyu; Li, Jinze; Du, Jiadan

    2011-12-15

    Properties improvement of paper mill sludge (PMS) based granular activated carbon fillers for fluidized-bed bioreactor (FBBR) was investigated in this study. Bentonite (Na) powders were blended in the dewatered paper mill sludge powders to strengthen the abrasion resistance strength of the fillers. Different acid washing treatments were studied to produce FBBR fillers with optimum performance. The results indicated that granulation was easy and the abrasion resistance strength of the fillers increased by 15% with 8 wt% of bentonite (Na) added. Acid washing treatment prior to activation had a better effect on the removal of Fe than post-activation acid washing treatment. HCl was the most appropriate acid during the acid washing treatment. The optimum acid washing treatment was carried out prior to activation with 2M HCl soaking for 6h. After acid washing treatment, the fillers with grain density of 1170 kg/m(3), specific surface area of 176 m(2)/g were obtained. Copyright © 2011 Elsevier B.V. All rights reserved.

  3. 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

  4. 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)

  5. Simulating granular materials by energy minimization

    Science.gov (United States)

    Krijgsman, D.; Luding, S.

    2016-11-01

    Discrete element methods are extremely helpful in understanding the complex behaviors of granular media, as they give valuable insight into all internal variables of the system. In this paper, a novel discrete element method for performing simulations of granular media is presented, based on the minimization of the potential energy in the system. Contrary to most discrete element methods (i.e., soft-particle method, event-driven method, and non-smooth contact dynamics), the system does not evolve by (approximately) integrating Newtons equations of motion in time, but rather by searching for mechanical equilibrium solutions for the positions of all particles in the system, which is mathematically equivalent to locally minimizing the potential energy. The new method allows for the rapid creation of jammed initial conditions (to be used for further studies) and for the simulation of quasi-static deformation problems. The major advantage of the new method is that it allows for truly static deformations. The system does not evolve with time, but rather with the externally applied strain or load, so that there is no kinetic energy in the system, in contrast to other quasi-static methods. The performance of the algorithm for both types of applications of the method is tested. Therefore we look at the required number of iterations, for the system to converge to a stable solution. For each single iteration, the required computational effort scales linearly with the number of particles. During the process of creating initial conditions, the required number of iterations for two-dimensional systems scales with the square root of the number of particles in the system. The required number of iterations increases for systems closer to the jamming packing fraction. For a quasi-static pure shear deformation simulation, the results of the new method are validated by regular soft-particle dynamics simulations. The energy minimization algorithm is able to capture the evolution of the

  6. 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

  7. 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

  8. 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,

  9. 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.

  10. Statistics of the Elastic Behavior of Granular Materials

    NARCIS (Netherlands)

    Kruyt, Nicolaas P.; Rothenburg, L.

    2001-01-01

    The elastic behaviour of isotropic assemblies of granular materials consisting of two-dimensional, bonded and non-rotating particles is studied from the micromechanical viewpoint. Discrete element simulations have been performed of assemblies of 50,000 particles with various coordination numbers

  11. Numerical simulation of liquefaction behaviour of granular materials ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    experimentation still remains quite problematic. Analytical treatments on the liquefaction beha- viour of granular materials generally assume con- tinuum behaviour. Several analytical methods based on non-linear elasticity, hypo elasticity, endochronic and plastic theory have been proposed by several researchers to predict ...

  12. Modelling of Granular Materials Using the Discrete Element Method

    DEFF Research Database (Denmark)

    Ullidtz, Per

    1997-01-01

    . Additional load pulses at the same load level gave decreasing plastic strain rate, in agreement with what is normally observed on granular materials. The resilient modulus was much lower than the stiffness of the elements and was decreasing with increasing deviator stress. At high deviator stresses...

  13. 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.

  14. Micromechanical Study of fabric evolution in quasi-static deformation of granular materials

    NARCIS (Netherlands)

    Kruyt, Nicolaas P.

    2012-01-01

    In micromechanical studies of granular materials, relations are investigated between macro-level, continuum characteristics and micro-level, (inter) particle characteristics. For quasi-static deformation of granular materials, the fabric tensor is an important micromechanical characteristic that

  15. Granular giant magnetoresistive materials and their ferromagnetic resonances

    Science.gov (United States)

    Rubinstein, M.; Das, B. N.; Koon, N. C.; Chrisey, D. B.; Horwitz, J.

    1994-11-01

    Ferromagnetic resonance (FMR) can reveal important information on the size and shape of the ferromagnetic particles which are dispersed in granular giant magnetoresistive (GMR) materials. We have investigated the FMR spectra of three different types of granular GMR material, each with different properties: (1) melt-spun ribbons of Fe5Co15Cu80 and Co20Cu80, (2) thin films of Co20Cu80 produced by pulsed laser deposition, and (3) a granular multilayer film of (Cu(50 A)/Fe(10 A)) x 50. We interpret the linewidth of these materials in as simple a manner as possible, as a 'powder pattern' of noninteracting ferromagnetic particles. The linewidth of the melt-spun ribbons is caused by a completely random distribution of crystalline anisotropy axes. The linewidth of these samples is strongly dependent upon the annealing temperature: the linewidth of the as-spun sample is 2.5 kOe (appropriate for single-domain particles) while the linewidth of a melt-spun sample annealed at 900 C for 15 min is 3.8 kOe (appropriate for larger, multidomain particles). The linewidth of the granular multilayer is attributed to a restricted distribution of shape anisotropies, as expected from a discontinuous multilayer, and is only 0.98 kOe with the magnetic field in the plane of the film.

  16. Ferromagnetic-resonance studies of granular giant-magnetoresistive materials

    Science.gov (United States)

    Rubinstein, M.; Das, B. N.; Koon, N. C.; Chrisey, D. B.; Horwitz, J.

    1994-07-01

    Ferromagnetic resonance (FMR) can reveal important information on the size and shape of the ferromagnetic particles which are dispersed in granular giant magnetoresistive (GMR) materials. We have investigated the FMR spectra of three different types of granular GMR material, each with different properties: (1) melt-spun ribbons of Fe5Co15Cu80 and Co20Cu80, (2) thin films of Co20Cu80 produced by pulsed laser deposition, and (3) a granular multilayer film of [Cu(50 Å)/Fe(10 Å)]×50. We interpret the linewidth of these materials in as simple a manner as possible, as a ``powder pattern'' of noninteracting ferromagnetic particles. The linewidth of the melt-spun ribbons is caused by a completely random distribution of crystalline anisotropy axes. The linewidth of these samples is strongly dependent upon the annealing temperature: the linewidth of the as-spun sample is 2.5 kOe (appropriate for single-domain particles) while the linewidth of a melt-spun sample annealed at 900 °C for 15 min is 4.5 kOe (appropriate for larger, multidomain particles). The linewidth of the granular multilayer is attributed to a restricted distribution of shape anisotropies, as expected from a discontinuous multilayer, and is only 0.98 kOe when the applied magnetic field is in the plane of the film.

  17. 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.

  18. 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

  19. Effective Thermal Expansion Property of Consolidated Granular Materials.

    Science.gov (United States)

    Küçük, Gülşad; Gonzalez, Marcial; Cuitiño, Alberto M

    2017-11-09

    Thermally-assisted compaction of granular materials is of keen interest in many engineering applications. A proper estimation of the material behavior of compacted granular materials is contingent upon the knowledge of microstructure formation, which is highly dependent on the bulk material properties and processing conditions, during the deformation stage. Originating from the pair interactions between particles, the macroscopic properties are obtained using various homogenization techniques and postulating continuum constitutive laws. While pioneers in this field have laid fundamental groundwork regarding effective medium descriptions, there exists a discrepancy between discrete and continuum level solutions. In our previous work, we elaborated a Particle Mechanics Approach (PMA) that integrates thermal contact and Hertzian deformation models to understand the thermo-mechanically-coupled consolidation problem. We also considered the analogous problem from the perspective of the conventional Continuum Mechanics Approach (CMA). In this study, following the multi-scale modeling framework, we propose an effective thermal expansion coefficient for the thermally-assisted compaction of granular materials.

  20. 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.

  1. Sintering of fly ash based composites with zeolite and bentonite addition for application in construction materials

    Directory of Open Access Journals (Sweden)

    Terzić Anja

    2017-01-01

    Full Text Available Due to pozzolanic characteristics, fly ash is commonly used as a cement replacement in construction composites. Addition of natural clays with sorption ability (i.e. zeolite and bentonite in to the fly ash based construction materials is of both scientific and industrial interest. Namely, due to the application of sorptive clay minerals, it is possible to immobilize toxic heavy metals from the composite structure. The thermal compatibility of fly ash and zeolite, as well as fly ash and bentonite, within the composite was observed during sintering procedure. The starting components were used in 1:1 ratio and they were applied without additional mechanical treatment. The used compaction pressure for the tablets was 2 t•cm-2. The sintering process was conducted at 1000ºC and 1200ºC for two hours in the air atmosphere. The mineralogical phase composition of the non-treated and sintered samples was analyzed using X-ray diffraction method. Scanning electron microscopy was applied in the analysis of the microstructure of starting and sintered samples. The thermal behavior was observed via DTA method. The influence of temperature on the properties of fly ash-zeolite and fly ash-bentonite composites was investigated. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. III 45008 and OI 172057

  2. Blast Wave Mitigation in Granular Materials

    Science.gov (United States)

    Pontalier, Quentin; Lhoumeau, Maxime; Frost, David

    2017-06-01

    A common technique to mitigate the blast wave from a high explosive is to surround the explosive with a layer of inert particles or liquid. In the case of a powder layer in spherical geometry, the spherically expanding shock wave that propagates first within the porous powder bed has a complex structure and induces the formation of force chains through particles in contact, shock propagation in the interstitial gas, and leads to shock compaction and deformation of the particle bed. Overall, the shock accelerates the particles and heats the gas in the pores and the partition of the total energy between kinetic and internal energy is primarily a function of the layer porosity and mass ratio of material to explosive. This energy partition is explored computationally with a multiphase hydrocode as a function of the bed parameters and compared with the case of a homogeneous liquid. The results are compared with experiments which track the strength of the blast wave emerging from the material layer as well as the material velocity using high-speed photography. For a given mass ratio, the strength of the blast wave transmitted into the air and the material velocity are significantly lower for particle beds than liquid layers due to energy dissipation during compaction of the bed.

  3. 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.

  4. 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.

  5. 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

  6. 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....

  7. 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.)

  8. Stress fluctuations and macroscopic stick-slip in granular materials.

    Science.gov (United States)

    Evesque, P; Adjémian, F

    2002-11-01

    This paper deals with the quasi-static regime of deformation of granular matter. It investigates the size of the Representative Elementary Volume (REV), which is the minimum packing size above which the macroscopic mechanical behaviour of granular materials can be defined from averaging. The first part uses typical results from recent literature and finds that the minimum REV contains in general 10 grains; this result holds true either for most experiments or for Discrete Element Method (DEM) simulation. This appears to be quite small. However, the second part gives a counterexample, which has been found when investigating uniaxial compression of glass spheres which exhibit stick-slip; we show in this case that the minimum REV becomes 10(7) grains. This makes the system not computable by DEM. Moreover, similarity between the Richter law of seism and the exponential statistics of stick-slip is stressed.

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

    NARCIS (Netherlands)

    Brouwers, Jos

    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

  10. 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)

  11. Engineering water repellency in granular materials for ground applications

    Science.gov (United States)

    Lourenco, Sergio; Saulick, Yunesh; Zheng, Shuang; Kang, Hengyi; Liu, Deyun; Lin, Hongjie

    2017-04-01

    Synthetic water repellent granular materials are a novel technology for constructing water-tight barriers and fills that is both inexpensive and reliant on an abundant local resource - soils. Our research is verifying its stability, so that perceived risks to practical implementation are identified and alleviated. Current ground stabilization measures are intrusive and use concrete, steel, and glass fibres as reinforcement elements (e.g. soil nails), so more sustainable approaches that require fewer raw materials are strongly recommended. Synthetic water repellent granular materials, with persistent water repellency, have been tested for water harvesting and proposed as landfill and slope covers. By chemically, physically and biologically adjusting the magnitude of water repellency, they offer the unique advantage of controlling water infiltration and allow their deployment as semi-permeable or impermeable materials. Other advantages include (1) volumetric stability, (2) high air permeability and low water permeability, (3) suitability for flexible applications (permanent and temporary usage), (4) improved adhesion aggregate-bitumen in pavements. Application areas include hydraulic barriers (e.g. for engineered slopes and waste containment), pavements and other waterproofing systems. Chemical treatments to achieve water repellency include the use of waxes, oils and silicone polymers which affect the soil particles at sub-millimetric scales. To date, our research has been aimed at demonstrating their use as slope covers and establishing the chemical compounds that develop high and stable water repellency. Future work will determine the durability of the water repellent coatings and the mechanics and modelling of processes in such soils.

  12. 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.)

  13. Cyclic Plane Strain Compression Tests on Dense Granular Materials

    Science.gov (United States)

    Koseki, Junichi; Karimi, Job Munene; Tsutsumi, Yukika; Maqbool, Sajjad; Sato, Takeshi

    A series of cyclic plane strain compression tests are performed under drained condition on dense Toyoura sand and compacted Chiba gravel, by using small-scale and large-scale apparatuses, respectively. Comparisons are made with results from monotonic loading tests. Local strain distributions are calculated by conducting image analyses of digital photographs taken at different stages of loading during each test. Based on these results, strain localization properties of dense granular materials are discussed, in particular focusing on possible effects of cyclic loading history.

  14. Ottawa Sand for Mechanics of Granular Materials (MGM) Experiment

    Science.gov (United States)

    2000-01-01

    What appear to be boulders fresh from a tumble down a mountain are really grains of Ottawa sand, a standard material used in civil engineering tests and also used in the Mechanics of Granular Materials (MGM) experiment. The craggy surface shows how sand grans have faces that can cause friction as they roll and slide against each other, or even causing sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. MGM uses the microgravity of space to simulate this behavior under conditions that carnot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. These images are from an Electron Spectroscopy for Chemical Analysis (ESCA) study conducted by Dr. Binayak Panda of IITRI for Marshall Space Flight Center (MSFC). (Credit: NASA/MSFC)

  15. Enhanced micropolar model for wave propagation in granular materials

    Science.gov (United States)

    Merkel, Aurélien; Luding, Stefan

    2016-04-01

    In the description of material elastic behavior, the classical theory of elasticity consists of a macroscopic material description. The material is not described at the micro-level by considering the displacement of the different particles in interaction, but is described as a continuum by considering macroscopic quantities as stress and strain. The classical elasticity theory can be viewed as first gradient of the displacement field approximation of the solid state theory and is valid in the long wavelength limit. Granular media, due to their micro-inhomogeneous character, are not well described by the standard continuum theory of elasticity. By contrast to classical continua where the sizes of the vibrating particles are assumed to be negligible compared to the distance between the particles, the sizes of the particles in a granular assembly are comparable to the distance between neighbors. In addition, considering the sliding, torsion and rolling resistances at the level of the contacts between the particles, a consistent description of the elasticity of a granular medium needs to take into account the rotational degrees of freedom of each individual particle. The elastic behavior of crystalline structures of monodisperse beads can be efficiently described by a discrete model, where the displacement and rotation of each individual bead are taken into account. Nevertheless, the discrete model can be solved analytically only for well-know regular crystalline structure, the case of a random assembly of beads is too complex for large systems. A continuum formulation is more suitable for random assemblies of beads different from the ideal crystalline case. The generalization of the classical elasticity theory accounting for the rotational degrees of freedom of point bodies is known as the Cosserat or micropolar theory. In this work, the vibration properties of a face-centered cubic structure of monodisperse granular crystal are predicted using a discrete model as

  16. 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.

  17. Permeation characteristics of compacted bentonite

    International Nuclear Information System (INIS)

    Banno, Katsunori; Nishi, Kenji; Yoshida, Hiroshi

    1991-01-01

    Bentonite has properties such as impermeability, hygroscopic swelling, which seem to make it a promising water cut-off material. In this research, performance tests were conducted with various types of compacted bentonite toward the application of bentonite to cut-off technology. (author)

  18. Simulation of triaxial response of granular materials by modified DEM

    Science.gov (United States)

    Wang, XiaoLiang; Li, JiaChun

    2014-12-01

    A modified discrete element method (DEM) with rolling effect taken into consideration is developed to examine macroscopic behavior of granular materials in this study. Dimensional analysis is firstly performed to establish the relationship between macroscopic mechanical behavior, mesoscale contact parameters at particle level and external loading rate. It is found that only four dimensionless parameters may govern the macroscopic mechanical behavior in bulk. The numerical triaxial apparatus was used to study their influence on the mechanical behavior of granular materials. The parametric study indicates that Poisson's ratio only varies with stiffness ratio, while Young's modulus is proportional to contact modulus and grows with stiffness ratio, both of which agree with the micromechanical model. The peak friction angle is dependent on both inter-particle friction angle and rolling resistance. The dilatancy angle relies on inter-particle friction angle if rolling stiffness coefficient is sufficiently large. Finally, we have recommended a calibration procedure for cohesionless soil, which was at once applied to the simulation of Chende sand using a series of triaxial compression tests. The responses of DEM model are shown in quantitative agreement with experiments. In addition, stress-strain response of triaxial extension was also obtained by numerical triaxial extension tests.

  19. Installing Mechanics of Granular Materials (MGM) experiment Test Cell

    Science.gov (United States)

    1996-01-01

    Astronaut Jay Apt installs Mechanics of Granular Materials (MGM0 test cell on STS-79. Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. MGM experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditions that carnot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. (Credit: NASA/John Space Center).

  20. Invited review: Clogging of granular materials in bottlenecks

    Directory of Open Access Journals (Sweden)

    Iker Zuriguel

    2014-12-01

    Full Text Available During the past decades, notable improvements have been achieved in the understanding of static and dynamic properties of granular materials, giving rise to appealing new concepts like jamming, force chains, non-local rheology or the inertial number. The 'saltcellar' can be seen as a canonical example of the characteristic features displayed by granular materials: an apparently smooth flow is interrupted by the formation of a mesoscopic structure (arch above the outlet that causes a quick dissipation of all the kinetic energy within the system. In this manuscript, I will give an overview of this field paying special attention to the features of statistical distributions appearing in the clogging and unclogging processes. These distributions are essential to understand the problem and allow subsequent study of topics such as the influence of particle shape, the structure of the clogging arches and the possible existence of a critical outlet size above which the outpouring will never stop. I shall finally offer some hints about general ideas that can be explored in the next few years.

  1. Symmetry analysis for uniaxial compression of a hypoplastic granular material

    Science.gov (United States)

    McCue, Scott W.; Johnpillai, I. Kenneth; Hill, James M.

    2005-11-01

    A variety of modelling approaches currently exist to describe and predict the diverse behaviours of granular materials. One of the more sophisticated theories is hypoplasticity, which is a stress-rate theory of rational continuum mechanics with a constitutive law expressed in a single tensorial equation. In this paper, a particular version of hypoplasticity, due to Wu [2], is employed to describe a class of one-dimensional granular deformations. By combining the constitutive law with the conservation laws of continuum mechanics, a system of four nonlinear partial differential equations is derived for the axial and lateral stress, the velocity and the void ratio. Under certain restrictions, three of the governing equations may be combined to yield ordinary differential equations, whose solutions can be calculated exactly. Several new analytical results are obtained which are applicable to oedometer testing. In general this approach is not possible, and analytic progress is sought via Lie symmetry analysis. A complete set or “optimal system” of group-invariant solutions is identified using the Olver method, which involves the adjoint representation of the symmetry group on its Lie algebra. Each element in the optimal system is governed by a system of nonlinear ordinary differential equations which in general must be solved numerically. Solutions previously considered in the literature are noted, and their relation to our optimal system identified. Two illustrative examples are examined and the variation of various functions occuring in the physical variables is shown graphically.

  2. 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

  3. 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

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

    NARCIS (Netherlands)

    Roy, Sudeshna; Luding, Stefan; Weinhart, Thomas

    2017-01-01

    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

  5. Understanding the effects of inter-particle contact friction on the elastic moduli of granular materials

    NARCIS (Netherlands)

    Taghizadeh Bajgirani, Kianoosh; Kumar, Nishant; Magnanimo, Vanessa; Luding, Stefan

    2015-01-01

    Understanding the mechanical stiffness of closely packed, dense granular systems is of interest in many fields, such as soil mechanics, material science and physics. The main difficulty arises due to discreteness and disorder in granular materials at the microscopic scale which requires a

  6. 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.

  7. Micro-mechanical study of stress path and initial conditions in granular materials using DEM

    Science.gov (United States)

    Dorostkar, Omid; Mirghasemi, Ali Asghar

    2016-03-01

    The macroscale response of granular materials under different loading conditions stems from the alteration of micromechanical properties during loading. Previous studies have used either physical experiments or discrete element method simulations to explore the effect of initial conditions and stress path on granular materials. However, microscale studies are not sufficient, especially for various loading paths. We study micromechanics of granular materials using the stress-force-fabric (SFF) relationship for a better understanding of the behavior of granular materials. Triaxial compression and extension tests are conducted on samples containing 1000 spherical particles, with periodic boundaries, and the effect of initial porosity is studied. In the next step, using the SFF relationship, we study the effect of anisotropic consolidation ratio. In addition to providing an appropriate explanation for shear strength out of evolution of anisotropy coefficients, our results show that anisotropic consolidation does not affect the micromechanical properties of granular materials in a way to change mobilized friction angle of sample at failure point.

  8. EFFECT OF PREPARATION METHOD OF Ni CATALYST USING BENTONITE AS THE SUPPORT MATERIAL

    Directory of Open Access Journals (Sweden)

    Hery Haerudin

    2010-06-01

    Full Text Available Nickel catalyst has been prepared impregnation and precipitation with nickel content of 20% and 25% each using bentonite as support material. The effects of the preparation method were studied using temperature programmed oxidation (TPO and temperature programmed reduction (TPR and by determination of its specific surface area. The activity of catalysts has been tested in the hydrogenation of palm oil. The catalyst with 20% of nickel and prepared by impregnation shows a single peak at 301°C, compared to catalyst with 25% of nickel prepared by the same method which has a peak at 304°C and a shoulder at 330°C. The reduction curves of both catalysts, those are prepared by impregnation, show a homogeneity indicated by a high main peak at 426°C (20% Ni and 430°C (25% Ni. The 25% nickel catalyst by impregnation has a shoulder at 508°C. The catalysts prepared by precipitation show peaks at 508°C and 661°C for 20% of Ni and peaks at 419°C and 511°C for 25% of Ni. The reduction curves of catalysts prepared by precipitation are significantly different from each other. Those are also very different comparing to the reduction curve of impregnated catalyst. The 20% precipitated nickel catalyst has a single peak at 540°C, but the 25% precipitated nickel catalyst shows peaks at 346°C and 503°C. The differences of peak position among the reduction curves of catalysts resulted in the differences of catalyst activities with the following order 20% Ni (impregnation > 25% Ni (impregnation > 20% Ni (precipitation > 25% Ni (precipitation.   Keywords: bentonite, nickel catalyst, hidrogenation

  9. 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.

  10. 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.

  11. 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

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

    African Journals Online (AJOL)

    precipitation method. The product was characterized by X-ray diffraction (XRD) and Scanning electron microscope (SEM). XRD results indicated the presence of free quartz in bentonite. The magnetic ferrite MnFe2O4 has spinel structure.

  13. 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

  14. Models of fluidized granular materials: examples of non-equilibrium stationary states

    Energy Technology Data Exchange (ETDEWEB)

    Puglisi, Andrea [Laboratoire de Physique Theorique Batiment 210, Universite de Paris-Sud, 91405 Orsay Cedex (France); Cecconi, Fabio [INFM Center for Statistical Mechanics and Complexity and Dipartimento di Fisica, Universita ' La Sapienza' , Piazzale A Moro 2, I-00185 Rome (Italy); Vulpiani, Angelo [Dipartimento di Fisica, Universita ' La Sapienza' , INFM Center for Statistical Mechanics and Complexity (SMC), INFN Sezione di Roma-1 ' La Sapienza' , Piazzale A Moro 2, I-00185, Rome (Italy)

    2005-06-22

    We review some models of granular materials fluidized by means of external forces, such as random homogeneous forcing with damping, vibrating plates, flow in an inclined channel and flow in a double well potential. All these systems show the presence of density correlations and non-Gaussian velocity distributions. These models are useful in understanding the role of a kinetically defined 'temperature' (in this case the so-called granular temperature) in a non-equilibrium stationary state. In the homogeneously randomly driven gas the granular temperature is different from that of the driving bath. Moreover, two different granular materials mixed together may stay in a stationary state with different temperatures. At the same time, the granular temperature determines (as in equilibrium systems) the escape time in a double well potential.

  15. 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)

  16. Impact damper with granular materials for multibody system

    Energy Technology Data Exchange (ETDEWEB)

    Yokomichi, I. [Kitakyushu College of Technology (Japan). Dept. of Mechanical Engineering; Araki, Y.; Jinnouchi, Y. [Kyushu Inst. of Technology, Kitakyushu (Japan). Dept. of Mechanical and Control Engineering; Inoue, J. [Nishi-Nippon Inst. of Technology, Miyako, Fukuoka (Japan)

    1996-02-01

    An efficient impact damper consists of a bed of granular materials moving in a container mounted on a multibody vibrating system. This paper deals with the damping characteristics of a multidegree-of-freedom (MDOF) system that is provided with the impact damper when the damper may be applied to any point of the system. In the theoretical analysis, the particle bed is assumed to be a mass which moves unidirectionally in a container, and collides plastically with its end. Equations of motion are developed for an equivalent single-degree-of-freedom (SDOF) system and attached damper mass with use made of the normal mode approach. The modal mass is estimated such that it represents the equivalent mass on the point of maximum displacement in each of the vibrating modes. The mass ratio is modified with the modal vector to include the effect of impact interactions. Results of the analysis are applied to the special case of a three-degree-of-freedom (3DOF) system, and the effects of the damper parameters including mode shapes and damper locations are determined. A digital model is also formulated to simulate the damped motion of the physical system.

  17. The transitional behaviour of avalanches in cohesive granular materials

    Science.gov (United States)

    Quintanilla, M. A. S.; Valverde, J. M.; Castellanos, A.

    2006-07-01

    We present a statistical analysis of avalanches of granular materials that partially fill a slowly rotated horizontal drum. For large sized noncohesive grains the classical coherent oscillation is reproduced, consisting of a quasi-periodic succession of regularly sized avalanches. As the powder cohesiveness is increased by decreasing the particle size, we observe a gradual crossover to a complex dynamics that resembles the transitional behaviour observed in fusion plasmas. For particle size below ~50 µm, avalanches lose a characteristic size, retain a short term memory and turn gradually decorrelated in the long term as described by a Markov process. In contrast, large grains made cohesive by coating them with adhesive microparticles display a distinct phenomenology, characterized by a quasi-regular succession of well defined small precursors and large relaxation events. The transition from a one-peaked distribution (noncohesive large beads) to a flattened distribution (fine cohesive beads) passing through the two-peaked distribution of cohesive large beads had already been predicted using a coupled-map lattice model, as the relaxation mechanism of grain reorganization becomes dominant to the detriment of inertia.

