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Sample records for unsaturated rock fractures

  1. CAPILLARY BARRIERS IN UNSATURATED FRACTURED ROCKS OF YUCCA MOUNTAIN, NEVADA

    International Nuclear Information System (INIS)

    Wu, Y.S.; Zhang, W.; Pan, L.; Hinds, J.; Bodvarsson, G.

    2000-01-01

    This work presents modeling studies investigating the effects of capillary barriers on fluid-flow and tracer-transport processes in the unsaturated zone of Yucca Mountain, Nevada, a potential site for storing high-level radioactive waste. These studies are designed to identify factors controlling the formation of capillary barriers and to estimate their effects on the extent of possible large-scale lateral flow in unsaturated fracture rocks. The modeling approach is based on a continuum formulation of coupled multiphase fluid and tracer transport through fractured porous rock. Flow processes in fractured porous rock are described using a dual-continuum concept. In addition, approximate analytical solutions are developed and used for assessing capillary-barrier effects in fractured rocks. This study indicates that under the current hydrogeologic conceptualization of Yucca Mountain, strong capillary-barrier effects exist for significantly diverting moisture flow

  2. Effective media models for unsaturated fractured rock: A field experiment

    International Nuclear Information System (INIS)

    Nicholl, M.J.; Glass, R.J.

    1995-01-01

    A thick unsaturated rock mass at Yucca Mountain is currently under consideration as a potential repository site for disposal of high level radioactive waste. In accordance with standard industry and scientific practices, abstract numerical models will be used to evaluate the potential for radionuclide release through the groundwater system. At this time, currently available conceptual models used to develop effective media properties are based primarily on simplistic considerations. The work presented here is part of an integrated effort to develop effective media models at the intermediate block scale (approximately 8-125m) through a combination of physical observations, numerical simulations and theoretical considerations. A multi-purpose field experiment designed and conducted as part of this integrated effort is described. Specific goals of this experimental investigation were to: (1) obtain fracture network data from Topopah Spring Tuff for use in block scale simulations; (2) identity positions of the network conducting flow under three different boundary conditions; (3) visualize preferential flow paths and small-scale flow structures; (4) collect samples for subsequent hydraulic testing and use in block-scale simulations; and (5) demonstrate the ability of Electrical Resistance Tomography (ERT) to delineate fluid distribution within fractured rock

  3. Radionuclide transport as vapor through unsaturated fractured rock

    International Nuclear Information System (INIS)

    Green, R.T.

    1986-01-01

    The objective of this study is to identify and examine potential mechanisms of radionuclide transport as vapor at a high-level radioactive waste repository located in unsaturated fractured rock. Transport mechanisms and processes have been investigated near the repository and at larger distances. Transport mechanisms potentially important at larger distances include ordinary diffusion, viscous flow and free convection. Ordinary diffusion includes self and binary diffusion, Knudsen flow and surface diffusion. Pressure flow and slip flow comprise viscous flow. Free convective flow results from a gas density contrast. Transport mechanisms or processes dominant near the repository include ordinary diffusion, viscous flow plus several mechanisms whose driving forces arise from the non-isothermal, radioactive nature of high-level waste. The additional mechanisms include forced diffusion, aerosol transport, thermal diffusion and thermophoresis. Near a repository vapor transport mechanisms and processes can provide a significant means of transport from a failed canister to the geologic medium from which other processes can transport radionuclides to the accessible environment. These issues are believed to be important factors that must be addressed in the assessment of specific engineering designs and site selection of any proposed HLW repository

  4. Seepage into drifts in unsaturated fractured rock at Yucca Mountain

    International Nuclear Information System (INIS)

    Birkholzer, Jens; Li, Guomin; Tsang, Chin-Fu; Tsang, Yvonne

    1998-01-01

    An important issue for the long-term performance of underground nuclear waste repository is the rate of seepage into the waste emplacement drifts. A prediction of the future seepage rate is particularly complicated for the potential repository site at Yucca Mountain, Nevada, as it is located in thick, partially saturated, fractured tuff formations. The long-term situation in the drifts several thousand years after waste emplacement will be characterized by a relative humidity level close to or equal to 100%, as the drifts will be sealed and unventilated, and the waste packages will have cooled. The underground tunnels will then act as capillary barriers for the unsaturated flow, ideally diverting water around them, if the capillary forces are stronger than gravity and viscous forces. Seepage into the drifts will only be possible if the hydraulic pressure in the rock close to the drift walls increases to positive values; i.e., the flow field becomes locally saturated. In the present work, they have developed and applied a methodology to study the potential rate of seepage into underground cavities embedded in a variably saturated, heterogeneous fractured rock formation. The fractured rock mass is represented as a stochastic continuum where the fracture permeabilities vary by several orders of magnitude. Three different realizations of random fracture permeability fields are generated, with the random permeability structure based on extensive fracture mapping, borehole video analysis, and in-situ air permeability testing. A 3-D numerical model is used to simulate the heterogeneous steady-state flow field around the drift, with the drift geometry explicitly represented within the numerical discretization grid. A variety of flow scenarios are considered assuming present-day and future climate conditions at Yucca Mountain. The numerical study is complemented by theoretical evaluations of the drift seepage problem, using stochastic perturbation theory to develop a better

  5. Estimation of hydrologic properties of an unsaturated, fractured rock mass

    International Nuclear Information System (INIS)

    Klavetter, E.A.; Peters, R.R.