  18. Sustainable polysaccharide-based biomaterial recovered from waste aerobic granular sludge as a surface coating material

    NARCIS (Netherlands)

    Lin, Y. M.; Nierop, K.G.J.; Girbal-Neuhauser, E.; Adriaanse, M.; van Loosdrecht, M. C M

    To evaluate the possibility of utilizing polysaccharide-based biomaterial recovered from aerobic granular sludge as a coating material, the morphology, molecular weight distribution and chemical composition of the recovered biomaterial were investigated by atomic force microscopy, size exclusion

  19. Sustainable polysaccharide-based biomaterial recovered from waste aerobic granular sludge as a surface coating material

    NARCIS (Netherlands)

    Lin, Y.M.; Nierop, K.G.J.; Girbal-Neuhauser, E.; Adriaanse, M.; Van Loosdrecht, M.C.M.

    2015-01-01

    To evaluate the possibility of utilizing polysaccharide-based biomaterial recovered from aerobic granular sludge as a coating material, the morphology, molecular weight distribution and chemical composition of the recovered biomaterial were investigated by atomic force microscopy, size exclusion

  20. Influence of stress-path on pore size distribution in granular materials

    Science.gov (United States)

    Das, Arghya; Kumar, Abhinav

    2017-06-01

    Pore size distribution is an important feature of granular materials in the context of filtration and erosion in soil hydraulic structures. Present study focuses on the evolution characteristics of pore size distribution for numerically simulated granular assemblies while subjected to various compression boundary constrain, namely, conventional drained triaxial compression, one-dimensional or oedometric compression and isotropic compression. We consider the effects initial packing of the granular assembly, loose or dense state. A simplified algorithm based on Delaunay tessellation is used for the estimation of pore size distribution for the deforming granular assemblies at various stress states. The analyses show that, the evolution of pore size is predominantly governed by the current porosity of the granular assembly while the stress path or loading process has minimal influence. Further it has also been observed that pore volume distribution reaches towards a critical distribution at the critical porosity during shear enhanced loading process irrespective of the deformation mechanism either compaction or dilation.

  1. 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.

  2. The influence of the percent weight local material bentonite, quartz and magnetite of the capacity sorption Sr-90 in the radioactive waste

    International Nuclear Information System (INIS)

    Budiyono, M. E.

    1996-01-01

    An experimental investigation on the influence of the percent weight local material bentonite, quartz and magnetite of the capacity sorption on the nuclide of Sr-90 used as a backfill material has been done. The nuclide of Sr-90 has high toxicity, so an experimental investigation on its absorbability is necessary since this nuclide can not be dispersed to the environment. This investigation was carried out by varying some parameters which influence the sorption ability or sorptive capacity of the local material used. The variables investigated were the backfill material composition of bentonite/quartz and bentonite/magnetite. They were varied from 100/0 to 0/100% by weight. The sorption capacity of the maximum results was also determined. It can be concluded that the DF obtained from the local material of bentonite was 86.40, the quartz was 14.19 and the magnetite was 18.83. Varied the composition of local materials can improve DF. At the composition of 30% bentonite/70% quartz, the DF obtained was 183.33, where as at the composition of 80% bentonite/20% magnetite, the DF obtained was 165.35. The sorption capacity of bentonite 100% was 8.62 x 10 -3 μCi/g is the best sorption capacity. The initial activity of Sr-90 about 84.251 x 10 -3 μCi/ml. The best result of activity of Sr-90 nuclide as the sorption residue was about 4.55 x 10 -6 μCi/ml is still the range of safety limit if it dispersed to the environment, which is on in accordance with the maximum permissible concentration based on the safety limit of radiation work which is 2.7 x 10 -6 μCi/ml. (The Director General's Decree No. PN 03/180/DJ/89). (author)

  3. Relating Water and Air Flow Characteristics in Coarse Granular Materials

    DEFF Research Database (Denmark)

    Andreasen, Rune Røjgaard; Canga, Eriona; Kjærgaard, Charlotte

    2013-01-01

    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...

  4. 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...

  5. Sound wave propagation in weakly polydisperse granular materials

    NARCIS (Netherlands)

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

    2008-01-01

    Dynamic simulations of wave propagation are performed in dense granular media with a narrow polydisperse size-distribution and a linear contact-force law. A small perturbation is created on one side of a static packing and its propagation, for both P- and S-waves, is examined. A size variation

  6. 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

  7. Influence of polydispersity on micromechanics of granular materials

    NARCIS (Netherlands)

    Reza Shaebani, M.; Madadi, M.; Luding, Stefan; de Wolf, Ilja

    2012-01-01

    We study the effect of polydispersity on the macroscopic physical properties of granular packings in two and three dimensions. A mean-field approach is developed to approximate the macroscale quantities as functions of the microscopic ones. We show that the trace of the fabric and stress tensors are

  8. 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)

  9. 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.

  10. Characterization of granular phase change materials for thermal energy storage applications in fluidized beds

    International Nuclear Information System (INIS)

    Izquierdo-Barrientos, M.A.; Sobrino, C.; Almendros-Ibáñez, J.A.; Barreneche, C.; Ellis, N.; Cabeza, L.F.

    2016-01-01

    Highlights: • Granular PCMs are tested in 3D and 2D fluidized beds. • Density, particle size and angle of repose were measured for different granular PCMs. • DSC measurements confirm that there is no loss of material after fluidization. - Abstract: This work investigates commercially available granular phase change materials (PCMs) with different transition temperatures for the use of thermal-energy storage systems in fluidized beds. The hydrodynamic characteristics of granular PCMs were tested in cylindrical-3D and planar-2D fluidized beds. The density, particle size distribution and angle of repose were measured for various PCM materials. Further attrition studies were conducted with changes in particle surface from abrasion, which were characterized using a Scanning Electron Microscope (SEM). The results indicate that some materials with smaller particle size and thinner supporting structure can lose the paraffin during the fluidization process, when paraffin is in a liquid state. As a consequence, the particles agglomerate, and the bed defluidizes. For all of the tested materials, only GR50 (with a transition temperature of 50 °C) properly fluidizes when the paraffin is in the liquid state and has shown to endure >75 h of continuous operation and 15 melting-solidification cycles in a fluidized bed. Additional differential scanning calorimetry (DSC) measurements of the cycled particles did not show a decrease in energy storage capacity of the granular PCM, which corroborates that there is no loss of material after >75 h of fluidization.

  11. 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

  12. 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

  13. 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

  14. Non-Dissipative Structural Evolutions in Granular Materials

    Directory of Open Access Journals (Sweden)

    Pouragha Mehdi

    2017-01-01

    Full Text Available The structure of the contact network in granular assemblies can evolve due to either dissipative mechanisms such as sliding at contact points, or non-dissipative mechanisms through the phenomenon of contact gain and loss. Being associated with negligible deformations, non-dissipative mechanisms is actually active even in the small strain range of ~ 10−3, especially in the case of densely packed assemblies. Hence, from a constitutive modelling point of view, it is crucial to be able to estimate such non-dissipative evolutions since both elastic and plastic properties of granular assemblies highly depend on contact network characteristics. The current study proposes an analytical scheme that allows us to estimate the non-dissipative contact gain/loss regime in terms of directional changes in the average contact force. The probability distribution of contact forces is used to compute the number of lost contact for each direction. Similarly, the number of newly formed contacts is estimated by considering the probability distribution of the gap between neighbouring particles. Based on the directional contact gain/loss computed, the changes in coordination number and fabric anisotropy can be found which, together with statistical treatments of Love-Weber stress expression, form a complete system of equations describing the evolution of other controlling microvariables. Finally, the results of the calculations have been compared with DEM simulations which verify the accuracy of the proposed scheme.

  15. Non-Dissipative Structural Evolutions in Granular Materials

    Science.gov (United States)

    Pouragha, Mehdi; Wan, Richard

    2017-06-01

    The structure of the contact network in granular assemblies can evolve due to either dissipative mechanisms such as sliding at contact points, or non-dissipative mechanisms through the phenomenon of contact gain and loss. Being associated with negligible deformations, non-dissipative mechanisms is actually active even in the small strain range of 10-3, especially in the case of densely packed assemblies. Hence, from a constitutive modelling point of view, it is crucial to be able to estimate such non-dissipative evolutions since both elastic and plastic properties of granular assemblies highly depend on contact network characteristics. The current study proposes an analytical scheme that allows us to estimate the non-dissipative contact gain/loss regime in terms of directional changes in the average contact force. The probability distribution of contact forces is used to compute the number of lost contact for each direction. Similarly, the number of newly formed contacts is estimated by considering the probability distribution of the gap between neighbouring particles. Based on the directional contact gain/loss computed, the changes in coordination number and fabric anisotropy can be found which, together with statistical treatments of Love-Weber stress expression, form a complete system of equations describing the evolution of other controlling microvariables. Finally, the results of the calculations have been compared with DEM simulations which verify the accuracy of the proposed scheme.

  16. Simulation of size segregation in granular flow with material point method

    Directory of Open Access Journals (Sweden)

    Fei Minglong

    2017-01-01

    Full Text Available Segregation is common in granular flows consisting of mixtures of particles differing in size or density. In gravity-driven flows, both gradients in total pressure (induced by gravity and gradients in velocity fluctuation fields (often associated with shear rate gradients work together to govern the evolution of segregation. Since the local shear rate and velocity fluctuations are dependent on the local concentration of the components, understanding the co-evolution of segregation and flow is critical for understanding and predicting flows where there can be a variety of particle sizes and densities, such as in nature and industry. Kinetic theory has proven to be a robust framework for predicting this simultaneous evolution but has a limit in its applicability to dense systems where collisions are highly correlated. In this paper, we introduce a model that captures the coevolution of these evolving dynamics for high density gravity driven granular mixtures. For the segregation dynamics we use a recently developed mixture theory (Fan & Hill 2011, New J. Phys; Hill & Tan 2014, J. Fluid Mech. which captures the combined effects of gravity and fluctuation fields on segregation evolution in high density granular flows. For the mixture flow dynamics, we use a recently proposed viscous-elastic-plastic constitutive model, which can describe the multi-state behaviors of granular materials, i.e. the granular solid, granular liquid and granular gas mechanical states (Fei et al. 2016, Powder Technol.. The platform we use for implementing this model is a modified Material Point Method (MPM, and we use discrete element method simulations of gravity-driven flow in an inclined channel to demonstrate that this new MPM model can predict the final segregation distribution as well as flow velocity profile well. We then discuss ongoing work where we are using this platform to test the effectiveness of particular segregation models under different boundary conditions.

  17. 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

  18. Synchronized oscillations and acoustic fluidization in confined granular materials

    Science.gov (United States)

    Giacco, F.; de Arcangelis, L.; Ciamarra, M. Pica; Lippiello, E.

    2018-01-01

    According to the acoustic fluidization hypothesis, elastic waves at a characteristic frequency form inside seismic faults even in the absence of an external perturbation. These waves are able to generate a normal stress which contrasts the confining pressure and promotes failure. Here, we study the mechanisms responsible for this wave activation via numerical simulations of a granular fault model. We observe the particles belonging to the percolating backbone, which sustains the stress, to perform synchronized oscillations over ellipticlike trajectories in the fault plane. These oscillations occur at the characteristic frequency of acoustic fluidization. As the applied shear stress increases, these oscillations become perpendicular to the fault plane just before the system fails, opposing the confining pressure, consistently with the acoustic fluidization scenario. The same change of orientation can be induced by external perturbations at the acoustic fluidization frequency.

  19. 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.

  20. Using Space for a Better Foundation on Earth: Mechanics of Granular Materials. Educational Brief. Grades 5-8.

    Science.gov (United States)

    Alshibli, Khalid

    This publication presents a science activity and instructional information on mechanics of granular materials, interparticle friction and geometric interlocking between particles which is a fundamental concept in many fields like earthquakes. The activity described in this document focuses on the principal strength of granular materials,…

  1. Using Space for a Better Foundation on Earth: Mechanics of Granular Materials. Educational Brief. Grades 9-12.

    Science.gov (United States)

    Alshibli, Khalid

    This publication presents a science activity and instructional information on the mechanics of granular materials, interparticle friction and geometric interlocking between particles which is a fundamental concept in many fields like in the study of earthquakes. This document describes the Mechanics of Granular Materials (MGM) experiments which…

  2. Imaging natural materials with a quasi-microscope. [spectrophotometry of granular materials

    Science.gov (United States)

    Bragg, S.; Arvidson, R.

    1977-01-01

    A Viking lander camera with auxilliary optics mounted inside the dust post was evaluated to determine its capability for imaging the inorganic properties of granular materials. During mission operations, prepared samples would be delivered to a plate positioned within the camera's field of view and depth of focus. The auxiliary optics would then allow soil samples to be imaged with an 11 pm pixel size in the broad band (high resolution, black and white) mode, and a 33 pm pixel size in the multispectral mode. The equipment will be used to characterize: (1) the size distribution of grains produced by igneous (intrusive and extrusive) processes or by shock metamorphism, (2) the size distribution resulting from crushing, chemical alteration, or by hydraulic or aerodynamic sorting; (3) the shape and degree of grain roundness and surface texture induced by mechanical and chemical alteration; and (4) the mineralogy and chemistry of grains.

  3. On micromechanical characteristics of the critical state of two-dimensional granular materials

    NARCIS (Netherlands)

    Kruyt, Nicolaas P.; Rothenburg, L.

    2014-01-01

    In micromechanics of quasi-static deformation of granular materials, relationships are investigated between the macro-scale, continuum-mechanical characteristics, and the micro-scale characteristics at the particle and interparticle contact level. An important micromechanical quantity is the fabric

  4. Mass flow measurement of granular materials in aerial application. Part 2: Experimental model validation

    NARCIS (Netherlands)

    Grift, T.E.; Walker, J.T.; Hofstee, J.W.

    2001-01-01

    A system was developed to measure the mass flow of granular fertilizer material in aerial spreader ducts. The flow process was regarded as the sequential passage of clusters containing multiple particles with varying diameters. An optical sensor was used to measure the cluster lengths on the fly. In

  5. Quality improvement of granular secondary raw building materials by separation and cleansing techniques

    NARCIS (Netherlands)

    Xing, W.

    2004-01-01

    Contaminated granular wastes are potentially reusable because they have similar physical and chemical properties as primary raw building materials. From environmental aspects, the reuse must not result in polluting the soil, groundwater and surface water. Therefore the leaching values of inorganic

  6. Static and dynamic angles of repose in loose granular materials under reduced gravity

    NARCIS (Netherlands)

    Kleinhans, M.G.; Markies, H.; Vet, S.J. de; Veld, A.C. in 't; Postema, F.N.

    2011-01-01

    Granular materials avalanche when a static angle of repose is exceeded and freeze at a dynamic angle of repose. Such avalanches occur subaerially on steep hillslopes and wind dunes and subaqueously at the lee side of deltas. Until now it has been assumed that the angles of repose are independent

  7. 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.

  8. A reappraisal of the concept of the strong/weak force networks for granular materials

    NARCIS (Netherlands)

    Kruyt, Nicolaas P.

    2015-01-01

    The concept of the strong/weak force networks for granular materials has been proposed by Radjai et al [2]. The weak (strong) contact network consists of the contacts where the normal force is smaller (larger) than the average normal force. Based on results of particle simulations, Radjai et al [2

  9. A visco-elasto-plastic model for granular materials under simple shear conditions

    NARCIS (Netherlands)

    Redaelli, I.; di Prisco, C.; Vescovi, Dalila

    2016-01-01

    The numerical simulation of rapid landslides is quite complex mainly because constitutive models capable of simulating the mechanical behaviour of granular materials in the pre-collapse and post-collapse regimes are still missing. The goal of this paper is to introduce a constitutive model capable

  10. 3D DEM study of stick-slip behavior in partly saturated granular materials

    Science.gov (United States)

    Dorostkar, Omid; Johnson, Paul; Guyer, Robert; Marone, Chris; Carmeliet, Jan

    2017-04-01

    In the central part of faults, granular material is produced due to wear called fault gouge. During shearing, the fault gouge stores energy in the course of the stick phase, which can be suddenly released resulting in a stick-slip dynamics. The sudden release of accumulated energy leads to a drop in macroscopic friction coefficient, defined as ratio between shear stress and confining stress and to a sudden increase in kinetic energy of particles. Partial saturation of granular fault gouge with water can alter this dynamic stick-slip behavior. We use 3D discrete element method (DEM) simulations to study stick-slip dynamics in a wet granular fault gouge. The DEM model takes the presence of moisture into account introducing cohesive forces due to the presence of capillary bridges between the particles. We also consider viscous forces resistant to particles motion. Results show that in wet granular gouge, the macroscopic friction level attained during shearing is higher than in the dry state. The cohesive forces due to surface tension and Laplace pressure tend to maintain the contacts longer leading to longer and more stable stick phases, or higher recurrence times between successive slip events. This means that more energy can be stored leading to larger slip events characterized by larger drops in friction coefficient and larger thickness compaction. Our results are in line with experimental results on granular gouge of glass beads.

  11. 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.

  12. AASERT: Constitutive and Failure Behavior of Granular Materials

    National Research Council Canada - National Science Library

    Zhou, Min

    2000-01-01

    .... The objective of this research is to obtain material response data and constitutive characterization for these materials at strain rates of up to 105 S-1, to analyze the evolution of load-carrying...

  13. 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.

  14. Granular Material Scoop and Near-Vertical Lifting Feeder/Conveyor

    Science.gov (United States)

    Walton, Otis (Inventor); Vollmer, Hubert J. (Inventor)

    2017-01-01

    An integrated granular-material scoop and near-vertical lifting feeder/conveyor includes special connections and skirts between a bullnose rotating scoop and an open-helical screw that provides the rotations and material lift and evacuation. A conical working-face of the bullnose rotating scoop has symmetrically distributed graters and vents to break loose and force-in granular material from natural deposits and cargo holds. The bullnose rotating scoop and the open-helical screw its attached to move the material into a continuous layer on the inside surface of an outer stationary sheathing. A motor drive attached to the open-helical screw above at the delivery end provides the lifting force necessary.

  15. 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

  16. 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.

  17. 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

  18. Centrifugal Size-Separation Sieve for Granular Materials

    Science.gov (United States)

    Walton, Otis (Inventor); Dreyer, Christopher (Inventor); Riedel, Edward (Inventor)

    2015-01-01

    A centrifugal sieve and method utilizes centrifugal force in rapidly-rotated cylindrical or conical screens as the primary body force contributing to size segregation. Within the centrifugal acceleration field, vibration and/or shearing flows are induced to facilitate size segregation and eventual separation of the fines from the coarse material. Inside a rotating cylindrical or conical screen, a separately-rotated screw auger blade can be used to transport material along the rotating cylinder or conical wall and to induce shearing in the material.

  19. 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

  20. An experimental study of ultrasonic vibration and the penetration of granular material

    Science.gov (United States)

    Firstbrook, David; Worrall, Kevin; Timoney, Ryan; Suñol, Francesc; Gao, Yang

    2017-01-01

    This work investigates the potential use of direct ultrasonic vibration as an aid to penetration of granular material. Compared with non-ultrasonic penetration, required forces have been observed to reduce by an order of magnitude. Similarly, total consumed power can be reduced by up to 27%, depending on the substrate and ultrasonic amplitude used. Tests were also carried out in high-gravity conditions, displaying a trend that suggests these benefits could be leveraged in lower gravity regimes. PMID:28293134

  1. 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.

  2. Shock and Release Behaviour of Silica Based Granular Materials

    Science.gov (United States)

    Braithwaite, Chris; Perry, James; Taylor, Nicholas

    2017-06-01

    A large number of experiments have been conducted using the Cavendish single stage gas gun to investigate the dynamic properties of sand. The results included successful measurements of release in dry materials, demonstrating that this is markedly different to the loading path. The effect of moisture was examined and shown to be strongest where the material was close to saturation, at which point the microstructure of the exact sample configuration plays a significant role in the response. Finally, the effect of sample morphology was probed, and whilst it was found to be significant at low rates, in the shock regime impedance appears to be more strongly influenced by the presence of moisture or a fraction of small particle size debris.

  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. Computer-aided analysis for the Mechanics of Granular Materials (MGM) experiment

    Science.gov (United States)

    Parker, Joey K.

    1986-01-01

    The Mechanics of Granular Materials (MGM) program is planned to provide experimental determinations of the mechanics of granular materials under very low gravity conditions. The initial experiments will use small glass beads as the granular material, and a precise tracking of individual beads during the test is desired. Real-time video images of the experimental specimen were taken with a television camera, and subsequently digitized by a frame grabber installed in a microcomputer. Easily identified red tracer beads were randomly scattered throughout the test specimen. A set of Pascal programs was written for processing and analyzing the digitized images. Filtering the image with Laplacian, dilation, and blurring filters when using a threshold function produced a binary (black on white) image which clearly identified the red beads. The centroids and areas for each bead were then determined. Analyzing a series of the images determined individual red bead displacements throughout the experiment. The system can provide displacement accuracies on the order of 0.5 to 1 pixel is the image is taken directly from the video camera. Digitizing an image from a video cassette recorder introduces an additional repeatability error of 0.5 to 1 pixel. Other programs were written to provide hardcopy prints of the digitized images on a dot-matrix printer.

  5. Mixing Behaviors of Wet Granular Materials in a Pulsating Fluidized Bed

    Science.gov (United States)

    Lim, Eldin Wee Chuan

    2017-11-01

    The Discrete Element Method combined with Computational Fluid Dynamics was coupled with a capillary liquid bridge force model for computational studies of mixing behaviors in a gas fluidized bed containing wet granular materials. There was a high tendency for wet particles to form large agglomerates within which relative motions between adjacent particles were hindered. This resulted in much lower mixing efficiencies compared with fluidization of dry particles. Capillary liquid bridge forces were on average stronger than both fluid drag forces and particle-particle collision forces. Particle exchange between agglomerates was necessary for mixing to occur during fluidization of wet granular materials but required strong capillary liquid bridge forces to be overcome. When pulsation of the inlet gas flow was applied, voidage waves comprising regions of high and low particle concentration formed within the fluidized bed. This allowed particles to cluster and disperse repeatedly, thus facilitating exchange of particles between agglomerates and promoting mixing of particles throughout the fluidized bed. This points towards the possibility of utilizing pulsed fluidization as an effective means of improving mixing efficiencies in fluidized bed systems containing wet granular materials.

  6. 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.

  7. The influence of particle geometry and the intermediate stress ratio on the shear behavior of granular materials

    OpenAIRE

    Xie, Y H.; Yang, Z X.; Barreto, D.; Jiang, M D.

    2017-01-01

    The behavior of granular materials is very complex in nature and depends on particle shape, stress path, fabric, density, particle size distribution, amongst others. This paper presents a study of the effect of particle geometry (aspect ratio) on the mechanical behaviour of granular materials using the Discrete Element Method (DEM). This study discusses 3D DEM simulations of conventional triaxial and true triaxial tests. The numerical experiments employ samples with different particle aspect ...

  8. Localization and instability in sheared granular materials: Role of friction and vibration

    Science.gov (United States)

    Kothari, Konik R.; Elbanna, Ahmed E.

    2017-02-01

    Shear banding and stick-slip instabilities have been long observed in sheared granular materials. Yet, their microscopic underpinnings, interdependencies, and variability under different loading conditions have not been fully explored. Here we use a nonequilibrium thermodynamics model, the Shear Transformation Zone theory, to investigate the dynamics of strain localization and its connection to stability of sliding in sheared, dry, granular materials. We consider frictional and frictionless grains as well as the presence and absence of acoustic vibrations. 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 delocalize slip at these rates. Stick-slip is observed only for frictional 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. We analyze these observations in terms of possible transitions between rate strengthening and rate weakening response facilitated by a competition between shear-induced dilation and vibration-induced compaction. We discuss the implications of our results on dynamic triggering, quiescence, and strength evolution in gouge-filled fault zones.

  9. Devising a protocol-related statistical mechanics framework for granular materials.

    Science.gov (United States)

    Paillusson, Fabien

    2015-01-01

    Devising a statistical mechanics framework for jammed granular materials is a challenging task as those systems do not share some important properties required to characterize them with statistical thermodynamics tools. In a recent paper [Asenjo et al. Phys. Rev. Lett. 112, 098002 (2014)], a new definition of a granular entropy, which puts the protocol used to generate the packings at its roots, has been proposed. Following up these results, it is shown that the protocol used in Asenjo et al. can be recast as a canonical ensemble with a particular value of the temperature. Signature of gaussianity for large system sizes strongly suggests an asymptotic equivalence with a corresponding microcanonical ensemble where jammed states with certain basin volumes are sampled uniformly. We argue that this microcanonical ensemble is not Edwards's microcanonical ensemble and generalize this argument to other protocols.

  10. Rheology of wet granular materials under continuous shear: experiments and simulations

    Directory of Open Access Journals (Sweden)

    Badetti Michel

    2017-01-01

    Full Text Available The behaviour of wet granular media in shear flow is characterized by the dependence of apparent friction μ* and solid fraction Φs on the reduced pressure P* and the inertia number I. Reduced pressure, P* = σ22a2/F0, compares the applied normal stress σ22 on grains of diameter a to the tensile strength of contact F0 (proportional to the surface tension Г of the liquid and the beads diameter. A specifically modified rotational rheometer is used to characterize the response of model wet granular material to applied shear rate γ˙$\\dot \\gamma $ under controlled normal stress σ22. Discrete Element Method (DEM simulations in 3D are carried out in parallel and numerical results are compared with experimental ones. Cohesive, inertia, saturation and viscous effects on macroscopic coefficient of friction μ* and solid fraction Φs are discussed.

  11. 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.

  12. 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

  13. 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)

  14. An experimental study of low velocity impacts into granular material in reduced gravity

    Science.gov (United States)

    Murdoch, Naomi; Avila Martinez, Iris; Sunday, Cecily; Cherrier, Olivier; Zenou, Emanuel; Janin, Tristan; Cadu, Alexandre; Gourinat, Yves; Mimoun, David

    2016-04-01

    The granular nature of asteroid surfaces, in combination with the low surface gravity, makes it difficult to predict lander - surface interactions from existing theoretical models. Nonetheless, an understanding of such interactions is particularly important for the deployment of a lander package. This was demonstrated by the Philae lander, which bounced before coming to rest roughly 1 kilometer away from its intended landing site on the surface of comet 67P/Churyumov-Gerasimenko before coming to rest (Biele et al., 2015). In addition to being important for planning the initial deployment, information about the acceleration profile upon impact is also important in the choice of scientific payloads that want to exploit the initial landing to study the asteroid surface mechanical properties (e.g., Murdoch et al., 2016). Using the ISAE-SUPAERO drop tower, we have performed a series of low-velocity collisions into granular material in low gravity. Reduced-gravity is simulated by releasing a free-falling projectile into a surface container with a downward acceleration less than that of Earth's gravity. The acceleration of the surface is controlled through the use an Atwood machine, or a system of pulleys and counterweights. In reducing the effective surface acceleration of the granular material, the confining pressure will be reduced, and the properties of the granular material will become more representative of those on an asteroid's surface. In addition, since both the surface and projectile are falling, the projectile requires a minimum amount of time to catch the surface before the collision begins. This extended free-fall increases the experiment duration, making it easier to use accelerometers and high-speed cameras for data collection. The experiment is built into an existing 5.5 m drop-tower frame and has required the custom design of all components, including the projectile, surface sample container, release mechanism and deceleration system (Sunday et al., 2016

  15. 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

  16. 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.

  17. 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

  18. 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.

  19. Thermal properties of a new ecological building material / Granular cork embedded in white cement

    Directory of Open Access Journals (Sweden)

    Cherki Abou-bakr

    2014-04-01

    Full Text Available Cork, natural and renewable product, has thermal and acoustic properties very interesting because of its microstructure and porosity representing a significant portion of its apparent volume; it’s coming from Moroccan Maamora’s forest. This work is a contribution to understand the thermal behaviour of the composite material based on granular cork embedded in white cement. An experimental investigation of its thermal properties was mainly performed using the asymmetrical device of transient Hot Plate method. The effect of granular cork size on the thermal properties of the mixture was studied. The experimental study of this sustainable material aims to characterize its thermal properties and then compare them with those of white cement without cork for motivate the proposal that this composite material will be used as walls insulator. A comparison of the energy performances of the composite material and white cement was made; it allows deducing a very interesting energy gain. The findings of the experiments indicate that the composite is better than white cement in term of thermal insulation, energy storage capacity and lightness. So, it can be used to realize the internal walls insulation. Its utilization should contribute to the improvement of the energy efficiency in building especially that this is a mixture based on a sustainable and renewable material.

  20. 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.

  1. 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.)

  2. 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.

  3. Contributions to the validation of the CJS model for granular materials

    Science.gov (United States)

    Elamrani, Khadija

    1992-07-01

    Behavior model validation in the field of geotechnics is addressed, with the objective of showing the advantages and limits of the CJS (Cambou Jafari Sidoroff) behavior model for granular materials. Several levels are addressed: theoretical analysis of the CJS model to reveal consistence and first capacities; shaping (followed by validation by confrontation with other programs) of a computation code by finite elements (FINITEL) to integrate this model and prepare it for complex applications; validation of the code/model structure thus constituted by comparing its results to those of experiments in the case of nonhomogeneous (superficial foundations) problems.

  4. Rheology of wet granular materials in shear flow: experiments and discrete simulations

    Directory of Open Access Journals (Sweden)

    Badetti Michel

    2016-01-01

    Full Text Available The behaviour of wet granular media in shear flow is characterized by the dependence of apparent friction μ* and solid fraction ΦS on the reduced pressure P* and the inertia number I. Reduced pressure, P*= σ22a2/F0, compares the applied normal stress σ22 on grains of diameter a to the tensile strength of contact F0 (proportional to the surface tension Γ of the liquid and the beads diameter. A specifically modified rotational rheometer is used to characterize the response of model wet granular material (beads with diameter of submillimetric range to applied shear rate γ under controlled normal stress σ22. Discrete Element Method (DEM simulations in 3D are carried out in parallel and numerical results are compared with experimental ones. As P* is reduced, an increase of the apparent friction coefficient μ*=σ12/σ22, measured in the critical state and in slow flows with inertial effects is observed. While the agreement between experiments and simulations is good for dry materials as well as for wet materials in the quasistatic limit (I→0, some differences appear at finite I, for which some possible origins are discussed.

  5. Influencia de la inclusión de desecho de PVC sobre el CBR de un material granular tipo subbase

    Directory of Open Access Journals (Sweden)

    Edgar Rodríguez Rincón

    2006-07-01

    Full Text Available En Colombia, los materiales granulares de alta calidad para la conformación de estructuras de pavimentos flexibles son de difícil obtención. En algunas ocasiones el Ingeniero de carreteras debe trabajar con materiales granulares que no cumplen los requisitos mínimos de calidad de la especificación vial pertinente. En este caso el Ingeniero debe intentar mejorar las propiedades del material ya sea por medios mecánicos o químicos. En la presente investigación se utilizó desecho de PVC como material de adición, para modificar el comportamiento de una subbase granular. A partir de ensayos de Proctor y CBR se comparó el comportamiento del material natural, y mezclado con diferentes proporciones del desecho de PVC. Los resultados de la investigación muestran que el CBR de una mezcla de material granular, tipo subbase, y material de desecho, presenta un incremento notable. Además, la mezcla modificada logra cambiar el peso unitario del material, obteniéndose una mezcla con mayor resistencia y menor peso.In Colombia, the granular materials of high quality for the conformation of flexible pavements structures are of difficult obtaining. In some cases the Engineer of highways must work with granular materials that do not fulfill the requirements of minimum quality standards of the pertinent road specification. In this case the Engineer must try to improve the properties of the material either. In the present investigation, PVC remainders were used like adding material, to modify the behavior of a granular subbase. From tests of Proctor and CBR, the behavior of the natural and mixed material with different proportions of the PVC remainder was compared. The results of the investigation shown that the CBR of a mixture of granular material type subbase and the remainder material, present a remarkable increment. In addition, the modified mixture manages to modify the unitary weight of the material, obtaining a mixture with greater resistance and

  6. 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.)

  7. Investigation of performance of programming approaches and languages used for numerical simulation of granular material by the discrete element method

    Science.gov (United States)

    Balevičius, R.; Džiugys, A.; Kačianauskas, R.; Maknickas, A.; Vislavičius, K.

    2006-09-01

    Performance of programming approaches and languages used for the development of software codes for numerical simulation of granular material dynamics by the discrete element method (DEM) is investigated. The granular material considered represents a space filled with discrete spherical visco-elastic particles, and the behaviour of material under imposed conditions is simulated using the DEM. The object-oriented programming approach (implemented via C++) was compared with the procedural approach (using FORTRAN 90 and OBJECT PASCAL) in order to test their efficiency. The identical neighbour-searching algorithm, contact forces model and time integration method were implemented in all versions of codes. Two identical representative examples of the dynamic behaviour of granular material on a personal computer (compatible with IBM PC) were solved. The results show that software based on procedural approach runs faster in compare with software based on OOP, and software developed by FORTRAN 90 runs faster in compare with software developed by OBJECT PASCAL.

  8. 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)

  9. 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.

  10. Mechanics of Granular Materials (MGM0 Flight Hardware in Bench Test

    Science.gov (United States)

    2000-01-01

    Engineering bench system hardware for the Mechanics of Granular Materials (MGM) experiment is tested on a lab bench at the University of Colorado in Boulder. This is done in a horizontal arrangement to reduce pressure differences so the tests more closely resemble behavior in the microgravity of space. Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. MGM experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditions that carnot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. (Credit: University of Colorado at Boulder).

  11. Measure Advancing, Receding and Dynamic Contact Angles of granular materials in a close column

    Science.gov (United States)

    Callegari, Gerardo; Li, Minglu; Moghtadernejad, Sara; Drazer, German

    2017-11-01

    Wetting properties of granular materials are usually obtained by the Washburn column technique. One problem is that the effective contact angle measured is dynamic and variable. The open column technique also allows to measure static advancing contact angle when the interface stops because the driving capillary pressure is balanced by the hydrostatic pressure. However, when particle diameters are in the range of tens of microns the static condition cannot be achieved at practical heights. Also, the open column device cannot be used to measure receding contact angles or contact angles of non-wetting liquids. Dynamics of a close column filled with granular material of different particle sizes where the liquid mass, the enclosed air pressure and the front position are monitored as a function of time is studied. Contact angle is calculated in dynamic and advancing static conditions. Then, a Syringe pump is used to increase the pressure inside the column so that the receding contact angle can also be studied. Supplementary experiments with a reference liquid that completely wets the powder are performed. Using a second liquid decouples the properties of the bed from the result and allows to measure the contact angles without making assumptions on the pore size or geometry.

  12. 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

  13. 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

  14. Modeling granular materials as compressible nonlinear fluids: Heat transfer boundary value problems

    Directory of Open Access Journals (Sweden)

    Mehrdad Massoudi

    2006-01-01

    Full Text Available We discuss three boundary value problems in the flow and heat transfer analysis in flowing granular materials: (i the flow down an inclined plane with radiation effects at the free surface; (ii the natural convection flow between two heated vertical walls; (iii the shearing motion between two horizontal flat plates with heat conduction. It is assumed that the material behaves like a continuum, similar to a compressible nonlinear fluid where the effects of density gradients are incorporated in the stress tensor. For a fully developed flow the equations are simplified to a system of three nonlinear ordinary differential equations. The equations are made dimensionless and a parametric study is performed where the effects of various dimensionless numbers representing the effects of heat conduction, viscous dissipation, radiation, and so forth are presented.

  15. 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.

  16. Bentonite porewater chemistry

    OpenAIRE

    MICHAEL OCHS; BARBALA LOTHENBA; 柴田 雅博; 油井 三和

    1999-01-01

    Porewater composition in a compacted bentonite is dependent on the composition of the surrounding groundwater, and on the characteristics of the bentonite itself. Two mechanisms through which bentonite influences the respective porewater composition are distinguished: sulface chemical reactions (ion exchange, surface complexation) on smectite and dissolution of minerals and soluble impurities included in bentonite. This report provides the results of different activities related to the defini...

  17. Bentonite modification with pillarization method using metal stannum

    Science.gov (United States)

    Widjaya, Robert R.; Juwono, Ariadne L.; Rinaldi, Nino

    2017-11-01

    Clay minerals have received considerable attention in the last years because of their environmental compatibility, low cost, high selectivity, and operational simplicity. Although clays are very useful for many application in the field of catalysis, they have main disadvantage: their lack of pore volume and spesific surface area. Porosity and stability of these materials are improved by pillaring the clay layers with SnCl4, which leads to materials known as pillared clays (PILC). This research aims were to characterize the Bentonite and Sn-Bentonite as catalysts for cracking and oligomerization. The Sn-Bentonite was prepared by pillarization method with a variation in metal ratio of 5 mmol dan 10 mmol.gr-1 of bentonit. The catalyst characterized by X-ray Diffraction, X-ray Fluorescence, Fourier Transform Infra Red, Brunauer Emmett Teller, Thermogravimetric Analysis. The results showed that the Sn-Bentonite catalyst had large basal spacing and good porous structure, and the specific surface areas increased. XRF detected the Sn in the Bentonite and TGA results showed the ability Sn-Bentonite in receiving heat. FTIR test showed two type of acidity, broansted and lewis acid. The characterized results indicated that Sn-Bentonite with metal ratio 5 mmol.gr-1 better than Sn-Bentonite with metal ratio 10 mmol.gr-1, in which there was a significant increase the basal spacings, specific surface area, and pore volume. The TGA results for Sn-Bentonite appeared to be more thermally stable than Bentonite.

  18. Efficient Voronoi volume estimation for DEM simulations of granular materials under confined conditions

    Science.gov (United States)

    Frenning, Göran

    2015-01-01

    When the discrete element method (DEM) is used to simulate confined compression of granular materials, the need arises to estimate the void space surrounding each particle with Voronoi polyhedra. This entails recurring Voronoi tessellation with small changes in the geometry, resulting in a considerable computational overhead. To overcome this limitation, we propose a method with the following features:•A local determination of the polyhedron volume is used, which considerably simplifies implementation of the method.•A linear approximation of the polyhedron volume is utilised, with intermittent exact volume calculations when needed.•The method allows highly accurate volume estimates to be obtained at a considerably reduced computational cost. PMID:26150975

  19. 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.

  20. 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.

  1. Evolution of the temperature distribution of granular material in a horizontal rotating cylinder

    Science.gov (United States)

    Yohannes, Bereket; Emady, Heather; Anderson, Kellie; Javed, Maham; Paredes, Ingrid J.; Muzzio, Fernando J.; Borghard, William G.; Glasser, Benjamin J.; Cuitiño, Alberto M.

    2017-06-01

    Accurate prediction of the particles' temperature distribution and the time required to heat up the particles is important to maintain good quality products and economical processes for several industrial processes that involve thermal treatment. However, we do not have quantitative models to predict the average temperature or particles' temperature distribution accurately. In this article, we carry out DEM simulations and compute the temporal and spatial evolution of the distribution of the particles' temperature in rotating cylinders. We present typical examples for different particle properties and operating conditions. The temperature distribution follows what is referred to as a uniform distribution with well defined mean and standard deviation values. Our analysis of these statistical parameters can assist in the prediction of the time required to heat up granular materials and the design of efficient processes.

  2. Computer-aided analysis for the Mechanics of Granular Materials (MGM) experiment, part 2

    Science.gov (United States)

    Parker, Joey K.

    1987-01-01

    Computer vision based analysis for the MGM experiment is continued and expanded into new areas. Volumetric strains of granular material triaxial test specimens have been measured from digitized images. A computer-assisted procedure is used to identify the edges of the specimen, and the edges are used in a 3-D model to estimate specimen volume. The results of this technique compare favorably to conventional measurements. A simplified model of the magnification caused by diffraction of light within the water of the test apparatus was also developed. This model yields good results when the distance between the camera and the test specimen is large compared to the specimen height. An algorithm for a more accurate 3-D magnification correction is also presented. The use of composite and RGB (red-green-blue) color cameras is discussed and potentially significant benefits from using an RGB camera are presented.

  3. Bayesian calibration of microCT-based DEM simulations for predicting the effective elastic response of granular materials

    NARCIS (Netherlands)

    Cheng, Hongyang; Pellegrino, Antonio; Magnanimo, Vanessa

    2017-01-01

    A novel approach is presented for calibrating discrete element method (DEM) simulations of granular materials based on the sequential Bayesian parameter estimation over the experimental stress–strain responses. The initial DEM packing is bridged with microscopic computed tomography (microCT) images

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. 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...... on the hydraulic conductivity at the ice-bed interface. Grain-fluid feedbacks can cause complex material properties that vary over time, and which may be of importance for glacier stick-slip behavior....... of subglacial sediment to the shear stress of an overriding glacier. In this study, we present a new methodology designed to simulate subglacial deformation using a coupled numerical model for computational experiments on grain-fluid mixtures. The granular phase is simulated on a per-grain basis by the discrete...... 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...

  9. 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.

  10. Americium, Cesium, and Plutonium Colloid-Facilitated Transport in a Groundwater/Bentonite/Fracture Fill Material System: Column Experiments and Model Results

    Science.gov (United States)

    Dittrich, T. M.; Boukhalfa, H.; Reimus, P. W.

    2014-12-01

    The objective of this study was to investigate and quantify the effects of desorption kinetics and colloid transport on radionuclides with different sorption affinities. We focused on quantifying transport mechanisms important for upscaling in time and distance. This will help determine the long-term fate and transport of radionuclides to aid in risk assessments. We selected a fractured/weathered granodiorite at the Grimsel Test Site (GTS) in Switzerland as a model crystalline rock repository system because the system has been thoroughly studied and field experiments involving radionuclides have already been conducted. Working on this system provides a unique opportunity to compare lab experiments with field-scale observations. Weathered fracture fill material (FFM) and bentonite used as backfill at the GTS were characterized (e.g., BET, SEM/EDS, QXRD), and batch and breakthrough column experiments were conducted. Solutions were prepared in synthetic groundwaters that matched the natural water chemistry. FFM samples were crushed, rinsed, sieved (150-355 μm), and equilibrated with synthetic groundwater. Bentonite was crushed, sodium-saturated, equilibrated with synthetic groundwater, and settled to yield a stable suspension. Suspensions were equilibrated with Am, Cs, or Pu. All experiments were conducted with Teflon®materials to limit sorption to system components. After radionuclide/colloid injections reached stability, radionuclide-free solutions were injected to observe the desorption and release behavior. Aliquots of effluent were measured for pH, colloid concentration, and total and dissolved radionuclides. Unanalyzed effluent from the first column was then injected through a second column of fresh material. The process was repeated for a third column and the results of all three breakthrough curves were modeled with a multi-site/multi-rate MATLAB code to elucidate the sorption rate coefficients and binding site densities of the bentonite colloids and

  11. 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

  12. 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

  13. 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)

  14. 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.

  15. 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

  16. 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.

  17. Use of steel slag as a granular material: volume expansion prediction and usability criteria.

    Science.gov (United States)

    Wang, George; Wang, Yuhong; Gao, Zhili

    2010-12-15

    The theoretical equation for predicting volume expansion of steel slag is deduced based on both chemical reaction and physical changes of free lime in steel slag during the hydration process. Laboratory volume expansion testing is conducted to compare the results with the theoretical volume expansion. It is proved that they correlated well. It is furthermore experimentally proved that certain volume expansion of steel slag can be absorbed internally by the void volume in bulk steel slag under external surcharge weight making the apparent volume expansion equal zero. The minimum (lowest) absorbable void volume is approximately 7.5%, which is unrelated to the free lime content. A usability criterion is then developed based on the volume expansion of steel slag (%) and the minimum percentage of the volume that can take the volume expansion of steel slag (%). Eventually the criterion (relationship) is established based on the free lime content, the specific gravity and bulk relative gravity of a specific steel slag sample. The criteria can be used as guidance and specification for the use of steel slag and other expansion-prone nonferrous slags, copper, nickel for instance as a granular material in highway construction. Copyright © 2010 Elsevier B.V. All rights reserved.

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

    Science.gov (United States)

    Zhang, Yue; Behringer, Robert

    2017-06-01

    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.

  19. 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.

  20. Micro-macro transition and simplified contact models for wet granular materials

    Science.gov (United States)

    Roy, Sudeshna; Singh, Abhinendra; Luding, Stefan; Weinhart, Thomas

    2016-11-01

    Wet granular materials in a quasistatic steady-state shear flow have been studied with discrete particle simulations. Macroscopic quantities, consistent with the conservation laws of continuum theory, are obtained by time averaging and spatial coarse graining. Initial studies involve understanding the effect of liquid content and liquid properties like the surface tension on the macroscopic quantities. Two parameters of the liquid bridge contact model have been identified as the constitutive parameters that influence the macroscopic rheology (i) the rupture distance of the liquid bridge model, which is proportional to the liquid content, and (ii) the maximum adhesive force, as controlled by the surface tension of the liquid. Subsequently, a correlation is developed between these microparameters and the steady-state cohesion in the limit of zero confining pressure. Furthermore, as second result, the macroscopic torque measured at the walls, which is an experimentally accessible parameter, is predicted from our simulation results with the same dependence on the microparameters. Finally, the steady- state cohesion of a realistic non-linear liquid bridge contact model scales well with the steady-state cohesion for a simpler linearized irreversible contact model with the same maximum adhesive force and equal energy dissipated per contact.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. Clast-fabric development in a shearing granular material: Implications for subglacial till and fault gouge

    Science.gov (United States)

    Hooyer, T.S.; Iverson, N.R.

    2000-01-01

    Elongate clasts in subglacial till and in fault gouge align during shearing, but the relation between clast-fabric strength and cumulative shear strain for such materials is effectively unknown. This relation was explored in experiments with a large ring-shear device in which a till and a viscous putty that contained isolated clasts were sheared to high strains. As expected, rotation of clasts in the putty is closely approximated by the theory of G.B. Jeffrey, who derived the orbits of rigid ellipsoids in a slowly shearing fluid. Clast rotation in the till, however, is strikingly different. Rather than orbiting through the shear plane as predicted by Jeffery, most clasts rotate into the shear plane and remain there, resulting in strong fabrics regardless of the aspect ratios and initial orientations of clasts. This divergent behavior is likely due to slip of the till matrix along the surfaces of clasts, which is a natural expectation in a granular material but violates the no-slip condition of Jeffery's model. These results do not support the widespread belief that subglacial till deformation results in weak clast fabrics. Thus, many tills with weak fabrics thought to have been sheared subglacially to high strains, like many basal tills of the Laurentide Ice Sheet, may have been sheared only slightly with little effect on either ice-sheet dynamics or sediment transport. In addition, these results indicate that in simple shear the rotation of clasts in till and in fault gouge is best analyzed with the model of A. March, who treated inclusions as passive markers.

  6. 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.

  7. Centrifugal Sieve for Gravity-Level-Independent Size Segregation of Granular Materials

    Science.gov (United States)

    Walton, Otis R.; Dreyer, Christopher; Riedel, Edward

    2013-01-01

    Conventional size segregation or screening in batch mode, using stacked vibrated screens, is often a time-consuming process. Utilization of centrifugal force instead of gravity as the primary body force can significantly shorten the time to segregate feedstock into a set of different-sized fractions. Likewise, under reduced gravity or microgravity, a centrifugal sieve system would function as well as it does terrestrially. When vibratory and mechanical blade sieving screens designed for terrestrial conditions were tested under lunar gravity conditions, they did not function well. The centrifugal sieving design of this technology overcomes the issues that prevented sieves designed for terrestrial conditions from functioning under reduced gravity. These sieves feature a rotating outer (cylindrical or conical) screen wall, rotating fast enough for the centrifugal forces near the wall to hold granular material against the rotating screen. Conventional centrifugal sieves have a stationary screen and rapidly rotating blades that shear the granular solid near the stationary screen, and effect the sieving process assisted by the airflow inside the unit. The centrifugal sieves of this new design may (or may not) have an inner blade or blades, moving relative to the rotating wall screen. Some continuous flow embodiments would have no inner auger or blades, but achieve axial motion through vibration. In all cases, the shearing action is gentler than conventional centrifugal sieves, which have very high velocity differences between the stationary outer screen and the rapidly rotating blades. The new design does not depend on airflow in the sieving unit, so it will function just as well in vacuum as in air. One advantage of the innovation for batch sieving is that a batch-mode centrifugal sieve may accomplish the same sieving operation in much less time than a conventional stacked set of vibrated screens (which utilize gravity as the primary driving force for size separation

  8. 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

  9. 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

  10. Measurement of pH of the Compacted Bentonite under the Reducing Condition

    OpenAIRE

    Nessa, Syeda Afsarun; Idemitsu, Kazuya; Yamasaki, Yosuke; Inagaki, Yaohiro; Arima, Tatsumi

    2007-01-01

    Compacted bentonite and carbon steel have been considered as the good buffer and over-pack materials in the repositories of high-level radioactive waste disposal. Sodium bentonite, Kunipia-F contains approximately 95wt% of montmorillonite. It has a high cation-exchange capacity and a high specific surface area, and its properties determine the behavior of bentonite. The pH of the pore water in compacted bentonite is an extremely important parameter because of its influence on radionuclide sol...

  11. 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.)

  12. 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.)

  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. Investigation of the resilient behavior of granular base materials with simple test apparatus

    NARCIS (Netherlands)

    Araya, A.A.; Huurman, M.; Molenaar, A.A.A.; Houben, L.J.M.

    2012-01-01

    In many developing countries, where resources are at premium, thin asphalt layers or chip seals are widely used to provide a durable all weather pavement surfacing. In such pavements the role of granular layers is very important in the general performance of the structure. Pavement designs in these

  16. Multiscale Phenomena in the Solid-Liquid Transition State of a Granular Material

    Science.gov (United States)

    2011-11-29

    SECURITY CLASSIFICATION OF: This project, with Antoinette Tordesillas of U of Melbourne, investigated models for the upper soil surface and its response to...chains in dense granular assemblies: physical and numerical experiments, Geomechanics and Geoengineering, (03 2009): 0. doi: 10.1080

  17. Anomalous energy cascades in dense granular materials yielding under simple shear deformations

    NARCIS (Netherlands)

    Saitoh, K.; Mizuno, Hideyuki

    2015-01-01

    By using molecular dynamics (MD) simulations of dense granular particles in two dimensions, we study turbulent-like structures of their non-affine velocities under simple shear deformations. We find that the spectrum of non-affine velocities, introduced as an analog of energy spectrum for turbulent

  18. Enhancement of the bentonite sorption properties.

    Science.gov (United States)

    Mockovciaková, Annamária; Orolínová, Zuzana; Skvarla, Jirí

    2010-08-15

    The almost monomineral fraction of bentonite rock-montmorillonite was modified by magnetic particles to enhance its sorption properties. The method of clay modification consists in the precipitation of magnetic nanoparticles, often used in preparing of ferrofluids, on the surface of clay. The influence of the synthesis temperature (20 and 85 degrees C) and the weight ratio of bentonite/iron oxides (1:1 and 5:1) on the composite materials properties were investigated. The obtained materials were characterized by the X-ray diffraction method and Mössbauer spectroscopy. Changes in the surface and pore properties of the magnetic composites were studied by the low nitrogen adsorption method and the electrokinetic measurements. The natural bentonite and magnetic composites were used in sorption experiments. The sorption of toxic metals (zinc, cadmium and nickel) from the model solutions was well described by the linearized Langmuir and Freundlich sorption model. The results show that the magnetic bentonite is better sorbent than the unmodified bentonite if the initial concentration of studied metals is very low. Copyright 2010 Elsevier B.V. All rights reserved.

  19. 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

  20. 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

  1. 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)

  2. Numerical study of the flow of granular materials down an inclined plane. Quarterly report, October 1, 1993--February 28, 1994

    Energy Technology Data Exchange (ETDEWEB)

    Rajagopal, K.R.

    1994-05-01

    In the previous report the governing equations for the flow of granular materials down an inclined plane, modeled by the constitutive theory proposed by Boyle and Massoudi (1990) were derived. These equations are solved numerically subject to the appropriate boundary conditions. The effect of various non-dimensional parameters on the volume fraction and velocity are presented in the form of graphs. In this report we derive the governing equations for the flow of granular materials down an inclined plane using the continuum model proposed by Rajagopal and Massoudi [cf. Goodman and Cowin (1971, 1972), Rajagopal and Massoudi (1990)]. Here, we study the effect of the various forms of the materials parameters ({Beta}`s) as discussed in Case I, II, and III in the following sections. The numerical solutions for case I and case II were presented in the earlier reports and case III are presented in the form of graphs for various nondimensional parameters. Also, the solutions from Case I, II, and III are compared to see how the structure of the material parameters affect the velocity, volume fraction and temperature fields.

  3. Effect of packing fraction on shear band formation in a granular material forced by a penetrometer.

    Science.gov (United States)

    Tapia, Franco; Espíndola, David; Hamm, Eugenio; Melo, Francisco

    2013-01-01

    Granular ensembles subjected to confinement forces can reach metastable states that often break down via formation of shear bands for sufficiently high deviatoric stress. In this article we investigate the flow induced in a granular ensemble that is perturbed by a vertically moving finger in a quasiplanar geometry. The flow exhibits spiral-like shear bands and evolves discontinuously in time, in concert with an oscillating penetration force. We characterize the nature of this nucleation-relaxation type process for loose to dense packing fractions. The nucleation dynamics is reasonably well described by a simple Mohr-Coulomb failure criterium in which the friction coefficient is a function of packing fraction. We contrast our findings with the recent work of Gravish et al. [Phys. Rev. Lett. 105, 128301 (2010)].

  4. Experimental and Simulation Results for the Impact of a Rotating Flexible Link with a Granular Material

    Directory of Open Access Journals (Sweden)

    Dan Marghitu

    2014-03-01

    Full Text Available In this paper, a rotating flexible link impacting a granular media is studied. The influences of initial impact velocity and impact angle are examined. The resistance forces are expressed as the sum of a dynamic frictional force (velocity-dependent and a static resistance force (depth dependent. The penetrating angle increases with initial impact velocity as expected. However, the stopping time decreases with initial impact velocity for all initial impact angles for the considered system.

  5. Modeling interface shear behavior of granular materials using micro-polar continuum approach

    Science.gov (United States)

    Ebrahimian, Babak; Noorzad, Ali; Alsaleh, Mustafa I.

    2018-01-01

    Recently, the authors have focused on the shear behavior of interface between granular soil body and very rough surface of moving bounding structure. For this purpose, they have used finite element method and a micro-polar elasto-plastic continuum model. They have shown that the boundary conditions assumed along the interface have strong influences on the soil behavior. While in the previous studies, only very rough bounding interfaces have been taken into account, the present investigation focuses on the rough, medium rough and relatively smooth interfaces. In this regard, plane monotonic shearing of an infinite extended narrow granular soil layer is simulated under constant vertical pressure and free dilatancy. The soil layer is located between two parallel rigid boundaries of different surface roughness values. Particular attention is paid to the effect of surface roughness of top and bottom boundaries on the shear behavior of granular soil layer. It is shown that the interaction between roughness of bounding structure surface and the rotation resistance of bounding grains can be modeled in a reasonable manner through considered Cosserat boundary conditions. The influence of surface roughness is investigated on the soil shear strength mobilized along the interface as well as on the location and evolution of shear localization formed within the layer. The obtained numerical results have been qualitatively compared with experimental observations as well as DEM simulations, and acceptable agreement is shown.

  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. 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.)

  8. 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

  9. 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)

  10. 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.

  11. 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.

  12. 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

  13. Bentonite mat demonstration. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Serrato, M.G.

    1994-12-30

    The Bentonite Mat Demonstration was developed to provide the Environmental Restoration Department with field performance characteristics and engineering data for an alternative closure cover system configuration. The demonstration was initiated in response to regulatory concerns regarding the use of an alternative cover system for future design configurations. These design considerations are in lieu of the US Environmental Protection Agency (EPA) Recommended Design for Closure Cover Systems and specifically a single compacted kaolin clay layer with a hydraulic conductivity of 1 {times} 10{sup {minus}7} cm/sec. This alternative configuration is a composite geosynthetic material hydraulic barrier consisting from bottom to top: 2 ft compacted sandy clay layer (typical local Savannah River Site soil type) that is covered by a bentonite mat--geosynthetic clay liner (GCL) and is overlaid by a 40 mil High Density Polyethylene (HDPE) geomembrane--flexible membrane liner. This effort was undertaken to obtain and document the necessary field performance/engineering data for future designs and meet regulatory technical requirements for an alternative cover system configuration. The composite geosynthetic materials hydraulic barrier is the recommended alternative cover system configuration for containment of hazardous and low level radiological waste layers that have a high potential of subsidence to be used at the Savannah River Site (SRS). This alternative configuration mitigates subsidence effects in providing a flexible, lightweight cover system to maintain the integrity of the closure. The composite geosynthetic materials hydraulic barrier is recommended for the Sanitary Landfill and Low Level Radiological Waste Disposal Facility (LLRWDF) Closures.

  14. 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.

  15. 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

  16. Scaling laws for the mechanics of loose and cohesive granular materials based on Baxter's sticky hard spheres.

    Science.gov (United States)

    Gaume, Johan; Löwe, Henning; Tan, Shurun; Tsang, Leung

    2017-09-01

    We have conducted discrete element simulations (pfc3d) of very loose, cohesive, granular assemblies with initial configurations which are drawn from Baxter's sticky hard sphere (SHS) ensemble. The SHS model is employed as a promising auxiliary means to independently control the coordination number z_{c} of cohesive contacts and particle volume fraction ϕ of the initial states. We focus on discerning the role of z_{c} and ϕ for the elastic modulus, failure strength, and the plastic consolidation line under quasistatic, uniaxial compression. We find scaling behavior of the modulus and the strength, which both scale with the cohesive contact density ν_{c}=z_{c}ϕ of the initial state according to a power law. In contrast, the behavior of the plastic consolidation curve is shown to be independent of the initial conditions. Our results show the primary control of the initial contact density on the mechanics of cohesive granular materials for small deformations, which can be conveniently, but not exclusively explored within the SHS-based assembling procedure.

  17. 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).

  18. 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...

  19. 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.

  20. 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

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Granular flows : fluidization and anisotropy

    NARCIS (Netherlands)

    Wortel, Gerrit Herman

    2014-01-01

    This work discusses the flow of granular materials (e.g. sand). Even though a single particle is a simple object, the collective behavior of billions of particles can be very complex. In a surprisingly large amount of cases, it is not exactly known how a granular material behaves, and this while

  7. 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.

  8. 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.

  9. Theoretical studies on the mechanical behavior of granular materials under very low intergranular stresses

    Science.gov (United States)

    French, Kenneth W., Jr.

    1986-01-01

    The salient aspects of the theoretical modeling of a conventional triaxial test (CTC) of a cohesionless granular medium with stress and strain rate loading are described. Included are a controllable gravitational body force and provision for low confining pressure and/or very low intergranular stress. The modeling includes rational, analytic, and numerical phases, all in various stages of development. The numerical evolutions of theoretical models will be used in final design stages and in the analysis of the experimental data. In this the experimental design stage, it is of special interest to include in the candidate considerations every anomaly found in preliminary terrestrial experimentation. Most of the anomalies will be eliminated by design or enhanced for measurement as the project progresses. The main aspect of design being not the physical apparatus but the type and trajectories of loading elected. The major considerations that have been treated are: appearance and growth of local surface aberrations, stress-power coefficients, strain types, optical strain, radial bead migration, and measures of rotation for the proper stress flux.

  10. 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.

  11. 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.

  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.

    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)

  13. Temperature influence on structural changes of foundry bentonites

    Science.gov (United States)

    Holtzer, Mariusz; Bobrowski, Artur; Żymankowska-Kumon, Sylwia

    2011-10-01

    The results of investigations of three calcium bentonites, activated by sodium carbonate, applied in the foundry industry as binding material for moulding sands, subjected to the influence of high temperatures - are presented in the paper. Investigations were performed by the thermal analysis (TG) method, the infrared spectroscopy (FTIR) method and the modern Cu(II)-TET complex method (used for the determination of the montmorillonite content in bentonite samples). The occurrence of the dehydration process and two-stage dehydroxylation process was confirmed only for bentonite no. 2. This probably indicates that cis- and trans-isomers are present in the octahedric bentonite structure. Tests were performed at temperatures: 500, 550, 700, 900, 1000, 1100, 1200 °C.

  14. 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.)

  15. 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.

  16. 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.

  17. 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

  18. 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.

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

    Science.gov (United States)

    Duan, Luanfang; Qi, Chonggang; Ling, Xiang; Peng, Hao

    2018-03-01

    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%.

  20. Mechanical Properties of Plastic Concrete Containing Bentonite

    OpenAIRE

    Peng Zhang; Qiaoyan Guan; Qingfu Li

    2013-01-01

    Plastic concrete consists of aggregates, cement, water and bentonite, mixed at a high water cement ratio, to produce a ductile material. It is used for creating an impermeable barrier (cut-off wall) for containment of contaminated sites or seepage control in highly permeable dam foundations. The effects of water to binder ratio and clay dosage on mechanical properties of plastic concrete were investigated. The results indicate that the water to binder ratio and clay dosage have great influenc...

  1. A grain-scale study of unsaturated flow in highly swelling granular materials

    NARCIS (Netherlands)

    Sweijen, Thomas|info:eu-repo/dai/nl/369415191

    2017-01-01

    Unsaturated flow in swelling porous materials are common and important phenomena in industrial products and earth materials; for example, in paper, hygienic products, swelling clays, and foods. Swelling causes porous media to expand and to deform, which results in a change in pore structure and thus

  2. Numerical study of one-dimensional compression of granular materials. I. Stress-strain behavior, microstructure, and irreversibility

    Science.gov (United States)

    Khalili, Mohamed Hassan; Roux, Jean-Noël; Pereira, Jean-Michel; Brisard, Sébastien; Bornert, Michel

    2017-03-01

    The behavior of a model granular material, made of slightly polydisperse beads with Hertz-Mindlin elastic-frictional contacts, in oedometric compression (i.e., compression along one axis, with no lateral strain) is studied by grain-level numerical simulations. We systematically investigate the influence of the (idealized) packing process on the microstructure and stresses in the initial, weakly confined equilibrium state, and prepare both isotropic and anisotropic configurations differing in solid fraction Φ and coordination number z . Φ (ranging from maximally dense to moderately loose), z (which might vary independently of Φ in dense systems), fabric and force anisotropy parameters, and the ratio K0 of lateral stresses σ2=σ3 to stress σ1 in the compression direction are monitored in oedometric compression in which σ1 varies by more than three orders of magnitude. K0 reflects the anisotropy of the assembling process and may remain nearly constant in further loading if the material is already oedometrically compressed (as a granular gas) in the preparation stage. Otherwise, it tends to decrease steadily over the investigated stress range. It is related to force and fabric anisotropy parameters by a simple formula. Elastic moduli, separately computed with an appropriate matrix method, may express the response to very small stress increments about the transversely isotropic well-equilibrated states along the loading path, although oedometric compression proves an essentially anelastic process, mainly due to friction mobilization, with large irreversible effects apparent upon unloading. While the evolution of axial strain ɛ1 and solid fraction Φ (or of the void ratio e =-1 +1 /Φ ) with axial stress σ1 is very nearly reversible, especially in dense samples, z is observed to decrease (as previously observed in isotropic compression) after a compression cycle if its initial value was high. K0 relates to the evolution of internal variables and may exceed 1 in

  3. 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)

  4. 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)

  5. Lot A2 test, THC modelling of the bentonite buffer

    Science.gov (United States)

    Itälä, Aku; Olin, Markus; Lehikoinen, Jarmo

    Finnish spent nuclear fuel is planned to be disposed of deep in the crystalline bedrock of the Olkiluoto island. In such a repository, the role of the bentonite buffer is considered to be central. The initially unsaturated bentonite emplaced around a spent-fuel canister will become fully saturated by the groundwater from the host rock. In order to assess the long-term safety of a deep repository, it is essential to determine how temperature influences the chemical stability of bentonite. The aim of this study was to achieve an improved understanding of the factors governing the thermo-hydro-chemical evolution of the bentonite buffer subject to heat generation from the disposed fuel and in contact with a highly permeable rock fracture intersecting a canister deposition hole. TOUGHREACT was used to model a test known as the long-term test of buffer material adverse-2, which was conducted at the Äspö hard rock laboratory in Sweden. The results on the evolution of cation-exchange equilibria, bentonite porewater chemistry, mineralogy, and saturation of the buffer are presented and discussed. The calculated model results show similarity to the experimental results. In particular, the spatial differences in the saturation and porewater chemistry of the bentonite buffer were clearly visible in the model.

  6. 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.

  7. 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

  8. 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.

  9. 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...

  10. Segregation of Granular Material in Two and Three-Dimensional Units

    Indian Academy of Sciences (India)

    Segregation of particulate materials in mixtures is controlledby differences in density, shape, and size. Experiments on segregationwere performed in two and three-dimensional demonstrationunits. The results conclusively indicated that the segregationof solids is affected by the shape, size and density ofgranular particles.

  11. Grain-scale modelling of swelling granular materials; application to super absorbent polymers

    NARCIS (Netherlands)

    Sweijen, T.; Chareyre, B.; Hassanizadeh, S.M.; Karadimitriou, N.K.

    Swelling is an important process in many natural materials and industrial products, such as swelling clays, paper, and Super Absorbent Polymer (SAP) particles in hygienic products. SAP particles are capable to absorb large amounts of fluid. Each grain of SAP can absorb water 30 to 1000 times its

  12. 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.

  13. 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

  14. Brittle to ductile transition in a model of sheared granular materials

    Science.gov (United States)

    Ma, X.; Elbanna, A. E.

    2016-12-01

    Understanding the fundamental mechanisms of deformation and failure in sheared fault gouge is critical for the development of physics-based earthquake rupture simulations that are becoming an essential ingredient in next generation hazard and risk models. To that end, we use the shear transformation zone (STZ) theory, a non-equilibrium statistical thermodynamics framework to describe viscoplastic deformation and localization in gouge materials as a first step towards developing multiscale models for earthquake source processes that are informed by high-resolution fault zone physics. The primary ingredient of the STZ theory is that inelastic deformation occurs at rare and local non-interacting soft zones known as the shear transformation zones. The larger the number of these STZs the more disordered (the more loose) the layer is. We will describe an implementation of this theory in a 2D/3D finite element framework, accounting for finite deformation, under both axial and shear loading and for dry and saturated conditions. We examine conditions under which a localized shear band may form and show that the initial value of disorder (or the initial porosity) plays an important role. In particular, our simulations suggest that if the material is more compact initially, the behavior is more brittle and the plastic deformation localizes with generating large strength drop. On the other hand, an initially loose material will show a more ductile response and the plastic deformations will be distributed more broadly. We will further show that incorporation of pore fluids alters the localization pattern and changes the stress slip response due to coupling between gouge volume changes (compaction and dilation) and pore pressure build up. We validate the model predictions by comparing them to available experimental observations on strain localization and fault gouge strength evolution. Finally, we discuss the implications of our model for gouge friction and dynamic weakening.

  15. Educational Brief: Using Space for a Better Foundation on Earth Mechanics of Granular Materials

    Science.gov (United States)

    Dooling, Dave (Editor)

    2002-01-01

    Soils are three-phase composite materials that consist of soil, solid particles, and voids filled with water and/or air. Based on the particle-size distribution, they are generally classified as fine-grained (clays and plastic silts) and coarse-grained soils (nonplastic silts, sand, and gravel). Soil's resistance to external loadings is mainly derived from friction between particles and cohesion. Friction resistance is due to particles' surface-to-surface friction, interlocking, crushing, rearrangement, and dilation (or expansion) during shearing. Cohesion can be due to chemical cementation between particles, electrostatic and electromagnetic forces, and soil-water reaction and equilibrium. The basic factor responsible for the strength of coarse-grained soils is friction. Cohesion can be ignored. This educational brief focuses on measuring shear strength of sands (typical example of coarse-grained soils) where, for the same material, packing density is a main factor to be considered when one asks about the shear strength value. As the external load is applied, the soil's resistance is attained through shearing resistance, which causes the soil volume to increase (expand) or decrease (compress) depending on the initial packing density.

  16. Experimental investigation of impinging jet erosion on model cohesive granular materials

    Directory of Open Access Journals (Sweden)

    Brunier-Coulin Florian

    2017-01-01

    Full Text Available Erosion of soils affects both natural landscapes and engineering constructions as embankment dams or levees. Improving the safety of such earthen structures requires in particular finding out more about the elementary mechanisms involved in soil erosion. Towards this end, an experimental work was undertaken in three steps. First, several model materials were developed, made of grains (mostly glass beads with solid bridges at particle contacts whose mechanical yield strength can be continuously varied. Furthermore, for most of them, we succeeded in obtaining a translucent system for the purpose of direct visualization. Second, these materials were tested against surface erosion by an impinging jet to determine a critical shear stress and a kinetic coefficient [2, 3]. Note that an adapted device based on optical techniques (combination of Refractive Index Matching and Planar Laser Induced Fluorescence [3] was used specifically for the transparent media. Third, some specifically developed mechanical tests, and particularly traction tests, were implemented to estimate the mechanical strength of the solid bridges both at micro-scale (single contact and at macro-scale (sample and to investigate a supposed relationship with soil resistance to erosion.

  17. Micromechanical formulation of the mobilized stress ratio under principal stress rotation in granular materials

    Science.gov (United States)

    Shaverdi, Homayoun; Kalantary, Farzin; Taha, Mohd R.

    2017-06-01

    In this paper the mobilized stress ratio is investigated by using the static equilibrium at the micro scale level analysis. The mobilized stress ratio is obtained in the distribution of the contact normal, E(β), and the inter-particle mobilized friction angle, ϕμ . The second invariant of the fabric tensor, α is used to account for fabric and its evolution. There is a difference between the theoretical rotation of principal stress axes that is obtained by the classical equations of the mechanics of materials and the experimental rotation of principal stress axes. The experimental rotation is related to the anisotropic parameter, α. The noncoincidence between the theoretical and experimental is related to the relative direction of the mobilized plane and the bedding plane. A comparison with experimental tests demonstrates the validity of this formulation.

  18. Micromechanical formulation of the mobilized stress ratio under principal stress rotation in granular materials

    Directory of Open Access Journals (Sweden)

    Shaverdi Homayoun

    2017-01-01

    Full Text Available In this paper the mobilized stress ratio is investigated by using the static equilibrium at the micro scale level analysis. The mobilized stress ratio is obtained in the distribution of the contact normal, E(β, and the inter-particle mobilized friction angle, ϕμ . The second invariant of the fabric tensor, α is used to account for fabric and its evolution. There is a difference between the theoretical rotation of principal stress axes that is obtained by the classical equations of the mechanics of materials and the experimental rotation of principal stress axes. The experimental rotation is related to the anisotropic parameter, α. The noncoincidence between the theoretical and experimental is related to the relative direction of the mobilized plane and the bedding plane. A comparison with experimental tests demonstrates the validity of this formulation.

  19. Hybrid Alkaline Cements: Bentonite-Opc Binders

    Directory of Open Access Journals (Sweden)

    Ines Garcia-Lodeiro

    2018-03-01

    Full Text Available Moderately alkaline activators can be used to formulate cementitious binders with a high Supplemetary Cementitious Materials (SCMs and a low portland cement content (hybrid alkaline cements. This study aimed to prepare hybrid alkaline cements containing large percentages of dehydroxylated bentonite (BT and small Portland cement (OPC fractions, with 5% Na2SO4 as a solid alkaline activator. The hydration kinetics of the pastes hydrated in water in the presence and absence of the solid activator were assessed by isothermal conduction calorimetry, whilst the reaction products were characterised with X-Ray Powder Diffraction (XRD and Fourier-transform Infrared Spectroscopy (FTIR. The presence of the alkaline activator hastened OPC and BT/OPC hydration: more heat of hydration was released, favouring greater initial bentonite reactivity. The portlandite forming during cement hydration reacted readily with the Na2SO4, raising medium alkalinity and enhancing bentonite dissolution and with it reaction product precipitation (primarily (N,C-A-S-H-like gels that co-exist with C-S-H- or C-A-S-H-like gels. The presence of sulfate ions favoured the formation of AFm-like phases. Preceding aspects accelerated the hydration reactions, with the formation of more reaction product and matrix densification. As a result, the 28 days Na2SO4 activated systems developed greater mechanical strength than the water-hydrated systems, with the 60% BT/40% OPC blends exhibiting higher compressive strength than the 100% OPC pastes.

  20. 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.

  1. 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

  2. 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.

  3. 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)

  4. 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)

  5. Micromechanics of granular materials

    National Research Council Canada - National Science Library

    Cambou, Bernard; Jean, Michel; Radjai, Farhang

    2009-01-01

    ... . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2.2. Contact network anisotropy: fabric tensors . . . . . . . . . . . . . 1.2.2.1. General case . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2.2.2...

  6. 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)

  7. 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

  8. 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

  9. Preparation, characterization and thermal stability of bentonite modified with bis-imidazolium salts

    Energy Technology Data Exchange (ETDEWEB)

    Makhoukhi, B., E-mail: benamarmakh@yahoo.fr [Laboratory of Separation and Purification Technologies, Department of Chemistry, Tlemcen University, Box 119, Tlemcen (Algeria); Villemin, D. [Laboratoire de Chimie Moléculaire et Thio-organique, UMR CNRS 6507, INC3M, FR 3038, ENSICAEN and Université de Caen, 14050 Caen (France); Didi, M.A. [Laboratory of Separation and Purification Technologies, Department of Chemistry, Tlemcen University, Box 119, Tlemcen (Algeria)

    2013-02-15

    Sodium bentonite was modified with several organic bis-imidazolium salts. Organoclays with water soluble surfactants were prepared by the traditional cation exchange reaction. The bis-imidazolium-bentonites were characterized by Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction analysis (PXRD) and thermogravimetric analysis (TGA). The effect of chemical composition and molecular weight of the salts on the thermal stability and basal spacing were evaluated. The bis-imidazolium-bentonites showed enhanced thermal stability (300–400 °C) and may be potentially useful materials for melt processing of polymer/layered silicates nanocomposites. - Highlights: ► Geometry and volume of the molecule influence on interlayer spacing of modified bentonites. ► The intercalation increases with molecule length. ► The modified bentonites have an appreciably higher thermal stability.

  10. 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

  11. 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.

  12. 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

  13. Physico-chemical characterization of bentonite and its application for Mn2+ removal from water

    Directory of Open Access Journals (Sweden)

    Ranđelović Marjan S.

    2011-01-01

    Full Text Available Bentonite is mainly composed of clay minerals from smectite group, therefore it has a well developed and chemically active surface area and high cation exchange capacity. Moreover, an interlayer space of smectite has unusual hydration properties, which manifest as swelling of bentonite in water. These properties make bentonite as a commonly used raw material in chemistry and industry, and it is very important in environmental protection and water treatment as an effective sorbent of heavy metals. The results of X-ray diffraction, a cationic exchange capacity, specific surface area, acid-base properties of the surface and the swelling index showed that the bentonite sample contains mostly montmorillonite. The aim of this study was to test the efficacy of bentonite in the removal of Mn2+ from aqueous systems. The experimental results of Mn2+ adsorption on the bentonite were interpreted by Langmuir, Freundlich and Dubinin-Radushkevich adsorption isotherms. The adsorption isotherm studies indicate that the adsorption of Mn2+ follows Langmuir isotherm very well. Theoretical monolayer saturation capacity according to Langmuir model was 12.41 mg/g. The removal of Mn2+ is achieved by ion exchange mechanism with naturally occurring cations in bentonite, as well as by forming the inner- and outer-sphere complexes with bentonite surface.

  14. 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

  15. 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.

  16. Coupled thermo-hydro-chemical models of swelling bentonites

    Science.gov (United States)

    Samper, Javier; Mon, Alba; Zheng, Liange; Montenegro, Luis; Naves, Acacia; Pisani, Bruno

    2014-05-01

    The disposal of radioactive waste in deep geological repositories is based on the multibarrier concept of retention of the waste by a combination of engineered and geological barriers. The engineered barrier system (EBS) includes the solid conditioned waste-form, the waste container, the buffer made of materials such as clay, grout or crushed rock that separate the waste package from the host rock and the tunnel linings and supports. The geological barrier supports the engineered system and provides stability over the long term during which time radioactive decay reduces the levels of radioactivity. The strong interplays among thermal (T), hydrodynamic (H), mechanical (M) and chemical (C) processes during the hydration, thermal and solute transport stages of the engineered barrier system (EBS) of a radioactive waste repository call for coupled THMC models for the metallic overpack, the unsaturated compacted bentonite and the concrete liner. Conceptual and numerical coupled THMC models of the EBS have been developed, which have been implemented in INVERSE-FADES-CORE. Chemical reactions are coupled to the hydrodynamic processes through chemical osmosis (C-H coupling) while bentonite swelling affects solute transport via changes in bentonite porosity changes (M-H coupling). Here we present THMC models of heating and hydration laboratory experiments performed by CIEMAT (Madrid, Spain) on compacted FEBEX bentonite and numerical models for the long-term evolution of the EBS for 1 Ma. The changes in porosity caused by swelling are more important than those produced by the chemical reactions during the early evolution of the EBS (t iron mineral phases (corrosion products) released by the corrosion of the carbon steel canister; and 2) The hyper alkaline plume produced by the concrete liner. Numerical results show that the pH in the bentonite pore water in the presence of a concrete liner can vary from neutral to up to 13 over a time scale of 1 Ma although dissolution of

  17. 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.

  18. Migration Behaviour of Strontium in Czech Bentonite Clay

    OpenAIRE

    Lucie Baborova; Dušan Vopálka; Eva Hofmanová; Aleš Vetešník

    2016-01-01

    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 th...

  19. 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)

  20. 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

  1. Multiscale Phenomena in the Solid-Liquid Transition State of a Granular Material: Analysis, Modeling and Experimentation

    Science.gov (United States)

    2010-11-21

    Methods in Geomechanics 33 pp 1737-1768. Tordesillas, A, Shi, J and Muhlhaus, H (2009) “Non-coaxiality and force chain evolution” International...Buckling force chains in dense granular assemblies: physical and numerical experiments” Geomechanics and Geoengineering 4(1) pp 3-16. Tordesillas, A...J, Tshaikiwsky, T (2010) “Stress-dilatancy and force chain evolution”, International Journal of Numerical and Analytical Methods in Geomechanics DOI

  2. 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...

  3. 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 ...

  4. Physico-chemistry of continental Bentonites and Kaolin for ceramic ...

    African Journals Online (AJOL)

    Growing demand for bentonite and kaolin applications in the ceramic industry motivated this study which aimed at physico-chemically characterizing some selected continental clayey materials from Botswana, Mozambique, Pakistan, Senegal, South Africa and the United States of America. The hydrogen ion concentration ...

  5. Artificial wetting of buffer material. Small scale

    International Nuclear Information System (INIS)

    Holt, E.; Marjavaara, P.; Loeija, M.

    2011-07-01

    The purpose of this work was to investigate the swelling behaviour of artificially wetted highly compacted bentonite buffer blocks used in deposition holes for nuclear waste containment. The target was to make a preliminary study if homogeneous and rapid swelling of the bentonite is possible to achieve in the gap between the buffer and the rock wall of the deposition hole by artificial wetting. It is expected that the thermal, mechanical, chemical and hydraulic properties of the whole deposition system are better when the bentonite-rock gap is closed. In practice it is desirable that the bentonite material has a volume increase sufficient enough to create pressure against the rock surface. Uniform bentonite buffer swelling into the gap would prevent rock scaling while lowering the risks of bentonite piping and erosion due to potential water flow. In this work, two preliminary sets of tests were done on bentonite block swelling and water filtration through pellets. The majority of work was within the primary tests, where bentonite blocks were confined in a test chamber and swelling was induced by artificial wetting. Water was poured directly into the gap from the top, without the aid of pipes or pressure. After the initial watering, no additional water or moisture was made available for the system during the test duration. The resulting bentonite swelling pressure in both the radial and vertical directions was measured over time. 13 different test scenarios were investigated, including: varying block size of 10 cm height disks or 30 cm blocks, eccentric aligned blocks with gap sizes of 5 and 45 mm, gap sizes of 25 mm or 50 mm, using gap filling with pellets or granular in combined with water, free upward swelling or confinement, addition of water at varying rates, and longer term test duration. In some cases, video images were taken during the swelling, to get an indication of the time until the gap was sealed. After the wetting tests, material properties of the

  6. 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.

  7. 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)

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

    OpenAIRE

    Robert Ronal Widjaya; Nino Rinaldi; Bambang Soegijono

    2012-01-01

    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 co...

  9. 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.

  10. Review of Suction Water Content Relationship of Bentonite-Sand Mixtures Considering Temperature Effects

    Science.gov (United States)

    Rawat, Abhishek; Zhi Lang, Lin; Baille, Wiebke

    2015-04-01

    Bentonite-sand mixture is one of the candidate sealing/ buffer material for landfills, hazardous and high level radioactive waste repository. The long term satisfactory performance of bentonite sand mixture in terms of load bearing function, sealing function and buffer function is governed by hydro-mechanical response of material under elevated temperature conditions. The suction-water content relationship is one of the key parameter, which govern the thermo-hydro-mechanical behavior of compacted bentonite-sand mixture. This paper presents brief review of suction water content relationships of bentonite-sand mixture considering temperature effects. Numerous parametric models or equations have been developed for representing the soil water characteristics curve i.e. SWCC for isothermal conditions. The most frequently used equations for representing the SWCC are the van Genuchten (1980) and Fredlund and Xing (1994) SWCC equations. Various researchers (Romero et al. 2000; Villar and Lloret, 2004; Tang and Cui, 2005; Agus, 2005; Arifin, 2008) have reported the temperature effect on the water retention behavior of compacted bentonite-sand mixtures. The testing program, results and major conclusions made by above mentioned researchers were discussed in this paper. The changes in hydro-mechanical behavior due to elevated temperature are also discussed based on the suction components of soil which are influenced by temperature. As a general conclusion, total suction of the bentonite-sand mixtures is a function of mixture water content and mixture bentonite content or collectively a function of bentonite water content both at room temperature and at elevated temperature. At a constant temperature, different techniques for measuring suction results in different values of suction depending on accuracy of the sensor and calibration technique used as founded earlier by Agus (2005). The change in total suction due to change in temperature lower than 100 degree C is reversible

  11. 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)

  12. 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.

  13. 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.

  14. 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.)

  15. Identification and Purification of Montmorillonite Mineral of Ghaen Mine Bentonite

    Directory of Open Access Journals (Sweden)

    P. Mirhoseini Moosavi

    2015-06-01

    Full Text Available Montmorillonite is the major mineral of Bentonite with many applications in industrial fields but some impurities decreases the quality of the bentonite. The main objective of this study was to investigate the suitable method for purification of Ghaen mine bentonite. A combination of methods was considered including wet sieving and sedimentation, centrifuge and ultrasound. The efficiency of purification methods was determined based on X-ray, particle size, cation exchange capacity (CEC and ratio peak of the Quartz/Montmorillonite analysis before and after experiments. The results showed that such methods were efficient for preparing of the materials having high quantity of montmorillonite with less than 2 microns particle sizes. Cristobalite was the only mineral remained in samples, however many of particles were exempted from the samples. Cristobalite was the main impurity remained with montmorillonite. Chemical treatment is the only way for its complete removal. The results of this study revealed that by using easy, cheap and fast methods, it is possible for acceptable purification of bentonite.

  16. 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.

  17. 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)

  18. Influence of temperature on the water retention properties of compacted GMZ01 bentonite

    OpenAIRE

    WAN, Min; YE, Wei-Min; CHEN, Yong-Gui; CUI, Yu-Jun; WANG, Ju

    2015-01-01

    Investigation of the temperature effects on the water retention properties of compacted bentonite is of great importance in the context of geological disposal of high-level radioactive waste (HLW) based on the multi-barrier concept. Gaomiaozi (GMZ) bentonite, collected from the Inner Mongolia Autonomous Region of China, has been selected as a potential buffer/backfill material for the construction of Chinese HLW deep geological repository. In this study, soil water retention curves (SWRCs) of...

  19. The influence of temperature and hydration on the sorption properties of bentonite.

    Science.gov (United States)

    Vinsová, Hana; Jedináková-Krízová, Vera; Kolaríková, Irena; Adamcová, Jana; Prikryl, Richard; Zeman, Josef

    2008-02-01

    The effects of exposure to synthetic groundwater at elevated temperature gradients on the sorption properties of bentonite were investigated using the Mock-Up-Cz experiment. This experiment simulated the vertical placement of a container of radioactive waste according to the Swedish KBS-3 system for a period of more than 3 years. The mineralogical composition, as well as its chemical and physico-chemical properties, including the uptake of (99)TcO(4)(-) and (134)Cs(+), was used to evaluate the chemical changes caused by the long-term exposure of bentonite buffer to thermal and hydration gradients. It was found that the bentonite material was predominantly stable. No more than 2% of the montmorillonite was transformed due to thermal and moisture gradients. It was concluded that the new-formed mineral phases have no significant influence on the ion exchange and sorption properties of bulk bentonite samples.

  20. 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)

  1. 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

  2. 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

  3. Consequences of loss or missing bentonite in a deposition hole. A theoretical study

    International Nuclear Information System (INIS)

    Boergesson, Lennart; Hernelind, Jan

    2006-08-01

    The swelling properties of bentonite make the buffer material swell and close open gaps or channels to form a more homogeneous buffer. These properties are important not only for homogenising the buffer after installation of the bentonite blocks but also after long time if openings in the buffer would appear. However, the swelling and sealing of bentonite cannot take place unhindered since there is a resistance to swelling caused by friction both internally in the bentonite and between the bentonite and the surrounding fixed walls represented by the rock surface and the canister. In order to investigate how well the buffer material seals openings resulting from different processes, a number of finite element calculations have been performed. The finite element code ABAQUS was used for the calculations. The bentonite has been modelled as completely water saturated. The mechanical properties of the buffer controlling the swelling and consolidation phase are based on the models and properties derived for MX-80. 1) One of the investigated scenarios concerns either huge loss of bentonite after extremely long time of erosion or the improbable case of one to three missing bentonite rings at the upper end of the canister. The rings are 50 cm thick and 1-3 of them are assumed to be forgotten during the installation of the buffer. This case can thus also represent an extreme loss of bentonite by erosion or bentonite dispersion and subsequent colloid transportation after fresh water intrusion (corresponds to 1,200-3,600 kg dry mass). The results show that when large amounts of bentonite are lost or missing from start the bentonite swells and fills the empty space but the density and resulting swelling pressure are rather low due to the friction in the buffer and the friction against the rock surface. For 50 cm opening the swelling pressure is in average 0.5-1.0 MPa in almost the entire former hole. However, if the rock surface is smooth and the resulting friction against the

  4. Granular media : flow & agitations

    NARCIS (Netherlands)

    Dijksman, Joshua Albert

    2009-01-01

    This thesis is about weakly driven granular flows and suspensions. Chapter 1 is an overview of the current knowledge of slow granular flows in so-called split-bottom geometries, which in essence consist of a disk rotating at the bottom of a container. In chapter 2 we study dry granular flows in this

  5. Study of corrosion behaviour in saturated bentonite barrier Corroben

    International Nuclear Information System (INIS)

    Azkarate, I.; Insausti, M.; Medina, V.

    2004-01-01

    The corrosion behavior in saturated bentonite of various candidate metallic materials, to be used in the fabrication of containers of high level radioactive waste granite repositories, has been studied in this project. Due to the multi-barrier concept in which the canisters are surrounded by a clay barrier of compacted bentonite blocks, special attention has been paid to the characterization of corrosion products and the interaction between these and the repository sealing bentonite. The following metallic materials have been studied: S355 carbon steel, AISI 316L stainless steel, Cu-ETP electrolytic copper and Cu30Ni alloy. Samples of the alloys have been embedded in saturated bentonite to a water content of 25%, and compacted. The obtained pastilles have been introduced in autoclaves and tested at different temperatures and times ranging from one to 18 months. Once tests have concluded, several parameters have been evaluated: corrosion morphology, general corrosion rates calculated by gravimetric methods, nature and composition of the corrosion products and penetration of the corrosion products into the bentonite. Experimental data obtained are used to developed models of the corrosion behavior of canisters under disposal conditions. Results show that S355 carbon steel has suffered the highest general corrosion attack, with average corrosion rates of 10 per year and maximum penetration of 100 measured in specimens tested at 75C during 18 months. The most common analyzed corrosion product has been siderite, FeCO3. Formation of siderite, in the test conditions, effectively passivated the steel because of its stable and adherent feature. In test carried out at 25 and 5 C, sulfur rich corrosion products are observed, thus indicating a microbiologically corrosion phenomena due to the metabolic activity of bacteria present in the bentonite. No appreciable general corrosion rates, nor sensitivity to localized corrosion, has been observed in the AISI 316L stainless steel

  6. 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...

  7. Investigation of particle properties on the holding force in a granular gripper

    NARCIS (Netherlands)

    Meuleman, Steven; Balt, Vincent; Jarray, Ahmed; Magnanimo, Vanessa

    The granular gripper is an innovative device designed to grasp objects using the jamming properties of granular materials. However, the granular properties that influence its performance are poorly understood. Moreover, to date, there is no numerical model for the granular gripper. In this paper, we

  8. 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

  9. 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)

  10. 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

  11. 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)

  12. Influence quaternary ammonium salt in the organophilization of an bentonite

    International Nuclear Information System (INIS)

    Oliveira, S.V.; Alves, G.P.; Wanderley, A.S.D.; Araujo, E.M.

    2011-01-01

    Clays are natural materials, earthy, fine-grained particles with diameters generally less than 2μm, and formed by chemically hydrated silicates of aluminum, iron and magnesium. The clays have a range of applications, both in pottery and in other technology areas. This work aimed to study the influence of a quaternary ammonium salt to increase the basal distance of a bentonite clay powder obtained thereby promoting to a new structural profile characteristic with organoclay. The bentonite clay was treated with salt Praepragem WB. The following methods were used: X-ray diffraction (XRD) and X-ray fluorescence (XRF). The results indicated the intercalation of ammonium ions of the salt studied within the layers of silicate and expansion of basal spacing d 001 , ie the clay in the study showed 2θ angle shifts to smaller angles, indicating that the clay was organophilization. (author)

  13. 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 .

  14. 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.)

  15. 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...

  16. 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)

  17. 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.

  18. 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

  19. 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.

  20. Evaluation of Egyptian bentonite and nano-bentonite as drilling mud

    Directory of Open Access Journals (Sweden)

    M.I. Abdou

    2013-06-01

    Full Text Available Nano-particles of bentonite have been prepared by nano-grinding. The nano-bentonite was characterized by X-ray fluorescence analysis (XRF, X-ray powder diffraction (XRD, thermal gravimetric analysis (TGA and Transmission electron microscopy (TEM. The bentonite particles had been ground to the size ranging from 4 to 9 nm. Both natural and nano-bentonite were evaluated as drilling mud. The evaluation involved the study of the rheological properties, filtration and gel strength before and after treatment with viscosities and filter loss agent, and compared with the American Petroleum Institute API bentonite. With decreasing the grain size of bentonite to the nano-scale, the results were not satisfied to the API -standard.

  1. 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

  2. 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.

  3. Pilot-scale road subbase made with granular material formulated with MSWI bottom ash and stabilized APC fly ash: environmental impact assessment.

    Science.gov (United States)

    del Valle-Zermeño, R; Formosa, J; Prieto, M; Nadal, R; Niubó, M; Chimenos, J M

    2014-02-15

    A granular material (GM) to be used as road sub-base was formulated using 80% of weathered bottom ash (WBA) and 20% of mortar. The mortar was prepared separately and consisted in 50% APC and 50% of Portland cement. A pilot-scale study was carried on by constructing three roads in order to environmentally evaluate the performance of GM in a real scenario. By comparing the field results with those of the column experiments, the overestimations observed at laboratory scale can be explained by the potential mechanisms in which water enters into the road body and the pH of the media. An exception was observed in the case of Cu, whose concentration release at the test road was higher. The long-time of exposure at atmospheric conditions might have favoured oxidation of organic matter and therefore the leaching of this element. The results obtained showed that immobilization of all heavy metals and metalloids from APC is achieved by the pozzolanic effect of the cement mortar. This is, to the knowledge of the authors, the only pilot scale study that is considering reutilization of APC as a safe way to disposal. Copyright © 2013 Elsevier B.V. All rights reserved.

  4. Obtaining Carbon Nanomaterials on a Ni-Mo-Bentonite Catalyst

    Science.gov (United States)

    Sataeva, G. E.; Daurenbek, N. M.; Myrzakhmet, M. K.

    2014-05-01

    Investigations into obtaining granulated sorbents based on bentonite clays of the Kyngrack fi eld have been carried out. A pilot-production technology for obtaining carbon composite materials (sorbents and catalysts) has been proposed. The process of formation of catalytic carbon in composites based on Ni-Mo bentonite has been studied on a semicommercial continuous laboratory reactor. It has been established that tubular-fibrous nanosize particles are predominantly formed in the pyrolysis of methane with a Ni-Mo-bentonite catalyst. The efficiency of activation of these sorbents is influenced by the concentration of the clay in them and by their temperature, and also by the consumption of an acid and the time of contact between the solvent and the acid. The structure of the formed nanotubes and nanofibers has been determined with a scanning electron microscope. Optimum parameters and kinetic regularities of the process of obtaining nanotubes and nanofibers at the intermolecular level through their pyrolysis from methane have been obtained.

  5. 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

  6. 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.

  7. 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

  8. Correlation of voidage and stress of granular materials in a packed moving bed accompanied with gas flow; Gasu nagare wo tomonau funtai idoso ni okeru kugekiritsu to funtaiatsu no kankei ni tsuite

    Energy Technology Data Exchange (ETDEWEB)

    Tomoyasu, Yoshitada. [Sanzou Energy Engineering Corp., Okayama (Japan); Yoshino, Fumio.; Iwata, Hiroshi.; Kawazoe, Hiromitsu. [Tottori University, Tottori (Japan). Dept. of Mechanical Engineering

    1999-03-10

    The flow characteristics of granular materials and gas in a vertical packed moving bed, called a [stand pipe], furnished at the bottom of the fluidized bed are investigated theoretically and experimentally. A correlation equation of axial stress {sigma}{sub z} and voidage {epsilon} of granular materials in the stand pipe is proposed through investigations of the continuity equation, the momentum balance equation, Ergun's equation for gas pressure loss and the gas pressure distribution data measured experimentally in the axial direction. Regarding the relation of the axial stress and the voidage, it was recogniged that : 1. The absolute value of d{sigma}{sub z}/d{epsilon} is large at the voidage near the minimum fluidizing condition, and at the voidage in the dense packed condition, and an inflection point of {sigma}{sub z} exists in range between the both conditions ; 2. It seems to be the wall-friction-effect of stand pipe that the absolute value of d{sigma}{sub z}/d{epsilon} is larger at the inlet of stand pipe, and ; 3. The stress is also a function of the particle diameter. The gas flow rate, axial stress distribution of granular materials, gas pressure distribution and voidage distribution in the axial direction of the stand pipe can be calculated from relating equations. (author)

  9. Ion diffusion through highly compacted bentonite

    International Nuclear Information System (INIS)

    Eriksen, T.; Jacobsson, A.; Pusch, R.

    1981-01-01

    Compacted Na- and Ca-bentonites were contacted with aqueous solutions of 134 Cs + , 85 Sr 2+ , 131 I - and 36 Cl - and the diffusivities calculated from tracer concentration-distance profiles in the bentonites 10 days after the onset of diffusion. In the case of 131 I - and 36 Cl - the diffusivities were also determined by measuring the steady state transport through a 5 mm thick bentonite disc. The experimental results indicate that the diffusion through compacted bentonite is governed by complex mechanisms and cannot be accomodated by a simple pore diffusion model. It seems reasonable to assume that non-sorbing ions migrate in the pore water, while cations also move through smectic crystal lattices, preferably through interlamellar spacings according to an ion-exchange-type model. The very low diffusion rate of the investigated anions, as compared with the corresponding rate in bulk water, verifies that the diffusive resistance is very strong for these ions. (Auth.)

  10. 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.

  11. 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.

  12. 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)

  13. An elastoplastic model of bentonite free swelling

    OpenAIRE

    Pintado, Xavier; Alonso Aperte, Juan; Navarro Gamir, Vicente; Asensio, Laura; Yustres Real, Ángel

    2014-01-01

    This article proposes a new plastification mechanism to model bentonite free swelling processes by using an elastoplastic approach. The formulation is based on an interaction function that defines the plastic macrostructural strains induced by microstructural effects. This term is defined as a function of the microstructural void ratio, and it establishes a direct connection between the destructuration of the micro- and macrostructures of the bentonite during the free swelling processes. The ...

  14. 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)

  15. Long-term reactive transport simulations of the interactions of corrosion products and compacted bentonite in a HLW repository

    International Nuclear Information System (INIS)

    Samper, J.; Naves, A.; Montenegro, L.; Mon, A.; Pisani, B.

    2012-01-01

    Document available in extended abstract form only. Carbon steel and compacted bentonite are considered as candidate materials for the overpack and buffer of a nuclear waste in deep geological high level waste (HLW) repositories. Canister corrosion and the chemical interactions of corrosion products with bentonite are key reactions for the long term performance of a repository in granite. Samper et al. (2008a) presented 1-D and 2-D axisymmetric models for the long-term hydrochemical evolution of the porewater composition in the near-field bentonite barrier of a spent-fuel, carbon-steel canister, bentonite and granite repository (ENRESA, 2005). The model accounted for mineral dissolution/precipitation, single-site proton surface complexation and cation exchange of Ca 2+ , Mg 2+ , Na + , K + and Fe 2+ . Canister corrosion was modelled with a constant corrosion rate. The 2-D axisymmetric model accounted for flow in the granite. Lu et al. (2011) extended the model by considering a 1-D axisymmetric model with Fe sorption via surface complexation, three-sites proton surface complexation in the bentonite, constant and kinetically-controlled canister corrosion and magnetite precipitation, the competition effect of Ni 2+ for sorption sites and no water flow through the granite. Here we take a step beyond their models and present an updated version of both reactive transport models. The improved model includes at the same time: 1) Flow through the granite; 2) A three-sites surface complexation model in bentonite; 3) Fe sorption complexation; 4) Kinetically-controlled mineral precipitation; and 5) A dual porosity model for bentonite based on the model developed by Samper et al. (2008b) from laboratory experiments. The model accounts for revised estimates of the initial chemical composition of the bentonite and granite pore waters and assumes corrosion rates based on recent experimental corrosion data collected for carbon steel in contact with compacted bentonite (King, 2008

  16. Sliding through a superlight granular medium.

    Science.gov (United States)

    Pacheco-Vázquez, F; Ruiz-Suárez, J C

    2009-12-01

    We explore the penetration dynamics of an intruder in a granular medium composed of expanded polystyrene spherical particles. Three features distinguish our experiment from others studied so far in granular physics: (a) the impact is horizontal, decoupling the effects of gravity and the drag force; (b) the density of the intruder rho(i) is up to 350 times larger than the density of the granular medium rho(m); and (c) the way the intruder moves through the material, sliding at the bottom of the column with small friction. Under these conditions we find that the final penetration D scales with (rho(i)/rho(m)) and the drag force Fd and D saturate with the height of the granular bed.

  17. Cystic Granular Cell Ameloblastoma

    OpenAIRE

    Thillaikarasi, Rathnavel; Balaji, Jayaram; Gupta, Bhawna; Ilayarja, Vadivel; Vani, Nandimandalam Venkata; Vidula, Balachander; Saravanan, Balasubramaniam; Ponniah, Irulandy

    2010-01-01

    Ameloblastoma is a locally aggressive benign epithelial odontogenic tumor, while unicystic ameloblastoma is a relatively less aggressive variant. Although rare in unicystic or cystic ameloblastoma, granular cell change in ameloblastoma is a recognized phenomenon. The purpose of the present article is to report a case of cystic granular cell ameloblastoma in 34-year old female.

  18. Modeling cation diffusion in compacted water-saturated Na-bentonite at low ionic strength

    International Nuclear Information System (INIS)

    Bourg, Ian C.; Sposito, Garrison; Bourg, Alain C.M.

    2007-01-01

    Sodium bentonites are used as barrier materials for the isolation of landfills and are under consideration for a similar use in the subsurface storage of high-level radioactive waste. The performance of these barriers is determined in large part by molecular diffusion in the bentonite pore space. We tested two current models of cation diffusion in bentonite against experimental data on the relative apparent diffusion coefficients of two representative cations, sodium and strontium. On the 'macropore/nanopore' model, solute molecules are divided into two categories, with unequal pore-scale diffusion coefficients, based on location: in macropores or in interlayer nanopores. On the 'surface diffusion' model, solute molecules are divided into categories based on chemical speciation: dissolved or adsorbed. The macropore/nanopore model agrees with all experimental data at partial montmorillonite dry densities ranging from 0.2 (a dilute bentonite gel) to 1.7 kg dm -3 (a highly compacted bentonite with most of its pore space located in interlayer nanopores), whereas the surface diffusion model fails at partial montmorillonite dry densities greater than about 1.2 kg dm -3

  19. 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).

  20. Modeling cation diffusion in compacted water-saturatedNa-bentonite at low ionic strength

    Energy Technology Data Exchange (ETDEWEB)

    Bourg, Ian C.; Sposito, Garrison; Bourg, Alain C.M.

    2007-08-28

    Sodium bentonites are used as barrier materials for the isolation of landfills and are under consideration for a similar use in the subsurface storage of high-level radioactive waste. The performance of these barriers is determined in large part by molecular diffusion in the bentonite pore space. We tested two current models of cation diffusion in bentonite against experimental data on the relative apparent diffusion coefficients of two representative cations, sodium and strontium. On the 'macropore/nanopore' model, solute molecules are divided into two categories, with unequal pore-scale diffusion coefficients, based on location: in macropores or in interlayer nanopores. On the 'surface diffusion' model, solute molecules are divided into categories based on chemical speciation: dissolved or adsorbed. The macropore/nanopore model agrees with all experimental data at partial montmorillonite dry densities ranging from 0.2 (a dilute bentonite gel) to 1.7 kg dm{sup -3} (a highly compacted bentonite with most of its pore space located in interlayer nanopores), whereas the surface diffusion model fails at partial montmorillonite dry densities greater than about 1.2 kg dm{sup -3}.

  1. 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.

  2. 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

  3. Mechanical properties and mophology natural rubber blend with bentonit and carbon black

    Science.gov (United States)

    Ginting, E. M.; Bukit, N.; Muliani; Frida, E.

    2017-07-01

    Purpose of this study was to determine the mechanical properties and morphology of composite natural rubber and natural bentonite with addition of Na-bentonite filler and carbon black to natural rubber. The method is carried material mixed with filler composition variations (0,10,20,30) phr using open mill for 6 min. Results of the open mill is vulcanized at a temperature of 170°C. Further testing mechanical properties and morphology. Results showed that the addition of Na-bentonite filler and carbon black influence on the mechanical properties of tensile strength, elongation at break, modulus of elasticity, hardness, and strong tear. Morphological results showed cavities in the rubber compound and the occurrence agglomeration.

  4. 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

  5. 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)

  6. 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)

  7. Entropy of jammed granular matter

    Science.gov (United States)

    Briscoe, Christopher

    Granular matter can be considered a non-equilibrium system, such that equilibrium statistics is insufficient to describe the dynamics. A phase transition occurs when granular materials are compressed such that a nonzero stress develops in response to a strain deformation. This transition, referred to as the jamming transition, occurs at a critical volume fraction, φc depending on friction and preparation protocol. Analysis of the jamming transition produces a phase diagram of jammed granular matter for identical spheres, characterized by the critical volume fraction, φc and the average coordination number, Z. The boundaries of the phase diagram are related to well-defined upper and lower limits in the density of disordered packings; random close packing (RCP) and random loose packing (RLP). Frictional systems, such as granular matter, exhibit an inherent path dependency resulting in the loss of energy conservation, an important facet of equilibrium statistics. It has been suggested Edwards that the volume-force (V-F) ensemble, wherein volume replaces energy as the conservative quantity, may provide a sufficient framework to create a statistical ensemble for jammed granular matter. Treating a jammed system via the V-F ensemble introduces an analogue to temperature in equilibrium systems. This analogue, "compactivity", measures how compact a system could be and governs fluctuation in the volume statistics. Randomness in statistical systems is typically characterized by entropy, the equation of state derived from the number of microstates available to the system. In equilibrium statistical mechanics, entropy provides the link between these microstates and the macroscopic thermodynamic properties of the system. Therefore, calculating the entropy within the V-F ensemble can relate the available microscopic volume for each grain to the macroscopic system properties. The entropy is shown to be minimal at RCP and maximal at the minimum RLP limit, via several methods

  8. 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.)

  9. 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)

  10. Crystallisation in a granular material

    Science.gov (United States)

    Francois, N.; Saadatfar, M.; Hanifpour, M.; Cruikshank, R.; Sheppard, A.

    2013-06-01

    The athermal and dissipative nature of packings of grains is still challenging our understanding of their compaction as well as their crystallisation. For instance, some beads poured in a container get jammed in random disordered configurations, which cannot be denser than 64%, the random closed packing (RCP) limit. Remarkably it has been suggested that the RCP bound is saturated with dense patterns of beads aggregated into polytetrahedral structures. Yet when a suitable vibration is applied, a packing of beads might start to order and some regular patterns appear. We present new experiments on the crystallisation of the packing of beads. By extending tapping techniques, we have obtained packings with volume fractions φ ranging from the RCP to the crystal (φ = 0.74). Computing tomography has been used to scan the internal structure of large packings (≈200,000 beads). Voronoi and Delaunay space partitions on the grain centres were performed to characterise the structural rearrangements during the crystallisation. This allows us to describe statistical properties of the local volume fluctuations and the evolution of the densest patterns of beads. In terms of statistical description, a parameter based on the volume fluctuations discloses different regimes during the transition. In terms of geometry, we confirm that polytetrahedral dense clusters are ubiquitous at the RCP. We describe some intrinsic features of these clusters such as rings of tetrahedra and show how they disappear as the crystal grows. This experiment enlightens how an athermal system jammed in a complex frustrated configuration is gradually converted into a periodic crystal.

  11. Collective phenomena in vertically shaken granular matter

    NARCIS (Netherlands)

    Eshuis, Pieter Gerben

    2008-01-01

    Granular matter is the general name for materials consisting of grain-like solids and can be encountered everywhere in our daily life, for instance in the form of sand, sugar, cereals and pills. Numerous industries deal with these kinds of materials, which often cause severe problems during

  12. Discrete Element Modeling of Complex Granular Flows

    Science.gov (United States)

    Movshovitz, N.; Asphaug, E. I.

    2010-12-01

    Granular materials occur almost everywhere in nature, and are actively studied in many fields of research, from food industry to planetary science. One approach to the study of granular media, the continuum approach, attempts to find a constitutive law that determines the material's flow, or strain, under applied stress. The main difficulty with this approach is that granular systems exhibit different behavior under different conditions, behaving at times as an elastic solid (e.g. pile of sand), at times as a viscous fluid (e.g. when poured), or even as a gas (e.g. when shaken). Even if all these physics are accounted for, numerical implementation is made difficult by the wide and often discontinuous ranges in continuum density and sound speed. A different approach is Discrete Element Modeling (DEM). Here the goal is to directly model every grain in the system as a rigid body subject to various body and surface forces. The advantage of this method is that it treats all of the above regimes in the same way, and can easily deal with a system moving back and forth between regimes. But as a granular system typically contains a multitude of individual grains, the direct integration of the system can be very computationally expensive. For this reason most DEM codes are limited to spherical grains of uniform size. However, spherical grains often cannot replicate the behavior of real world granular systems. A simple pile of spherical grains, for example, relies on static friction alone to keep its shape, while in reality a pile of irregular grains can maintain a much steeper angle by interlocking force chains. In the present study we employ a commercial DEM, nVidia's PhysX Engine, originally designed for the game and animation industry, to simulate complex granular flows with irregular, non-spherical grains. This engine runs as a multi threaded process and can be GPU accelerated. We demonstrate the code's ability to physically model granular materials in the three regimes

  13. 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

  14. 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

  15. 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)

  16. 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.)

  17. 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.

  18. 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)

  19. 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

  20. 75 FR 67105 - Granular Polytetrafluoroethylene Resin From Italy and Japan

    Science.gov (United States)

    2010-11-01

    ... COMMISSION Granular Polytetrafluoroethylene Resin From Italy and Japan AGENCY: United States International... granular polytetrafluoroethylene resin from Italy and Japan. SUMMARY: The Commission hereby gives notice... polytetrafluoroethylene resin from Italy and Japan would be likely to lead to continuation or recurrence of material...

  1. 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

  2. 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

  3. 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.)

  4. 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

  5. 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)

  6. COMPARATIVE STUDY ON THORIUM (IV) SORPTION ONTO SODIC BENTONITE AND MAGNETIC BENTONITE

    OpenAIRE

    Didi, Mohamed A.; Miraoui, Abdelkader

    2017-01-01

    In thispaper, the liquid-solid extraction of Thorium (IV) is made by Sodic bentoniteand Magnetic bentonite. Magnetic adsorbent can be quickly separated from amedium by a simple magnetic process, in view of these properties; someparameters were studied to assess the performance of maghemite nanocompositeclay for the removal of Thorium ions. The operating variables studied areinitial La(III) concentration, pH, ionic strength, temperature and contacttime. The time needed for magnetic bentonite t...

  7. Hydraulic properties of dune sand–bentonite mixtures of insulation barriers for hazardous waste facilities

    Directory of Open Access Journals (Sweden)

    M.K. Gueddouda

    2016-08-01

    Full Text Available This paper presents a study on the valorization of local materials such as desert dune sand obtained from Laghouat region in the South Algeria and mine bentonite intended for the realization of liner base layers in the conception of insulation barriers for hazardous waste facilities. In practice, an economical mixture satisfying the hydraulic requirements is generally concerned. First, in order to get an adequate dune sand–bentonite mixture compacted to the optimum Proctor condition, an investigation on saturated hydraulic behavior is carried out in this study for different mixtures. Using oedometer test (indirect measurement, the adequate mixture of 85% dune sand and 15% bentonite satisfies the conditions of saturated hydraulic conductivity (k  3 MPa. This technique is conducted based on the exploitation of the water retention curve in order to establish the relationships between hydraulic conductivity, degree of saturation, and suction. It shows that the hydraulic conductivity increases with the degree of saturation and decreases with the suction. However, the hydraulic conductivity has a constant value for suctions larger than 20 MPa. The selected dune sand–bentonite mixture satisfies the regulation requirements and hence constitutes a good local and economical material for the conception of barrier base liners.

  8. 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.

  9. Granular Leidenfrost effect in vibrated beds with bumpy surfaces.

    Science.gov (United States)

    Lim, E W C

    2010-08-01

    The effects of subjecting a bed of granular materials to horizontal vibrations by a bumpy oscillating surface have been investigated computationally in this study. The behaviour of the granular bed is determined by the vibration conditions applied which include the vibrating frequency and amplitude as well as the bumpiness of the oscillating surface. Under sufficiently vigorous vibration conditions, the granular Leidenfrost effect whereby the entire granular bed is levitated above the vibrating base by a layer of highly energetic particles may be observed. Granular temperature profiles of systems that exhibit the granular Leidenfrost effect indicate an unequal distribution of energy between particles near the vibrating base and those in the bulk. A bumpy oscillating surface was also observed to be more effective at introducing perturbations and transferring energy into a granular bed. The granular Leidenfrost effect can be induced by the application of larger grain sizes of particles constituting the bumpy vibrating base under vibration conditions that are normally insufficient for the onset of the effect. Lastly, a phase diagram which can be utilized for predicting the behaviours of granular beds that are subjected to oscillations by various types of bumpy surfaces has been constructed based on the simulation results obtained.

  10. 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.

  11. 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

  12. 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)

  13. 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

  14. 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

  15. 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

  16. 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.

  17. Collapse of tall granular columns in fluid

    Directory of Open Access Journals (Sweden)

    Kumar Krishna

    2017-01-01

    Full Text Available 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°.

  18. 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°.

  19. Characteristics of undulatory locomotion in granular media

    Science.gov (United States)

    Peng, Zhiwei; Pak, On Shun; Elfring, Gwynn J.

    2016-03-01

    Undulatory locomotion is ubiquitous in nature and observed in different media, from the swimming of flagellated microorganisms in biological fluids, to the slithering of snakes on land, or the locomotion of sandfish lizards in sand. Despite the similarity in the undulating pattern, the swimming characteristics depend on the rheological properties of different media. Analysis of locomotion in granular materials is relatively less developed compared with fluids partially due to a lack of validated force models but recently a resistive force theory in granular media has been proposed and shown useful in studying the locomotion of a sand-swimming lizard. Here we employ the proposed model to investigate the swimming characteristics of a slender filament, of both finite and infinite length, undulating in a granular medium and compare the results with swimming in viscous fluids. In particular, we characterize the effects of drifting and pitching in terms of propulsion speed and efficiency for a finite sinusoidal swimmer. We also find that, similar to Lighthill's results using resistive force theory in viscous fluids, the sawtooth swimmer is the optimal waveform for propulsion speed at a given power consumption in granular media. The results complement our understanding of undulatory locomotion and provide insights into the effective design of locomotive systems in granular media.

  20. 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)

  1. 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)

  2. Removal of metal ions and humic acids through polyetherimide membrane with grafted bentonite clay.

    Science.gov (United States)

    Hebbar, Raghavendra S; Isloor, Arun M; Prabhu, Balakrishna; Inamuddin; Asiri, Abdullah M; Ismail, A F

    2018-03-16

    Functional surfaces and polymers with branched structures have a major impact on physicochemical properties and performance of membrane materials. With the aim of greener approach for enhancement of permeation, fouling resistance and detrimental heavy metal ion rejection capacity of polyetherimide membrane, novel grafting of poly (4-styrenesulfonate) brushes on low cost, natural bentonite was carried out via distillation-precipitation polymerisation method and employed as a performance modifier. It has been demonstrated that, modified bentonite clay exhibited significant improvement in the hydrophilicity, porosity, and water uptake capacity with 3 wt. % of additive dosage. SEM and AFM analysis showed the increase in macrovoides and surface roughness with increased additive concentration. Moreover, the inclusion of modified bentonite displayed an increase in permeation rate and high anti-irreversible fouling properties with reversible fouling ratio of 75.6%. The humic acid rejection study revealed that, PEM-3 membrane having rejection efficiency up to 87.6% and foulants can be easily removed by simple hydraulic cleaning. Further, nanocomposite membranes can be significantly employed for the removal of hazardous heavy metal ions with a rejection rate of 80% and its tentative mechanism was discussed. Conspicuously, bentonite clay-bearing poly (4-styrenesulfonate) brushes are having a synergistic effect on physicochemical properties of nanocomposite membrane to enhance the performance in real field applications.

  3. 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.

  4. 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.

  5. 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

  6. 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)

  7. 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.

  8. 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.

  9. Fluxes of nutrients and trace metals across the sediment-water interface controlled by sediment-capping agents: bentonite and sand.

    Science.gov (United States)

    Han, Junho; Ro, Hee-Myong; Cho, Kyung Hwa; Kim, Kyoung-Woong

    2016-10-01

    The effect of bentonite and sand, as natural capping agents, on the fluxes of nutrients and trace metals across the sediment-water interface was studied through sediment incubation, and the ecotoxicological impact was assessed by using Daphnia magna. Bentonite and sand were layered on the sediment at 15, 75, and 225 mg cm(-2), and the concentration of cations, nutrients, and trace metals was measured. Sediment incubation showed that bentonite reduced the N flux but increased the P flux as a result of dissolution of non-crystalline P from bentonite, while sand slightly decreased the N fluxes but not the P flux. The concentration of Na increased in the overlying water with increasing application rates of bentonite, while that of Ca decreased. However, regardless of the rate of sand application, concentrations of all cation species remained unchanged. The concentration of As and Cr increased with bentonite application rate but decreased with sand. Both capping materials suppressed fluxes of Cd, Cu, Ni, and Zn compared to control, and the extent of suppression was different depending on the trace metal species and capping agents used. During sediment incubation, the survival rate of D. magna significantly decreased in bentonite suspension but began to decrease at the end in sand suspension. Sediment capping of mildly polluted sediments by using bentonite and sand lowered the level of nutrients and trace metals. However, unexpected or undesirable side effects, such as influxes of P and As from bentonite to the overlying water and a possibility of toxic impacts to aquatic ecosystems, were observed, suggesting that capping agents with an adequate assessment of their side effects and toxicity should be predetermined for site-specific sediment management strategies.

  10. 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)

  11. 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

  12. Laboratory investigation of the role of desorption kinetics on americium transport associated with bentonite colloids.

    Science.gov (United States)

    Dittrich, Timothy Mark; Boukhalfa, Hakim; Ware, Stuart Douglas; Reimus, Paul William

    2015-10-01

    Understanding the parameters that control colloid-mediated transport of radionuclides is important for the safe disposal of used nuclear fuel. We report an experimental and reactive transport modeling examination of americium transport in a groundwater-bentonite-fracture fill material system. A series of batch sorption and column transport experiments were conducted to determine the role of desorption kinetics from bentonite colloids in the transport of americium through fracture materials. We used fracture fill material from a shear zone in altered granodiorite collected from the Grimsel Test Site (GTS) in Switzerland and colloidal suspensions generated from FEBEX bentonite, a potential repository backfill material. The colloidal suspension (100 mg L(-1)) was prepared in synthetic groundwater that matched the natural water chemistry at GTS and was spiked with 5.5 × 10(-10) M (241)Am. Batch characterizations indicated that 97% of the americium in the stock suspension was adsorbed to the colloids. Breakthrough experiments conducted by injecting the americium colloidal suspension through three identical columns in series, each with mean residence times of 6 h, show that more than 95% of the bentonite colloids were transported through each of the columns, with modeled colloid filtration rates (k(f)) of 0.01-0.02 h(-1). Am recoveries in each column were 55-60%, and Am desorption rate constants from the colloids, determined from 1-D transport modeling, were 0.96, 0.98, and 0.91 h(-1) in the three columns, respectively. The consistency in Am recoveries and desorption rate constants in each column indicates that the Am was not associated with binding sites of widely-varying strengths on the colloids, as one binding site with fast kinetics represented the system accurately for all three sequential columns. Our data suggest that colloid-mediated transport of Am in a bentonite-fracture fill material system is unlikely to result in transport over long distance scales because

  13. 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

  14. 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

  15. 76 FR 8774 - Granular Polytetrafluoroethylene Resin From Japan

    Science.gov (United States)

    2011-02-15

    ... From the Federal Register Online via the Government Publishing Office INTERNATIONAL TRADE COMMISSION Granular Polytetrafluoroethylene Resin From Japan AGENCY: United States International Trade... polytetrafluoroethylene resin from Japan would be likely to lead to continuation or recurrence of material injury. On...

  16. Bentonite electrical conductivity: a model based on series–parallel transport

    KAUST Repository

    Lima, Ana T.

    2010-01-30

    Bentonite has significant applications nowadays, among them as landfill liners, in concrete industry as a repairing material, and as drilling mud in oil well construction. The application of an electric field to such perimeters is under wide discussion, and subject of many studies. However, to understand the behaviour of such an expansive and plastic material under the influence of an electric field, the perception of its electrical properties is essential. This work serves to compare existing data of such electrical behaviour with new laboratorial results. Electrical conductivity is a pertinent parameter since it indicates how much a material is prone to conduct electricity. In the current study, total conductivity of a compacted porous medium was established to be dependent upon density of the bentonite plug. Therefore, surface conductivity was addressed and a series-parallel transport model used to quantify/predict the total conductivity of the system. © The Author(s) 2010.

  17. Alkali-activated fly ash-based geopolymers with zeolite or bentonite as additives

    Energy Technology Data Exchange (ETDEWEB)

    Mingyu Hu; Xiaomin Zhu; Fumei Long [Nanchang University, Nanchang (China). College of Civil Engineering

    2009-11-15

    Geopolymers were synthesized by using fly ash as the main starting material, zeolite or bentonite as supplementary materials, and NaOH and CaO together as activator. An orthogonal array testing protocol was used to analyze the influence of the mix proportion on the properties of the geopolymers. The results indicate that the concentration of NaOH solution and the CaO content play an important role on the strength of the materials. Especially, with zeolite as additive, the fly ash-based geopolymer shows the highest strength and the best sulfate resistance. Infrared spectroscopy, X-ray, and SEM-EDX demonstrate that supplementary zeolite may involve the process of geopolymerization to form a stable zeolitic structure and improve the properties of the geopolymer. Bentonite simply acts as a filler to make the geopolymer more compact, but shows no improvement on the compositions and the microstructures of the geopolymer.

  18. Granular Cell Tumor

    African Journals Online (AJOL)

    Necrosis within the tumor was absent, no mitosis was. Granular cell tumors are seldom diagnosed identified in the section and the edges of the accurately clinically. The lesion in this case was sample were tumor free (Figure 2). mistaken for a sebaceous cyst and following ulceration resembled carcinoma of the vulvar.

  19. On the submerging of a spherical intruder into granular beds

    Directory of Open Access Journals (Sweden)

    Wu Chuan-Yu

    2017-01-01

    Full Text Available Granular materials are complex systems and their mechanical behaviours are determined by the material properties of individual particles, the interaction between particles and the surrounding media, which are still incompletely understood. Using an advanced discrete element method (DEM, we simulate the submerging process of a spherical projectile (an intruder into granular materials of various properties with a zero penetration velocity (i.e. the intruder is touching the top surface of the granular bed and released from stationary and examine its settling behaviour. By systematically changing the density and size of the intruder and the particle density (i.e. the density of the particles in the granular bed, we find that the intruder can sink deep into the granular bed even with a zero penetration velocity. Furthermore, we confirm that under certain conditions the granular bed can behave like a Newtonian liquid and the submerging intruder can reach a constant velocity, i.e. the terminal velocity, identical to the settling of a sphere in a liquid, as observed experimentally. A mathematical model is also developed to predict the maximum penetration depth of the intruder. The model predictions are compared with experimental data reported in the literature,good agreement was obtained, demonstrating the model can accurately predict the submerging behaviour of the intruder in the granular media.

  20. On the submerging of a spherical intruder into granular beds

    Science.gov (United States)

    Wu, Chuan-Yu; Zhang, Ling; Chen, Lan

    2017-06-01

    Granular materials are complex systems and their mechanical behaviours are determined by the material properties of individual particles, the interaction between particles and the surrounding media, which are still incompletely understood. Using an advanced discrete element method (DEM), we simulate the submerging process of a spherical projectile (an intruder) into granular materials of various properties with a zero penetration velocity (i.e. the intruder is touching the top surface of the granular bed and released from stationary) and examine its settling behaviour. By systematically changing the density and size of the intruder and the particle density (i.e. the density of the particles in the granular bed), we find that the intruder can sink deep into the granular bed even with a zero penetration velocity. Furthermore, we confirm that under certain conditions the granular bed can behave like a Newtonian liquid and the submerging intruder can reach a constant velocity, i.e. the terminal velocity, identical to the settling of a sphere in a liquid, as observed experimentally. A mathematical model is also developed to predict the maximum penetration depth of the intruder. The model predictions are compared with experimental data reported in the literature,good agreement was obtained, demonstrating the model can accurately predict the submerging behaviour of the intruder in the granular media.

  1. Interaction between tylosin and bentonite clay from a pharmacokinetic perspective.

    Science.gov (United States)

    Devreese, Mathias; Osselaere, Ann; Goossens, Joline; Vandenbroucke, Virginie; De Baere, Siegrid; De Backer, Patrick; Croubels, Siska

    2012-12-01

    The interaction between bentonite and tylosin was investigated in broiler chickens, based on pharmacokinetic characteristics obtained in vivo. Simultaneous oral administration of bentonite and tylosin significantly lowered plasma levels of tylosin and reduced the area under the plasma concentration-time curve (AUC(0-inf)), maximal plasma concentration (C(max)), time to maximal plasma concentration (T(max)) and relative oral bioavailability. The results prove unambiguously the binding of tylosin by bentonite. Simultaneous administration of tylosin (in the drinking water or feed) and bentonite (mixed in the feed as a mycotoxin binder) should therefore be avoided. Copyright © 2012 Elsevier Ltd. All rights reserved.

  2. Synthesis of PDLLA/PLLA-bentonite nanocomposite through sonication

    International Nuclear Information System (INIS)

    Sitompul, Johnner; Setyawan, Daru; Kim, Daniel Young Joon; Lee, Hyung Woo

    2016-01-01

    This paper concerns the synthesis of poly(D,L-lactic acid)/poly(L-lactic acid) bentonite nanocomposites. Poly (D,L-lactic acid) (PDLLA) was synthesized using lactic acid through the ZnO-catalyzed direct polycondensation method at vacuum pressure and poly(L-lactic acid) (PLLA) was synthesized with L-lactide by ring-opening polymerization method. The PDLLA/PLLA-bentonite nanocomposite films were synthesized using the solvent casting method. The nanoclay, bentonite, was prepared using the solution-intercalation method by dissolving the nanoparticles into chloroform before sonication. In this study, PDLLA/PLLA-bentonite nanocomposite films were produced using variable amounts of nanoclay and sonication times during the mixing of PDLLA/PLLA and bentonite. The properties of the PDLLA/PLLA nanocomposites were then characterized using the X-ray Diffraction (XRD), Universal Testing Machine (UTM), Water Vapor Permeability (WVP) tests, and the enzymatic biodegradability test. The XRD test was used to measure the intercalation of nanoclay layers in the PDLLA/PLLA matrix and the PDLLA/PLLA-bentonite intercalated nanocomposite films. It was found through these various tests that adding bentonite to the PDLLA/PLLA increases tensile strength to 56.76 MP. Furthermore, the biodegradability increases as well as the barrier properties of the polymers The different sonication time used during the mixing of the polymer solution with bentonite also affected the properties of the PDLLA/PLLA-bentonite nanocomposite films.

  3. Study on Adsorption Mechanism of Acid-Modified Bentonite

    Science.gov (United States)

    Peng, L. G.; Zhu, J. H.; Han, J.; Wang, X. X.; Zhao, M.; Cheng, H. Q.; Zhang, X.

    2017-12-01

    The acid-modified bentonite was prepared by sulfuric acid acidification, we compared it in chemical composition, layer structure and adsorption performance before and after the adsorption of Cu2+ by joint analysis of FT-IR, XRD, and ICP. The results indicated that: XRD showed that Cu2+ went into the bentonite layer, the analysis of ICP showed: Cu2+ exchange reaction didn’t take place, only coordination reaction occurred, i.e. acid-modified bentonite adsorbs cooper irons mainly in a way of cooperation reaction; the adsorption of acid-modified bentonite conforms to the Langmuir monolayer model and the pseudo-second-order kinetic model.

  4. Synthesis of PDLLA/PLLA-bentonite nanocomposite through sonication

    Energy Technology Data Exchange (ETDEWEB)

    Sitompul, Johnner, E-mail: sitompul@che.itb.ac.id; Setyawan, Daru, E-mail: daru.setyawan@gmail.com; Kim, Daniel Young Joon, E-mail: daniel.kim12321@gmail.com [Department of Chemical Engineering, Faculty of Industrial Technology, Institute of Technology Bandung Jl. Ganesha 10, Bandung, West Java, 40132 (Indonesia); Lee, Hyung Woo, E-mail: leehw@che.itb.ac.id [Department of Chemical Engineering, Faculty of Industrial Technology, Institute of Technology Bandung Jl. Ganesha 10, Bandung, West Java, 40132 (Indonesia); Research and Business Foundation, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi, 440-746 (Korea, Republic of)

    2016-04-19

    This paper concerns the synthesis of poly(D,L-lactic acid)/poly(L-lactic acid) bentonite nanocomposites. Poly (D,L-lactic acid) (PDLLA) was synthesized using lactic acid through the ZnO-catalyzed direct polycondensation method at vacuum pressure and poly(L-lactic acid) (PLLA) was synthesized with L-lactide by ring-opening polymerization method. The PDLLA/PLLA-bentonite nanocomposite films were synthesized using the solvent casting method. The nanoclay, bentonite, was prepared using the solution-intercalation method by dissolving the nanoparticles into chloroform before sonication. In this study, PDLLA/PLLA-bentonite nanocomposite films were produced using variable amounts of nanoclay and sonication times during the mixing of PDLLA/PLLA and bentonite. The properties of the PDLLA/PLLA nanocomposites were then characterized using the X-ray Diffraction (XRD), Universal Testing Machine (UTM), Water Vapor Permeability (WVP) tests, and the enzymatic biodegradability test. The XRD test was used to measure the intercalation of nanoclay layers in the PDLLA/PLLA matrix and the PDLLA/PLLA-bentonite intercalated nanocomposite films. It was found through these various tests that adding bentonite to the PDLLA/PLLA increases tensile strength to 56.76 MP. Furthermore, the biodegradability increases as well as the barrier properties of the polymers The different sonication time used during the mixing of the polymer solution with bentonite also affected the properties of the PDLLA/PLLA-bentonite nanocomposite films.

  5. Geomechanical characterisation of unsaturated Kunigel V1 bentonite: swelling and shear strength

    International Nuclear Information System (INIS)

    Yamamoto, S.; Shimura, T.; Asano, H.; Namiki, K.; Romero, E.; Kato, S.

    2012-01-01

    Document available in extended abstract form only. The development and validation of hydro-geomechanical models for bentonite buffer are one of the important subjects to appropriately evaluate long term behaviour of EBS in radioactive waste disposal. The Barcelona Basic Model (BBM), which is one extension of the modified Cam- Clay model for unsaturated and expansive soil, has been developed and widely applied to several hydro-geomechanical problems by using the coupled THM code, Code-Bright. Some advantages of the model are that hydro-geomechanical characteristics of buffer materials under saturated and partially saturated conditions are taken into account as well as the swelling characteristics due to wetting. Applicability of the BBM to consolidation and swelling behaviour of unsaturated bentonite has already been confirmed. In this study swelling characteristics of unsaturated bentonite are further discussed based on results from controlled-suction odometer tests, and in addition shear strength depending on matric suction is discussed based on controlled-suction triaxial compression tests. Swelling tests of compacted bentonite (Kunigel V1, initial dry density: 1.0 Mg/m 3 ) under constant confined vertical net stresses (20 and 100 kPa) were performed by using controlled-suction odometer cells. Matrice suction was stepwise reduced from 500 kPa to 0 kPa by 100 kPa. It is found that swelling is more dominant in latter step of the suction change (i.e., closer steps to saturation), especially the step from 100 kPa to 0 kPa. Swelling due to wetting, i.e. decrease in matric suction is defined in the BBM. Controlled-suction triaxial compression tests of compacted bentonite (Kunigel V1, initial dry density: 1.36 Mg/m 3 ) under both constant matric suctions (0, 300, and 500 kPa) and constant confined lateral net stresses were performed to study dependency of shear strength on matric suction. It is found that the apparent cohesion linearly increases with increase in matric

  6. Swelling pressure of highly compacted bentonite

    International Nuclear Information System (INIS)

    Pusch, R.

    1980-08-01

    Highly compacted, dense Na bentonite is used to isolate metal canisters with highly radioactivity waste products from the surrounding rock. The main object was to investigate the relationship between the swelling pressure and bulk density of bentonite with special reference to the influence of ion exchange and temperature. A new type of oedometer for swelling pressure tests was developed. It was found that there seemed to be unique relationship between the bulk density and the sweeling pressure, and that a temperature increase to 70deg C reduced the pressure to approximately 50% of the value at 20degC. It was observed that the pore water chemistry was hardle a determinant of the swelling pressure in the bulk density above 2 ton per m 3 . (G.B.)

  7. A coupled THMC model of a heating and hydration laboratory experiment in unsaturated compacted FEBEX bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, L.; Samper, J.; Montenegro, L.; Fernandez, A.M.

    2010-05-01

    Unsaturated compacted bentonite is foreseen by several countries as a backfill and sealing material in high-level radioactive waste repositories. The strong interplays between thermal (T), hydrodynamic (H), mechanical (M) and chemical (C) processes during the hydration stage of a repository call for fully coupled THMC models. Validation of such THMC models is prevented by the lack of comprehensive THMC experiments and the difficulties of experimental methods to measure accurately the chemical composition of bentonite porewater. We present here a non-isothermal multiphase flow and multicomponent reactive solute transport model for a deformable medium of a heating and hydration experiment performed on a sample of compacted FEBEX bentonite. Besides standard solute transport and geochemical processes, the model accounts for solute cross diffusion and thermal and chemical osmosis. Bentonite swelling is solved with a state-surface approach. The THM model is calibrated with transient temperature, water content and porosity data measured at the end of the experiment. The reactive transport model is calibrated with porewater chemical data derived from aqueous extract data. Model results confirm that thermal osmosis is relevant for the hydration of FEBEX bentonite while chemical osmosis can be safely neglected. Dilution and evaporation are the main processes controlling the concentration of conservative species. Dissolved cations are mostly affected by calcite dissolution-precipitation and cation exchange reactions. Dissolved sulphate is controlled by gypsum/anhydrite dissolution-precipitation. pH is mostly buffered by protonation/deprotonation via surface complexation. Computed concentrations agree well with inferred aqueous extract data at all sections except near the hydration boundary where cation data are affected by a sampling artifact. The fit of Cl{sup -} data is excellent except for the data near the heater. The largest deviations of the model from inferred aqueous

  8. Bentonites in powder detergents: softness and perfum

    OpenAIRE

    Bernal, Cristóbal; Carrión Fité, Francisco Javier

    2011-01-01

    The sodium bentonite is a mineral composed by hydrated aluminium silicates with a great capacity for absorbing several types of substrates. In cotton articles, softeners are added after the washing process. Softeners are organic products which are absorbed within the last rinse. These types of softeners can present some disadvantages as the possible lack of biodegradability, solidity and higher hydrophobicity which might reduce the sensation of comfort in the clothes as water absorption is di...

  9. Borehole sealing with highly compactd Na bentonite

    International Nuclear Information System (INIS)

    Pusch, R.

    1981-12-01

    This report describes the use of highly compacted Na bentonite for borehole plugging. Bentonites have an extremely low permeability and a low diffusivity, and a swelling ability which produces a nonleaching boundary between clay and rock if the initial bulk density of the bentonite is sufficiently high. The suggested technique, which is applicable to long vertical, and inclined, as well as horizontal boreholes, is based on the use of perforated copper pipes to insert elements of compacted bentonite. Such pipe segments are connected at the rock surface and successively inserted in the hole. When the hole is equipped, the clay takes up water spontaneously and swells through the perforation, and ultimately forms an almost completely homogenous clay core. It embeds the pipe which is left in the hole. Several tests were conducted in the laboratory and one field test was run in Stripa. They all showed that a gel soon fills the slot between the pipe and the confinement which had the form of metal pipes in the laboratory investigations. Subsequently, more clay migrates through the perforation and produces a stiff clay filling in the slot. The redistribution of minerals, leading ultimately to a high degree of homogeneity, can be described as a diffusion process. The rate of redistribution depends on the joint geometry and water flow pattern in the rock. In the rock with an average joint frequence of one per meter or higher, very good homogeneity and sealing ability of the clay are expected within a few months after the application of the plug. (author)

  10. Traffic and Granular Flow’05

    CERN Document Server

    Pöschel, Thorsten; Kühne, Reinhart; Schreckenberg, Michael; Wolf, Dietrich

    2007-01-01

    The conference series Tra?c and Granular Flow has been established in 1995 and has since then been held biannually. At that time, the investigation of granular materials and tra?c was still somewhat exotic and was just starting to become popular among physicists. Originally the idea behind this conference series was to facilitate the c- vergence of the two ?elds, inspired by the similarities of certain phenomena and the use of similar theoretical methods. However, in recent years it has become clear that probably the di?erences between the two systems are much more interesting than the similarities. Nevertheless, the importance of various interrelations among these ?elds is still growing. The workshop continues to o?er an opportunity to stimulate this interdisciplinary research. Over the years the spectrum of topics has become much broader and has included also problems related to topics ranging from social dynamics to - ology. The conference manages to bring together people with rather di?erent background, r...

  11. Controlling wave propagation through nonlinear engineered granular systems

    Science.gov (United States)

    Leonard, Andrea

    We study the fundamental dynamic behavior of a special class of ordered granular systems in order to design new, structured materials with unique physical properties. The dynamic properties of granular systems are dictated by the nonlinear, Hertzian, potential in compression and zero tensile strength resulting from the discrete material structure. Engineering the underlying particle arrangement of granular systems allows for unique dynamic properties, not observed in natural, disordered granular media. While extensive studies on 1D granular crystals have suggested their usefulness for a variety of engineering applications, considerably less attention has been given to higher-dimensional systems. The extension of these studies in higher dimensions could enable the discovery of richer physical phenomena not possible in 1D, such as spatial redirection and anisotropic energy trapping. We present experiments, numerical simulation (based on a discrete particle model), and in some cases theoretical predictions for several engineered granular systems, studying the effects of particle arrangement on the highly nonlinear transient wave propagation to develop means for controlling the wave propagation pathways. The first component of this thesis studies the stress wave propagation resulting from a localized impulsive loading for three different 2D particle lattice structures: square, centered square, and hexagonal granular crystals. By varying the lattice structure, we observe a wide range of properties for the propagating stress waves: quasi-1D solitary wave propagation, fully 2D wave propagation with tunable wave front shapes, and 2D pulsed wave propagation. Additionally the effects of weak disorder, inevitably present in real granular systems, are investigated. The second half of this thesis studies the solitary wave propagation through 2D and 3D ordered networks of granular chains, reducing the effective density compared to granular crystals by selectively placing wave

  12. Changes on the mineralogical and physico-chemical properties of a compacted bentonite in contact with hyperalkaline pore fluids

    International Nuclear Information System (INIS)

    Fernandez, A.M.; Melon, A.; Sanchez, D.M.

    2010-01-01

    Document available in extended abstract form only. In high-level radioactive waste disposal (HLW) concepts, compacted bentonites are being considered in many countries as a sealing material because of their low permeability, high swelling capacity and high plasticity. In the case of the geological disposal of nuclear wastes in argillaceous host formations, concrete will be also used as support of tunnels and galleries and as waste containment material. Therefore, the bentonite barrier will become saturated with the water resulting from the host-rock/concrete interaction. An understanding of the rate and nature of the bentonite alteration, as well as the evolution of the bentonite pore water in the long-term is important for performance assessment. In this work the behaviour of the bentonite has been simulated in a laboratory test. A concrete-bentonite interaction experiment has been performed at a high solid to liquid ratio with FEBEX bentonite. The aim of the experiment was to analyse the buffering capacity of the bentonite and the clay mineral stability in a high-pH environment over a long contact period. The rate of pH buffering capacity of the bentonite is related to its surface hydroxyl sites (≡SOH) located along the edges of the clay platelets (fast reaction), and the montmorillonite crystal lattice itself (governed by reaction kinetics). Two infiltration tests with hyper-alkaline water were performed with FEBEX bentonite compacted at a dry density of 1.65 g/cm 3 with a hygroscopic water content (w.c.) of 13.4% in small-scale hermetic cells (50- mm diameter and 25-mm high). The experiments were running for 1.65 years under anoxic conditions inside an anoxic glove (< 1 ppm O 2 ) box and at temperature of 30-35 deg. C. The type of alkaline solution was a Na-K-OH water in equilibrium with portlandite, Ca(OH) 2 , at pH 13.5. This water is representative of an average pore water of a mortar made with CEM-I-SR type Portland cement (sulphate-resistant) at a 0

  13. Preparation and characterization of bentonite clay for formation of nanocomposites

    International Nuclear Information System (INIS)

    Santos, J.J.M.; Silva, B.L.; Araujo, I.J.C.; Medeiros, A.M.; Melo, J.D.D.; Paskocimas, C.A.

    2011-01-01

    This study we used the linear medium density polyethylene (PELMD) as polymer matrix and introduced, as reinforcement to increase the mechanical and thermal properties, the green bentonite deposit of Boa Vista/PB, rich montmorillonite (MMT), previously characterized by XRD, that passed by three stages of purification. The first stage was to clean by washing and filtering for removal of coarse material (sand and organic matter), followed by an acid attack. In the second, we used the quaternary ammonium surfactant, in order to increase the distance between the layers of MMT, and the third was removed from the wastewater, using absolute ethanol, finishing the purification of process. Then, the clay was introduced into the polymer matrix by polymerization in solution by intercalation and characterized by XRD. The results showed a partial exfoliation, satisfying the increasing properties. (author)

  14. Sorption behaviour of caesium on a bentonite sample

    International Nuclear Information System (INIS)

    Hurel, C.; Marmier, N.; Fromage, F.; Seby, F.; Bourg, A.C.M.; Giffaut, E.

    2002-01-01

    Sorption of elements like Cs on clay is one of the principal processes delaying their release from deep repositories of nuclear wastes into the environment. The sorption processes taking place between non-purified natural clay material (bentonite) and synthetic groundwater (containing Ca, Mg, Na, K and carbonates) were therefore studied experimentally and modelled for Cs to determine whether thermodynamic computer codes capable of predicting the behaviour of this element in natural systems might be developed. The model used, based on the properties of a pure montmorillonite phase, incorporates the surface reactions for natural major ions and sorbing cations but does not have any adjustable parameters. The weight of each parameters used in the model is assessed. Surface reactions are classified as either major or minor, and a simplified model of Cs sorption that considers only the major processes is proposed. This simplified model might correspond to the less sophisticated thermodynamic model included in coupled geochemistry-transport models. (orig.)

  15. Decantation time of evaluation on bentonite clays fractionation; Avaliacao do tempo de decantacao no fracionamento de argilas bentonitas

    Energy Technology Data Exchange (ETDEWEB)

    Gomes, J.; Menezes, R.R.; Neves, G.A.; Lira, H.L; Santana, L.N.L., E-mail: lisiane@dema.ufcg.edu.b [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Dept. de Engenharia de Materiais

    2009-07-01

    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)

  16. Study on chemical buffering property of GMZ sodium bentonite in air

    International Nuclear Information System (INIS)

    Wen Zhijian; Liu Yuemiao; Zong Zihua; Zhou Jia

    2008-01-01

    The high level radioactive wastes are characterized by very high initial radioactivity, the longer-lived actinides, many of actinides alpha-emitters. At present, the deep geological disposal is regarded as the most reasonable and effective way to safely disposal high-level radioactive wastes in the world. The conceptual model of HLW geological disposal in China is based on a multi-barrier system that combines an isolating geological environment with an engineered barrier system. The buffer is one of the engineered barrier materials and GMZ Na-bentonite is selected as the base material. The most important role related to buffer is chemical buffering, which means buffering of changes in water chemistry. This paper presents the experiments of GMZ-1 Na-bentonite reacted with distilled water in the air. The results and discussion of bench tests are reported. (authors)

  17. Modelling interaction of deep groundwaters with bentonite and radionuclide speciation

    International Nuclear Information System (INIS)

    Wanner, H.

    1986-04-01

    In the safety analysis recently reported for a potential Swiss high-level waste repository, radionuclide speciation and solubility limits are calculated for expected granitic groundwater conditions. With the objective of deriving a more realistic description of radionuclide release from the near-field, an investigation has been initiated to quantitatively specify the chemistry of the near-field. In the Swiss case, the main components of the near-field are the glass waste-matrix, a thick steel canister horizontally emplaced in a drift, and a backfill of highly compacted sodium bentonite. This report describes a thermodynamic model which is used to estimate the chemical composition of the pore water in compacted sodium bentonite. Solubility limits and speciation of important actinides and the fission product technetium in the bentonite pore water are then calculated. The model is based on available experimental data on the interaction of sodium bentonite and groundwater and represents means of extrapolation from laboratory data to repository conditions. The modelled composition of the pore water of compacted sodium bentonite, as well as the various compositions resulting from the long-term extrapolation, are used to estimate radionuclide solubilities in the near-field of a deep repository. From the chemical point of view, calcium bentonite seems to be more stable than sodium bentonite in the presence of Swiss Reference Groundwater. Since the effect of calcium bentonite on the groundwater chemical composition will be considerably less marked than that of sodium bentonite, especially with respect to key parameters for the nuclide speciation like carbonate concentration and pH, the use of calcium bentonite instead of sodium bentonite will improve the reliability in the prediction of source terms for radionuclide transport in the geosphere. (author)

  18. Long-term alteration of bentonite in the presence of metallic iron

    International Nuclear Information System (INIS)

    Kumpulainen, Sirpa; Kiviranta, Leena; Carlsson, Torbjoern; Muurinen, Arto; Svensson, Daniel; Sasamoto, Hiroshi; Yui, Mikatzu; Wersin, Paul; Rosch, Dominic

    2010-05-01

    According to the KBS-3H concept, each copper canister containing spent nuclear fuel will be surrounded by a bentonite buffer and a perforated steel cylinder. Since steel is unstable in wet bentonite, it will corrode and the corrosion products will interact with the surrounding bentonite in ways that are not fully understood. Such interaction may seriously impair the bentonite's functioning as a buffer material, e.g. by lowering its CEC or decreasing its swelling capacity. This report presents results from two iron-bentonite experiments carried out under quite different conditions at VTT (Finland) and JAEA (Japan). Both studies focused on long-term iron-bentonite interactions under anaerobic conditions. The study at VTT comprised eight years long experiments focused on diffusive based interactions between solid cast-iron and compacted MX-80 bentonite (dry density 1.5-1.6 g/cm 3 ) in contact with an aqueous 0.5 M NaCl solution. The study at JAEA comprised ten years long batch experiments, each involving a mixture of metallic iron powder (25 g), an industrially refined Na bentonite, Kunipia F, which contains more than 99% montmorillonite (25 g), and an aqueous solution (250 mL). Samples were sent to B+Tech in airtight steel vessels filled with N 2 and subsequently analyzed at various laboratories in Finland and Sweden. The JAEA samples differed with regard to the initial solution chemistry, which was either distilled water, 0.3 M NaCl, 0.6 M NaCl, 0.1 M NaHCO 3 , or 0.05 M Na 2 SO 4 . The analyses of the MX-80 bentonite samples were carried out on samples containing a cast iron cylinder and also on corresponding background samples with no cast iron. In addition, the external solution and gas phase in contact with the bentonite were analyzed. Briefly, the gas contained H 2 , most possibly caused by corrosion of the cast iron, and CO 2 , mainly as a result of carbonate dissolution. The eight years old external solution exhibited, inter alia, reducing conditions, a pH of

  19. Long-term alteration of bentonite in the presence of metallic iron

    Energy Technology Data Exchange (ETDEWEB)

    Kumpulainen, Sirpa; Kiviranta, Leena (BandTech Oy (Finland)); Carlsson, Torbjoern; Muurinen, Arto (VTT (Finland)); Svensson, Daniel (Svensk Kaernbraenslehantering AB (Sweden)); Sasamoto, Hiroshi; Yui, Mikatzu (JAEA (Japan)); Wersin, Paul; Rosch, Dominic (Gruner Ltd (Switzerland))

    2010-05-15

    According to the KBS-3H concept, each copper canister containing spent nuclear fuel will be surrounded by a bentonite buffer and a perforated steel cylinder. Since steel is unstable in wet bentonite, it will corrode and the corrosion products will interact with the surrounding bentonite in ways that are not fully understood. Such interaction may seriously impair the bentonite's functioning as a buffer material, e.g. by lowering its CEC or decreasing its swelling capacity. This report presents results from two iron-bentonite experiments carried out under quite different conditions at VTT (Finland) and JAEA (Japan). Both studies focused on long-term iron-bentonite interactions under anaerobic conditions. The study at VTT comprised eight years long experiments focused on diffusive based interactions between solid cast-iron and compacted MX-80 bentonite (dry density 1.5-1.6 g/cm3) in contact with an aqueous 0.5 M NaCl solution. The study at JAEA comprised ten years long batch experiments, each involving a mixture of metallic iron powder (25 g), an industrially refined Na bentonite, Kunipia F, which contains more than 99% montmorillonite (25 g), and an aqueous solution (250 mL). Samples were sent to B+Tech in airtight steel vessels filled with N{sub 2} and subsequently analyzed at various laboratories in Finland and Sweden. The JAEA samples differed with regard to the initial solution chemistry, which was either distilled water, 0.3 M NaCl, 0.6 M NaCl, 0.1 M NaHCO{sub 3}, or 0.05 M Na{sub 2}SO{sub 4}. The analyses of the MX-80 bentonite samples were carried out on samples containing a cast iron cylinder and also on corresponding background samples with no cast iron. In addition, the external solution and gas phase in contact with the bentonite were analyzed. Briefly, the gas contained H{sub 2}, most possibly caused by corrosion of the cast iron, and CO{sub 2}, mainly as a result of carbonate dissolution. The eight years old external solution exhibited, inter alia

  20. An unsaturated hydraulic conductivity model for compacted GMZ01 bentonite with consideration of temperature

    OpenAIRE

    YE, Wei-Min; WAN, Min; CHEN, Bao; CHEN, Yong-Gui; CUI, Yu-Jun; WANG, Ju

    2014-01-01

    As one of the most important properties of compacted bentonite used as buffer/backfill materials, hydraulic conductivity is influenced by various factors including temperature, microstructure and suction (or degree of saturation), etc. Based on the readily available results of both temperature-controlled water-retention tests and unsaturated infiltration tests under confined (constant volume) conditions, influences of temperature and microstructure variations on unsaturated hydraulic conducti...

  1. Swelling compositions based polycarboxylic acids and bentonite clays in solutions of salts of metals

    Directory of Open Access Journals (Sweden)

    A. Sarshesheva

    2012-12-01

    Full Text Available This work is devoted to the synthesis of chemical cross-linked composite materials made of natural inorganic polymer bentonite clay of Manrak deposit, and polyacrylic and polymethacrylic acids. The swelling ability of the composition in solutions of salts of heavy metals (Ni2+ and Pb2+, influence of solution of concentration, pH and temperature on the swelling ability is investigated.

  2. Patterning of a cohesionless granular layer under pure shear

    Science.gov (United States)

    Alarcón, Héctor; Géminard, Jean-Christophe; Melo, Francisco

    2018-01-01

    The response of a thin layer of granular material to an external pure shear imposed at its base is investigated. The experiments show that, even for noncohesive materials, the resulting deformation of the material is inhomogeneous. Indeed, a novel smooth pattern, consisting of a periodic modulation of the shear deformation of the free surface, is revealed by an image-correlation technique. These observations are in contrast with the previous observation of the fracture pattern in cohesive granular materials subjected to stretching. For cohesive materials, the instability is due to the weakening of the material which results from the rupture of capillary bridges that bond the grains to one another. For noncohesive materials, the rupture of the capillary bridges cannot be invoked anymore. We show that the instability results from the decrease of friction on shearing. PACS: 89.75.Kd: Pattern formation in complex systems; 83.60.Uv: Rheology: fracture; 45.70.Qj: Pattern formation in granular matter

  3. Dynamics of electrostatically driven granular media: Effects of humidity

    International Nuclear Information System (INIS)

    Howell, D. W.; Aronson, Igor S.; Crabtree, G. W.

    2001-01-01

    We performed experimental studies of the effect of humidity on the dynamics of electrostatically driven granular materials. Both conducting and dielectric particles undergo a phase transition from an immobile state (granular solid) to a fluidized state (granular gas) with increasing applied field. Spontaneous precipitation of solid clusters from the gas phase occurs as the external driving is decreased. The clustering dynamics in conducting particles is primarily controlled by screening of the electric field but is aided by cohesion due to humidity. It is shown that humidity effects dominate the clustering process with dielectric particles

  4. The self-propulsion of a helix in granular matter

    Science.gov (United States)

    Valdes, Rogelio; Angeles, Veronica; de La Calleja, Elsa; Zenit, Roberto

    2017-11-01

    The effect of the shape of helicoidal on the displacement of magnetic robots in granular media is studied experimentally. We quantify the influences of three main parameters of the shape of the helicoidal swimmers: body diameter, step, and the angle. We compare the experimental measurements with an empirically modified resistive force theory prediction that accounts for the static friction coefficient of the particles of the granular material, leading to good agreement. Comparisons are also made with the granular resistive force theory proposed by Goldman and collaborators. We found an optimal helix angle to produce movement and determined a relationship between the swimmer size and speed.

  5. Effect of wet-dry cycles on polymer treated bentonite in seawater : swelling ability, hydraulic conductivity and crack analysis

    NARCIS (Netherlands)

    De Camillis, Michela; Di Emidio, Gemmina; Bezuijen, Adam; Verastegui Flores, Daniel; Van Stappen, Jeroen; Cnudde, Veerle

    2017-01-01

    Waste disposal facilities are often isolated by clay liners in order to prevent pollutant migration into the ground. Bentonite is used as barrier material thanks to the low conductivity to water. However, the hydraulic performance may be impaired by contact with aggressive liquids due to cation

  6. A comparative study of the flow enhancing properties of bentonite ...

    African Journals Online (AJOL)

    A comparative study of granule flow enhancing property of bentonite, magnesium stearate, talc and microcrystalline cellulose (MCC) was undertaken. Bentonite was processed into fine powder. A 10 %w/w of starch granules was prepared and separated into different sizes (˂180, 180-500, 500-710 and 710-850 μm).

  7. Mechanical properties of crushed salt/bentonite blocks

    International Nuclear Information System (INIS)

    Gerstle, W.H.; Jones, A.K.

    1986-08-01

    A preliminary mechanical testing program has been conducted on crushed salt/bentonite blocks. These blocks are pototypes of blocks that may eventually be used to build engineered seals in drifts at the WIPP site. Three types of blocks were tested: pure crushed salt, crushed salt with bentonite binder, and pure bentonite. Simple uniaxial compression tests were performed. Axial displacement and lateral displacements were measured as a function of applied axial load. The ultimate strength, initial elastic moduli, and mode of failure were determined from these tests. The ultimate uniaxial strength of the pure bentonite blocks were found to be about 6.8 MPa. The ultimate uniaxial strength of pure salt blocks were found to be about 3.2 MPa. The blocks composed of both salt and bentonite had a strength somewhere between these two values. Surprisingly, the bentonite blocks, while stronger than the pure salt blocks, were less stiff. The mode of failure in all cases was through longitudinal splitting cracking. Also, ultrasonic velocities in the blocks were measured. The results of these tests indicate a high degree of anisotropy in the bentonite and salt/bentonite blocks, while the pure salt blocks appear to be isotropic

  8. Filtration behavior of organic substance through a compacted bentonite

    International Nuclear Information System (INIS)

    Kanaji, Mariko; Kuno, Yoshio; Yui, Mikazu

    1999-07-01

    Filtration behavior of organic substance through a compacted bentonite was investigated. Na-type bentonite containing 30wt% of quartz sand was compacted in a column and the dry density was adjusted to be 1.6 g/cm 3 . Polyacrylic acid solution (including three types of polyacrylic acid, average molecular weight 2,100, 15,000 and 450,000) was prepared and was passed through the compacted bentonite. Molecular weight distributions of polyacrylic acid in the effluent solution were analysed by GPC (Gel Permeation Chromatography). A batch type experiment was also carried out in order to examine a sorption behavior of these organic substances onto the surfaces of grains of the bentonite. The results indicated that the smaller size polyacrylic acid (molecular weight < 100,000) was passed through the compacted bentonite. On the other hand, the larger size polyacrylic acid (molecular weight ≥100,000) was mostly filtrated by the compacted bentonite. The batch type sorption tests clarified that the polyacrylic acid did not sorb onto the surfaces of minerals constituting the bentonite. Therefore it was suggested that the larger size molecules (≥100,000) of organic substances could be predominantly filtrated by the microstructure of the compacted bentonite. (author)

  9. Mineralogy and geochemistry of bauxite and bentonite deposits from Mozambique

    NARCIS (Netherlands)

    Dos Muchangos, A.C.

    2000-01-01

    Results of mineralogical and geochemical studies of bauxites, kaolinitic clays and bentoniteS from Mozambique are presented in this thesis. The bauxite and kaolinitic clay deposits in Penhalonga area (in the central western part of Mozambique) are associated with Precambrian magmatic rocks and

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

    African Journals Online (AJOL)

    2017-09-12

    ) contents of bentonite from. Tango (GT) (49.87 wt%, .... MgO. 2.08. 2.08. K. 2. O. 1.60. 1.76. TiO. 2. 0.94. 0.87. P. 2. O. 5. 1.06. 1.01. Fig 1: Chemical Compositions of the Bentonite Samples Analysed by XRF. Fourier transform ...

  11. Polypropylene–clay composite prepared from Indian bentonite

    Indian Academy of Sciences (India)

    WINTEC

    ratio, (ii) flocculated nanocomposites, for which intercalated and stacked silicate layers flocculated to some ... Malvern) and the results confirmed the distribution of the particle size in this clay. Particle size distribution of the ... Particle size distribution curve for clay, bentonite. Table 2. Chemical composition of bentonite clay.

  12. Hydrothermal alterations of Bentonites in Almeria (Spain); Alteracion hidrotermal de las bentonitas de Almeria

    Energy Technology Data Exchange (ETDEWEB)

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

    1996-12-01

    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)

  13. Vortex jamming in superconductors and granular rheology

    International Nuclear Information System (INIS)

    Yoshino, Hajime; Nogawa, Tomoaki; Kim, Bongsoo

    2009-01-01

    We demonstrate that a highly frustrated anisotropic Josephson junction array (JJA) on a square lattice exhibits a zero-temperature jamming transition, which shares much in common with those in granular systems. Anisotropy of the Josephson couplings along the horizontal and vertical directions plays roles similar to normal load or density in granular systems. We studied numerically static and dynamic response of the system against shear, i.e. injection of external electric current at zero temperature. Current-voltage curves at various strength of the anisotropy exhibit universal scaling features around the jamming point much as do the flow curves in granular rheology, shear-stress versus shear-rate. It turns out that at zero temperature the jamming transition occurs right at the isotropic coupling and anisotropic JJA behaves as exotic fragile vortex matter: it behaves as a superconductor (vortex glass) in one direction, whereas it is a normal conductor (vortex liquid) in the other direction even at zero temperature. Furthermore, we find a variant of the theoretical model for the anisotropic JJA quantitatively reproduces universal master flow-curves of the granular systems. Our results suggest an unexpected common paradigm stretching over seemingly unrelated fields-the rheology of soft materials and superconductivity.

  14. A particle-based method for granular flow simulation

    KAUST Repository

    Chang, Yuanzhang

    2012-03-16

    We present a new particle-based method for granular flow simulation. In the method, a new elastic stress term, which is derived from a modified form of the Hooke\\'s law, is included in the momentum governing equation to handle the friction of granular materials. Viscosity force is also added to simulate the dynamic friction for the purpose of smoothing the velocity field and further maintaining the simulation stability. Benefiting from the Lagrangian nature of the SPH method, large flow deformation can be well handled easily and naturally. In addition, a signed distance field is also employed to enforce the solid boundary condition. The experimental results show that the proposed method is effective and efficient for handling the flow of granular materials, and different kinds of granular behaviors can be well simulated by adjusting just one parameter. © 2012 Science China Press and Springer-Verlag Berlin Heidelberg.

  15. Geochemical processes in the Febex bentonite after a heating and hydration in situ test in the Grimsel URL

    International Nuclear Information System (INIS)

    Fernandez, A.M.; Rivas, P.; Muurinen, A.; Montarges-Pelletier, E.; Jockwer, N.

    2010-01-01

    Document available in extended abstract form only. Unsaturated compacted bentonite is foreseen by several countries as a backfill and sealing material in high-level radioactive waste repositories. The FEBEX project provides the opportunity to understand and quantify the geochemical processes taking place in the near-field and to evaluate the long-term behaviour of the FEBEX bentonite. FEBEX is a demonstration and research project, which includes a large-scale in situ experiment performed in a gallery excavated in granite at the Grimsel underground laboratory research (URL) in Switzerland. Two main operational phases have been executed: a) the First Operational Phase (1996-2002), which corresponds to the FEBEX-I and FEBEX-II projects, and b) the Second Operational Phase (2002-2007), which was carried out within the frame of the NF-PRO project. In the first Operation Phase, the in situ test consisted of: 1) the heating system formed by two heaters separated horizontally by 1 m, which simulate full-sized canisters and maintain a temperature of 100 deg. C; 2) the bentonite barrier, made of blocks of highly compacted bentonite (w.c.: 14.4%;ρ d : 1.70 g/cm 3 ); 3) the drift excavated in the granite. This rock is saturated and hydrates the clay with a water flow of 7-12 L/ day; and 4) the instrumentation, monitoring and control systems. The in situ test began on February 27 1997. Heater 1 was switched-off in February 2002. The dismantling of section 1 of the in situ test provided the opportunity to analyse the thermo-hydro-geochemical (THG) processes taking place in the bentonite barrier. In the second Operational Phase, after removing the buffer and all the components, a dummy steel cylinder with a length of 1 m was inserted in the void left by Heater 1 in the centre of the buffer. A new concrete plug with a total length of 3 m was constructed by shotcreting. Heater 2 maintained its temperature of 100 deg. C at contact with the bentonite throughout the entire

  16. Nutrient transformations during composting of pig manure with bentonite.

    Science.gov (United States)

    Li, Ronghua; Wang, Jim J; Zhang, Zengqiang; Shen, Feng; Zhang, Guangjie; Qin, Rui; Li, Xiaolong; Xiao, Ran

    2012-10-01

    This work aimed to evaluate the influence of different amounts of bentonite on nutrients transformation during pig manure composting process. The results showed that bentonite had no significant effects on compost temperature and pH changes. While, EC, moisture, OM, TN and NO(3)(-)-N were notably influenced by BT addition. The adding of BT could facilitate OM degradation, increase TKN content and decrease the C/N ratio. Increasing the proportion of bentonite in pig manure compost to reduce extractable heavy metal content is feasible. However, potherb mustard seed GI decreased with the proportion of added bentonite increasing. The results suggest that a proportion of less than 2.5% bentonite is recommended for addition to pig manure compost, and examining the additive ratio in a comprehensive waste composting project is a worthwhile direction for future research. Copyright © 2012 Elsevier Ltd. All rights reserved.

  17. The coupled process laboratory test of highly compacted bentonite

    International Nuclear Information System (INIS)

    Shen Zhenyao; Li Guoding; Li Shushen; Wang Chengzu

    2004-01-01

    Highly compacted bentonite blocks have been heated and hydrated in the laboratory in order to simulate the thermo-hydro-mechanical (THM) coupled processes of buffer material in a high-level radioactive waste (HLW) repository. The experiment facility, which is composed of experiment barrel, heated system, high pressure water input system, temperature measure system, water content measure system and swelling stress system, is introduced in this paper. The steps of the THM coupled experiment are also given out in detail. There are total 10 highly compacted bentonite blocks used in this test. Experimental number 1-4 are the tests with the heater and the hydrated process, which temperature distribution vs. time and final moisture distribution are measured. Experimental number 5-8 are the tests with the heater and without the hydrated process, which temperature distribution vs. time and final moisture distribution are measured. Experimental number 9-10 are the tests with the heater and the hydrated process, which temperature distribution vs. time, final moisture distribution and the swelling stress distribution at some typical points vs. time are measured. The maximum test time is nearly 20 days and the minimum test time is only 8 hours. The results show that the temperature field is little affected by hydration process and stress condition, but moisture transport and stress distribution are a little affected by the thermal gradient. The results also show that the water head difference is the mainly driving force of hydration process and the swelling stress is mainly from hydration process. It will great help to understand better about heat and mass transfer in porous media and the THM coupled process in actual HLW disposal. (author)

  18. Modelling interaction of deep groundwaters with bentonite and radionuclide speciation

    International Nuclear Information System (INIS)

    Wanner, H.

    1986-04-01

    In the safety analysis recently reported for a potential Swiss high-level waste repository, radionuclide speciation and solubility limits are calculated for expected granitic groundwater conditions. This report describes a thermodynamic model which is used to estimate the chemical composition of the pore water in compacted sodium bentonite. The model is based on available experimental data and describes the basic reactions between bentonite and groundwater by an ion-exchange model for sodium, potassium, magnesium, and calcium. The model assumes equilibrium with calcite as long as sufficient carbonates remain in the bentonite, as well as quartz saturation. The long-term situation is modelled by the assumption that the near-field of a deep repository behaves like a mixing tank. It is found that sodium bentonite will slowly be converted to calcium bentonite. The modelled composition of the pore water of compacted sodium bentonite is used to estimate radionuclide solubilities in the near-field of a deep repository. The elements considered are: uranium, neptunium, plutonium, thorium, americium, and technetium. The redox potential in the near-field is assumed to be controlled by the corrosion products of the iron canister. Except for uranium and neptunium, radionuclide solubilities turn out to be lower under the modelled near-field conditions than in the groundwater of the surrounding granitic host rock. Uranium and neptunium solubility might be higher by orders of magnitude in the near-field than in the far-field. From the chemical point of view, calcium bentonite seems to be more stable than sodium bentonite in the presence of Swiss Reference Groundwater. The use of calcium bentonite instead of sodium bentonite will improve the reliability in the prediction of source terms for radionuclide transport in the geosphere. (author)

  19. Long-term alteration of bentonite in the presence of metallic iron

    International Nuclear Information System (INIS)

    Kumpulainen, S.; Kiviranta, L.; Carlsson, T.; Muurinen, A.; Svensson, D.; Sasamoto, Hiroshi; Yui, Mikatzu; Wersin, P.; Rosch, D.

    2011-12-01

    According to the KBS-3H concept, each copper canister containing spent nuclear fuel will be surrounded by a bentonite buffer and a perforated steel cylinder. Since steel is unstable in wet bentonite, it will corrode and the corrosion products will interact with the surrounding bentonite in ways that are not fully understood. Such interaction may seriously impair the bentonite's functioning as a buffer material, e.g. by lowering its CEC or decreasing its swelling capacity. This report presents results from two ironbentonite experiments carried out under quite different conditions at VTT (Finland) and JAEA (Japan). Both studies focused on long-term iron-bentonite interactions under anaerobic conditions. The study at VTT comprised eight years long experiments focused on diffusive based interactions between solid cast-iron and compacted MX-80 bentonite (dry density 1.5- 1.6 g/cm 3 ) in contact with an aqueous 0.5 M NaCl solution. The study at JAEA comprised ten years long batch experiments, each involving a mixture of metallic iron powder (25 g), an industrially refined Na bentonite, Kunipia F, which contains more than 99% montmorillonite (25 g), and an aqueous solution (250 mL). Samples were sent to B and Tech in airtight steel vessels filled with N 2 and subsequently analyzed at various laboratories in Finland and Sweden. The JAEA samples differed with regard to the initial solution chemistry, which was either distilled water, 0.3 M NaCl, 0.6 M NaCl, 0.1 M NaHCO 3 , or 0.05 M Na 2 SO 4 . The analyses of the MX-80 bentonite samples were carried out on samples containing a cast iron cylinder and also on corresponding background samples with no cast iron. In addition, the external solution and gas phase in contact with the bentonite were analyzed. Briefly, the gas contained H 2 , most possibly caused by corrosion of the cast iron, and CO 2 , mainly as a result of carbonate dissolution. The eight years old external solution exhibited, inter alia, reducing conditions, a p

  20. Long-term alteration of bentonite in the presence of metallic iron

    Energy Technology Data Exchange (ETDEWEB)

    Kumpulainen, S.; Kiviranta, L. [B and Tech Oy, Helsinki (Finland); Carlsson, T.; Muurinen, A. [VTT Technical Research Centre of Finland, Espoo (Finland); Svensson, D. [Svensk Kaernbraenslehantering AB (SKB), Stockholm (Sweden); Sasamoto, Hiroshi; Yui, Mikatzu [Japan Atomic Energy Agency (JAEA) (Japan); Wersin, P.; Rosch, D. [Gruner Ltd, Basel (Switzerland)

    2011-12-15

    According to the KBS-3H concept, each copper canister containing spent nuclear fuel will be surrounded by a bentonite buffer and a perforated steel cylinder. Since steel is unstable in wet bentonite, it will corrode and the corrosion products will interact with the surrounding bentonite in ways that are not fully understood. Such interaction may seriously impair the bentonite's functioning as a buffer material, e.g. by lowering its CEC or decreasing its swelling capacity. This report presents results from two ironbentonite experiments carried out under quite different conditions at VTT (Finland) and JAEA (Japan). Both studies focused on long-term iron-bentonite interactions under anaerobic conditions. The study at VTT comprised eight years long experiments focused on diffusive based interactions between solid cast-iron and compacted MX-80 bentonite (dry density 1.5- 1.6 g/cm{sup 3}) in contact with an aqueous 0.5 M NaCl solution. The study at JAEA comprised ten years long batch experiments, each involving a mixture of metallic iron powder (25 g), an industrially refined Na bentonite, Kunipia F, which contains more than 99% montmorillonite (25 g), and an aqueous solution (250 mL). Samples were sent to B and Tech in airtight steel vessels filled with N{sub 2} and subsequently analyzed at various laboratories in Finland and Sweden. The JAEA samples differed with regard to the initial solution chemistry, which was either distilled water, 0.3 M NaCl, 0.6 M NaCl, 0.1 M NaHCO{sub 3}, or 0.05 M Na{sub 2}SO{sub 4}. The analyses of the MX-80 bentonite samples were carried out on samples containing a cast iron cylinder and also on corresponding background samples with no cast iron. In addition, the external solution and gas phase in contact with the bentonite were analyzed. Briefly, the gas contained H{sub 2}, most possibly caused by corrosion of the cast iron, and CO{sub 2}, mainly as a result of carbonate dissolution. The eight years old external solution exhibited

  1. Type-2 fuzzy granular models

    CERN Document Server

    Sanchez, Mauricio A; Castro, Juan R

    2017-01-01

    In this book, a series of granular algorithms are proposed. A nature inspired granular algorithm based on Newtonian gravitational forces is proposed. A series of methods for the formation of higher-type information granules represented by Interval Type-2 Fuzzy Sets are also shown, via multiple approaches, such as Coefficient of Variation, principle of justifiable granularity, uncertainty-based information concept, and numerical evidence based. And a fuzzy granular application comparison is given as to demonstrate the differences in how uncertainty affects the performance of fuzzy information granules.

  2. Report on hydro-mechanical and chemical-mineralogical analyses of the bentonite buffer in Canister Retrieval Test

    Energy Technology Data Exchange (ETDEWEB)

    Dueck, Ann; Johannesson, Lars-Erik; Kristensson, Ola; Olsson, Siv [Clay Technology AB (Sweden)

    2011-12-15

    The effect of five years of exposure to repository-like conditions on compacted Wyoming bentonite was determined by comparing the hydraulic, mechanical, and mineralogical properties of samples from the bentonite buffer of the Canister Retrieval Test (CRT) with those of reference material. The CRT, located at the Swedish Aspo Hard Rock Laboratory (HRL), was a full-scale field experiment simulating conditions relevant for the Swedish KBS-3 concept for disposal of high-level radioactive waste in crystalline host rock. The compacted bentonite, surrounding a copper canister equipped with heaters, had been subjected to heating at temperatures up to 95 deg C and hydration by natural Na-Ca-Cl type groundwater for almost five years at the time of retrieval. Under the thermal and hydration gradients that prevailed during the test, sulfate in the bentonite was redistributed and accumulated as anhydrite close to the canister. The major change in the exchangeable cation pool was a loss in Mg in the outer parts of the blocks, suggesting replacement of Mg mainly by Ca along with the hydration with groundwater. Close to the copper canister, small amounts of Cu were incorporated in the bentonite. A reduction of strain at failure was observed in the innermost part of the bentonite buffer, but no influence was seen on the shear strength. No change of the swelling pressure was observed, while a modest decrease in hydraulic conductivity was found for the samples with the highest densities. No coupling was found between these changes in the hydro-mechanical properties and the montmorillonite . the X-ray diffraction characteristics, the cation exchange properties, and the average crystal chemistry of the Na-converted < 1 {mu}m fractions provided no evidence of any chemical/structural changes in the montmorillonite after the 5-year hydrothermal test.

  3. Antifungal activity of streptomycetes isolated bentonite clay

    Directory of Open Access Journals (Sweden)

    V. P. Shirobokov

    2016-12-01

    Full Text Available Aim. To investigate the biological activity of streptomycetes, isolated from Ukrainian bentonite clay. Methods. For identification of the investigated microorganisms there were used generally accepted methods for study of morpho-cultural and biochemical properties and sequencing of 16Ѕ rRNA producer. Antagonistic activity of the strain was determined by agar diffusion and agar block method using gram-positive, gram-negative microorganisms and fungi. Results. Research of autochthonous flora from bentonite clay of Ukrainian various deposits proved the existence of stable politaxonomic prokaryotic-eukaryotic consortia there. It was particularly interesting that the isolated microorganisms had demonstrated clearly expressed antagonistic properties against fungi. During bacteriological investigation this bacterial culture was identified like representative of the genus Streptomyces. Bentonite streptomycetes, named as Streptomyces SVP-71, inagar mediums (agar block method inhibited the growth of fungi (yeast and mold; zones of growth retardation constituted of 11-36 mm, and did not affect the growth of bacteria. There were investigated the inhibitory effects of supernatant culture fluid, ethanol and butanol extracts of biomass streptomycetes on museum and clinical strains of fungi that are pathogenic for humans (Candida albicans, C. krusei, C. utilis, C. parapsilosis, C. tropicalis, C. kefir, S. glabrata, C. lusitaniae, Aspergillus niger, Mucor pusillus, Fusarium sporotrichioides. It has been shown that research antifungal factor had 100% of inhibitory effect against all fungi used in experiments in vitro. In parallel, it was found that alcohol extracts hadn’t influence to the growth of gram-positive and gram-negative bacteria absolutely. It was shown that the cultural fluid supernatant and alcoholic extracts of biomass had the same antagonistic effect, but with different manifestation. This evidenced about identity of antifungal substances

  4. Effect of pH to adsorption behavior of Pu on bentonite in aqueous environment

    International Nuclear Information System (INIS)

    Wang Xiaoqiang; Tuo Xianguo; Li Pingchuan; Leng Yangchun; Su Jilong; Yueping

    2013-01-01

    The effects of pH to the adsorption behavior of Pu in GMZ-bentonite, Lingshou Ca-bentonite, Na-bentonite and bleaching earth were tested by static adsorption experiments in aqueous environment. The results show that the adsorption equilibrium time of Pu is four days in GMZ-bentonite and 5-6 days in bleaching earth, Ca-bentonite and Na-bentonite. In aqueous environment, the adsorption capacity of bentonite to Pu increases with pH in water phase, and it is weak in acidic aqueous environment and strong in alkaline aqueous environment extremely. (authors)

  5. Modelling of geochemical reactions and experimental cation exchange in MX 80 bentonite.

    Science.gov (United States)

    Montes-H, G; Fritz, B; Clement, A; Michau, N

    2005-10-01

    Bentonites are widely used for waste repository systems because of their hydrodynamic, surface and chemical-retention properties. MX 80 bentonite (bentonite of Wyoming) contains approximately 85% Na/Ca-montmorillonite and 15% accessory minerals. The dominant presence of Na/Ca-montmorillonite in this clay mineral could cause it to perform exceptionally well as an engineered barrier for a radioactive waste repository because this buffer material is expected to fill up by swelling the void between canisters containing waste and the surrounding ground. However, the Na/Ca-montmorillonite could be transformed to other clay minerals as a function of time under repository conditions. Previous modelling studies based on the hydrolysis reactions have shown that the Na/Ca-montmorillonite-to-Ca-montmorillonite conversion is the most significant chemical transformation. In fact, this chemical process appears to be a simple cation exchange into the engineered barrier. The purpose of the present study was two-fold. Firstly, it was hoped to predict the newly formed products of bentonite-fluid reactions under repository conditions by applying a thermokinetic hydrochemical code (KIRMAT: Kinetic Reactions and Mass Transport). The system modelled herein was considered to consist of a 1-m thick zone of water-saturated engineered barrier. This non-equilibrated system was placed in contact with a geological fluid on one side, which was then allowed to diffuse into the barrier, while the other side was kept in contact with iron-charged water. Reducing initial conditions ( [P(O)2 approximately equals 0] ; Eh=-200 mV) and a constant reaction temperature (100 degrees C) were considered. Secondly, it was hoped to estimate the influence of inter-layer cations (Ca and Na) on the swelling behaviour of the MX 80 bentonite by using an isothermal system of water vapour adsorption and an environmental scanning electron microscope (ESEM) coupled with a digital image analysis (DIA) program. Here, the

  6. Characterization of nanocomposites containing Ecoflex®, LDPE and organophilic bentonite

    International Nuclear Information System (INIS)

    Rios, A.R.; Rosa, D.S.; Poveda, P.N.S.; Viana, H.

    2011-01-01

    Considering the need for development of environmentally degradable polymers for high performance, this study aimed to develop and characterize compounds of LDPE containing different levels of Ecoflex® (biodegradable) and organophilic bentonite (environmentally correct, low cost and plentiful). The clay showed interlayer distance (d 001 ) of 17.59 Å, which confirms the organophilization organization and salts in monolayer lateral between the layers of bentonite. Through the test IF it can be verified that the fluidity of the compounds was reduced proportionately with the addition of nano clay, improving the dimensional stability of the material. The mechanical test showed that the addition of nano clay increased the maximum stress and elastic modulus of the composites. The FTIR assay corroborated the mechanical results, indicating the presence of interfacial interactions polymer/clay, through axial deformation bands OH related to hydroxyl groups of clay. (author)

  7. Study of process variables on organophilization of Cubati-PB bentonite clays with ionic surfactants

    International Nuclear Information System (INIS)

    Silva, C.D. da; Lima, R.C.O.; Costa, J.M.R.; Silva, E.I.A.; Neves, G.A.; Ferreira, H.C.

    2012-01-01

    The organophilic clays used as agent in the composition dispersed in petroleum drilling fluids, play important roles during drilling. This work aims at the development of several varieties of smectites Cubati-PB for use in drilling fluids for oil with the use of ionic surfactants. We used the following materials: natural bentonite clay Cinza Superior and Verde Superior, from the district of Cubati-PB and ionic quaternary ammonium salt: Praepagen WB®, with 45% active matter. The organoclays were characterized by the laser diffraction, chemical composition by x-ray, differential thermal analysis, thermal gravimetric analysis and x-ray diffraction. Globally found that clays have diffraction and thermal behavior typical of bentonite clay. The results showed showed that the clay used has the potential for application in the process of organophilic and, with respect the process variables has been observed that they do not alter the process organophilization. (author)

  8. Effect of the Degree of Ionization on the Insertion of Polyvinylpyridinium Salts into Bentonite

    Directory of Open Access Journals (Sweden)

    Mohamed Amine Zenasni

    2011-01-01

    Full Text Available The present work reports the effect of the degree of α ionization of poly(4-vinylpyridinium salts (P4VPS on the insertion of these polymer salts into bentonite. Nanocomposite materials made of a Na-montmorillonite mineral with poly(4-vinylpyridinium salts (P4VPS have been synthesised and characterised. The modified samples were studied by X-ray diffraction (XRD and thermogravimetric analysis (TGA. The basic spacing of unmodified montmorillonite, determined by XRD, was measured to be 1.38 nm; it was found to increase after modification up to 1.50 nm. The insertion capacity of P4VPS into bentonite increased with the increasing degree of quaternisated nitrogen sites in the polymer.

  9. Experiments and DEM Simulations of Granular Ratcheting

    OpenAIRE

    Zorzi Gianluca; Artoni Riccardo; Gabrieli Fabio

    2017-01-01

    In this work we studied the effect of cyclic loading on a granular packing by means of numerical simulations and experiments. A confined packing of glass beads was prepared and one of the walls was moved cyclically with a prescribed amplitude of the order of the particle diameter. Different amplitudes were tested, and their effect on the free surface evolution, the force transmitted to the moving wall and the displacement patterns in the material was characterized. Discrete numerical simulati...

  10. Characteristics of undulatory locomotion in granular media

    OpenAIRE

    Peng, Zhiwei; Pak, On Shun; Elfring, Gwynn J.

    2015-01-01

    Undulatory locomotion is ubiquitous in nature and observed in different media, from the swimming of flagellated microorganisms in biological fluids, to the slithering of snakes on land, or the locomotion of sandfish lizards in sand. Despite the similarity in the undulating pattern, the swimming characteristics depend on the rheological properties of different media. Analysis of locomotion in granular materials is relatively less developed compared with fluids partially due to a lack of valida...

  11. Verification of substitution of bentonites by montmorillonitic clays summary report on Czech montmorillonitic clays

    International Nuclear Information System (INIS)

    Carlson, L.; Keto, P.

    2006-10-01

    Czech bentonites and smectite-rich clays were characterised in order to study if they could be used as buffer and backfill materials instead of non-Czech commercial bentonites. The characterisation work was orgnized by RAWRA (the Czech Radioactive Waste Repository Authority) and the main part of the work was performed in the Czech Republic at Charles University and at Czech Technical University. Parallel and complementary characterisation was conducted in Finland in Sweden. This report was compiled with the aim to summarise the results, and to compare the methods and results gained in different testing laboratories. The characterisation included mineralogical, chemical and geotechnical investigations and experiments on thermal stability and sorption. There were some variations between the results gained in different laboratories. This was mainly due to differences between the testing methods used but also due to heterogeneity of the samples. The Czech bentonite-clays from Rokle and Strance clay deposits contained relatively high amount of swelling minerals and thus can be considered as potential buffer and backfill materials. (orig.)

  12. LOT A2 Test, THC-modelling of bentonite buffer in a final repository of spent nuclear fuel

    International Nuclear Information System (INIS)

    Itaelae, A.; Olin, M.; Rasilainen, K.; Pulkkanen, V.M.

    2010-01-01

    Document available in extended abstract form only. The Finnish spent nuclear fuel disposal is planned to be based on the KBS-3V repository concept. Within this concept, the role of the bentonite buffer is considered to be central. The aim of this study was to model the evolution of the buffer during the thermal phase (heat-generating period of spent fuel), when the bentonite is only partially saturated initially, and the surrounding rock matrix is assumed to be fully saturated. It is essential to study how temperature will affect saturation and also how both of these affect the chemistry of bentonite. In order to make the modeling more concrete, an example experimental case was considered: Long Term Test of Buffer Materials (LOT) A2-parcel test at the Aespoe Hard Rock Laboratory (HRL) in Sweden. In the A2-parcel the MX-80 bentonite was exposed to adverse (120-150 deg. C) temperature conditions and high temperature gradients. The test parcel diameter was smaller than in the actual KBS-3V deposition hole to speed up the saturation. The chemical behaviour of minerals causes their redistribution inside the bentonite. For example, according to the laboratory tests, gypsum dissolves and anhydrite precipitates near the heater-bentonite interface. Also, incoming groundwater affects the bentonite pore water and its properties. These changes may, in turn, influence the mechanical properties of the bentonite. A coupled Thermo-Hydro-Chemical (THC) model was applied, which means that all mechanical effects were ignored. The purpose of the model was first to achieve a satisfactory match between the model and experimental results, and, therefore, the time frame was limited to ten years (LOT A-2 parcel test lasted approximately 6 years). The system was simplified to 1-D in order to reduce the computational work, which can be very significant due to complex chemical calculations. The 1-D model results are reported in Itaelae (2009). The aim is to extend the calculations to 2-D

  13. Granular Material Response to Dynamic Shock Compression: A Study of SiO2 in the Form of Sand and Soda Lime Glass Beads

    Science.gov (United States)

    2011-06-01

    method was used vice more accurate immersion techniques based on Archimedes principle . The initial volume of the technical sand was determined by filling...of Porous Materials In solid materials small stresses and strains are very close to being the same as the shock Hugoniot and the principle isentrope...materials are widely used for this application . For high pressures that result in full compaction of the porous material and where α is above a

  14. Kajian Adsorpsi Zat Pengatur Tumbuh Naphthalene Acetic Acid (Naa) Terhadap Bentonit Alam

    OpenAIRE

    Lailatussoimah, Nura; Artsanti, Pedy; Nugraha, Irwan

    2014-01-01

    The study of adsorption of plant growth regulators naphthalene acetic acid (NAA) by using natural bentonite aims to investigate the purification process of bentonite, determine the parameters that affect the ability of optimum adsorption and adsorption interactions of bentonite to NAA. Bentonite purification process is done by adding 30% H2O2 to oxidize organic compounds in the pores of the bentonite. Adsorption parameters in this study include the influence of the mass of adsorb...

  15. Investigations on uranium sorption on bentonite and montmorillonite, respectively, and uranium in environmental samples; Untersuchungen zur Uransorption an Bentonit bzw. Montmorillonit sowie von Uran in Umweltproben

    Energy Technology Data Exchange (ETDEWEB)

    Azeroual, Mohamed

    2010-09-22

    The geotechnical barrier is an important component of a geological repository and consists of compacted bentonite surrounding radioactive waste containers. Its most important functions are, to retard the radionuclide migration into the biosphere and to prevent groundwater contact with containers. lt is therefore of central importance to investigate the bentonite material on its capacity to sorb radionuclides under near-natural chemical and physical conditions. The purpose of this work was to study the adsorption of uranium(VI) on bentonit and on montmorillonite-standards at high uranium concentrations. Thereby, a special account was given to the calcium-uranyl-carbonate complexation, which leads to the formation of very stable and mobile uncharged Ca{sub 2}UO{sub 2}(CO{sub 3}){sub 3} complex. Results of batch experiments showed that the dicalcium-uranyl-tricarbonate complexation lowers the uranium(VI) sorption on natural clay (bentonite) by a factor of up to 3. After 21 days of contact time, about 40 % and 20 % of the initial uranium(VI)concentration were sorbed on Na-bentonite and ea-bentonite, respectively, from a solution with Ca{sub 2}UO{sub 2}(CO{sub 3}){sub 3} dominating the uranium(VI) speciation. On the contrary, about 55 % of the initial uranium(VI)-concentration were sorbed on thes clays from the solution, in which (UO{sub 2}){sub 2}CO{sub 3}(OH){sub 3}{sup -} complex dominated the uranium(VI) speciation. Thus uranium(VI) sorption is more strongly influenced by the solution composition than by bentonite type. Na-bentonite should be used instead of ea-bentonite as a geotechnical barrier, since calcium-uranyl-carbonate complexation may be a realistic scenario. Further SEM-EDX and HREM-EDX studies showed that uranium(VI) sorption occurred predominantly on montmorillonite, which is the main component of bentonite. Uranium(VI) sorption on bentonite's accessory Minerals (pyrite, calcite, mica, and feldspar) was not observed. Investigation of uranium

  16. Granular flow over inclined channels with constrictions

    Science.gov (United States)

    Tunuguntla, Deepak; Weinhart, Thomas; Thornton, Anthony; Bokhove, Onno

    2013-04-01

    , investigate the channel formed by the dead zones and compare it with our analytical calculations. REFERENCES 1. Akers, B. & Bokhove, O. 2008 Hydraulic flow through a channel contraction: Multiple steady states. Physics of fluids 20 (056601), 056601. 2. Mercury 2010 http://www2.msm.ctw.utwente.nl/athornton/md/ . 3. Pesch, L., Bell, A., Sollie, H., Ambati, V.R., Bokhove, O. & Van der Vegt, J.J.W. 2007 hpGEM—a software framework for discontinuous Galerkin finite element methods. ACM Transactions on Mathematical Software (TOMS) 33 (4), 23. 4. Savage, SB & Hutter, K. 1989 The motion of a finite mass of granular material down a rough incline. Journal of Fluid Mechanics 199 (1), 177-215. 5. Vreman, AW, Al-Tarazi, M., Kuipers, JAM, van Sint Annaland, M. & Bokhove, O. 2007 Supercritical shallow granular flow through a contraction: experiment, theory and simulation. Journal of Fluid Mechanics 578 (1), 233-269. 6. Weinhart, T., Thornton, A.R., Luding, S. & Bokhove, O. 2012 Closure relations for shallow granular flows from particle simulations. Granular Matter 14 (4), 531-552.

  17. Thermo-hydro-mechanical characterisation and modelling of MX-80 granular bentonite

    Energy Technology Data Exchange (ETDEWEB)

    Seiphoori, A.

    2014-07-01

    The library of the Swiss Federal Institute of Technology EPFL does not publish an abstract for this thesis. Accordingly, no abstract can be made available by INIS. However, the EPFL library will send the full text of the thesis, free of charge, to anybody asking for it. Please use the indicated DOI to contact the library.

  18. Engineering Properties of Bentonite Stabilized with Lime and Phosphogypsum

    Science.gov (United States)

    Kumar, Sujeet; Dutta, Rakesh Kumar; Mohanty, Bijayananda

    2014-12-01

    Engineering properties such as compaction, unconfined compressive strength, consistency limits, percentage swell, free swell index, the California bearing ratio and the consolidation of bentonite stabilized with lime and phosphogypsum are presented in this paper. The content of the lime and phosphogypsum varied from 0 to 10 %. The results reveal that the dry unit weight and optimum moisture content of bentonite + 8 % lime increased with the addition of 8 % phosphogypsum. The percentage of swell increased and the free swell index decreased with the addition of 8 % phosphogypsum to the bentonite + 8 % lime mix. The unconfined compressive strength of the bentonite + 8 % lime increased with the addition of 8 % phosphogypsum as well as an increase in the curing period up to 14 days. The liquid limit and plastic limit of the bentonite + 8 % lime increased, whereas the plasticity index remained constant with the addition of 8 % phosphogypsum. The California bearing ratio, modulus of subgrade reaction, and secant modulus increased for the bentonite stabilized with lime and phosphogypsum. The coefficient of the consolidation of the bentonite increased with the addition of 8 % lime and no change with the addition of 8 % phosphogypsum.

  19. Engineering Properties of Bentonite Stabilized with Lime and Phosphogypsum

    Directory of Open Access Journals (Sweden)

    Kumar Sujeet

    2014-12-01

    Full Text Available Engineering properties such as compaction, unconfined compressive strength, consistency limits, percentage swell, free swell index, the California bearing ratio and the consolidation of bentonite stabilized with lime and phosphogypsum are presented in this paper. The content of the lime and pho