    1986-07-01

    In this document, two distinctly different approaches are used to develop continuum models to evaluate water movement in a fractured rock mass. Both models provide methods for estimating rock-mass hydrologic properties. Comparisons made over a range of different tuff properties show good qualitative and quantitative agreement between estimates of rock-mass hydrologic properties made by the two models. This document presents a general discussion of: (1) the hydrology of Yucca Mountain, and the conceptual hydrological model currently being used for the Yucca Mountain site, (2) the development of two models that may be used to estimate the hydrologic properties of a fractured, porous rock mass, and (3) a comparison of the hydrologic properties estimated by these two models. Although the models were developed in response to hydrologic characterization requirements at Yucca Mountain, they can be applied to water movement in any fractured rock mass that satisfies the given assumptions

  6. Research program to develop and validate conceptual models for flow and transport through unsaturated, fractured rock

    International Nuclear Information System (INIS)

    Glass, R.J.; Tidwell, V.C.

    1991-09-01

    As part of the Yucca Mountain Project, our research program to develop and validate conceptual models for flow and transport through unsaturated fractured rock integrates fundamental physical experimentation with conceptual model formulation and mathematical modeling. Our research is directed toward developing and validating macroscopic, continuum-based models and supporting effective property models because of their widespread utility within the context of this project. Success relative to the development and validation of effective property models is predicted on a firm understanding of the basic physics governing flow through fractured media, specifically in the areas of unsaturated flow and transport in a single fracture and fracture-matrix interaction

  7. Research program to develop and validate conceptual models for flow and transport through unsaturated, fractured rock

    International Nuclear Information System (INIS)

    Glass, R.J.; Tidwell, V.C.

    1991-01-01

    As part of the Yucca Mountain Project, our research program to develop and validate conceptual models for flow and transport through unsaturated fractured rock integrates fundamental physical experimentation with conceptual model formulation and mathematical modeling. Our research is directed toward developing and validating macroscopic, continuum-based models and supporting effective property models because of their widespread utility within the context of this project. Success relative to the development and validation of effective property models is predicated on a firm understanding of the basic physics governing flow through fractured media, specifically in the areas of unsaturated flow and transport in a single fracture and fracture-matrix interaction. 43 refs

  8. Research program to develop and validate conceptual models for flow and transport through unsaturated, fractured rock

    International Nuclear Information System (INIS)

    Glass, R.J.; Tidwell, V.C.

    1991-01-01

    As part of the Yucca Mountain Project, our research program to develop and validate conceptual models for flow and transport through unsaturated fractured rock integrates fundamental physical experimentation with conceptual model formulation and mathematical modeling. Our research is directed toward developing and validating macroscopic, continuum-based models and supporting effective property models because of their widespread utility within the context of this project. Success relative to the development and validation of effective property models is predicted on a firm understanding of the basic physics governing flow through fractured media, specifically in the areas of unsaturated flow and transport in a single fracture and fracture-matrix interaction

  9. Semi-analytical treatment of fracture/matrix flow in a dual-porosity simulator for unsaturated fractured rock masses

    International Nuclear Information System (INIS)

    Zimmerman, R.W.; Bodvarsson, G.S.

    1992-04-01

    A semi-analytical dual-porosity simulator for unsaturated flow in fractured rock masses has been developed. Fluid flow between the fracture network and the matrix blocks is described by analytical expressions that have been derived from approximate solutions to the imbibition equation. These expressions have been programmed into the unsaturated flow simulator, TOUGH, as a source/sink term. Flow processes are then simulated using only fracture elements in the computational grid. The modified code is used to simulate flow along single fractures, and infiltration into pervasively fractured formations

  10. Continuum model for water movement in an unsaturated fractured rock mass

    International Nuclear Information System (INIS)

    Peters, R.R.; Klavetter, E.A.

    1988-01-01

    The movement of fluids in a fractured, porous medium has been the subject of considerable study. This paper presents a continuum model that may be used to evaluate the isothermal movement of water in an unsaturated, fractured, porous medium under slowly changing conditions. This continuum model was developed for use in evaluating the unsaturated zone at the Yucca Mountain site as a potential repository for high-level nuclear waste. Thus its development has been influenced by the conditions thought to be present at Yucca Mountain. A macroscopic approach and a microscopic approach are used to develop a continuum model to evaluate water movement in a fractured rock mass. Both approaches assume that the pressure head in the fractures and the matrix are identical in a plane perpendicular to flow. Both approaches lead to a single-flow equation for a fractured rock mass. The two approaches are used to calculate unsaturated hydrologic properties, i.e., relative permeability and saturation as a function of pressure head, for several types of tuff underlying Yucca Mountain, using the best available hydrologic data for the matrix and the fractures. Rock mass properties calculated by both approaches are similar

  11. Analyzing Unsaturated Flow Patterns in Fractured Rock Using an Integrated Modeling Approach

    International Nuclear Information System (INIS)

    Y.S. Wu; G. Lu; K. Zhang; L. Pan; G.S. Bodvarsson

    2006-01-01

    Characterizing percolation patterns in unsaturated fractured rock has posed a greater challenge to modeling investigations than comparable saturated zone studies, because of the heterogeneous nature of unsaturated media and the great number of variables impacting unsaturated flow. This paper presents an integrated modeling methodology for quantitatively characterizing percolation patterns in the unsaturated zone of Yucca Mountain, Nevada, a proposed underground repository site for storing high-level radioactive waste. The modeling approach integrates a wide variety of moisture, pneumatic, thermal, and isotopic geochemical field data into a comprehensive three-dimensional numerical model for modeling analyses. It takes into account the coupled processes of fluid and heat flow and chemical isotopic transport in Yucca Mountain's highly heterogeneous, unsaturated fractured tuffs. Modeling results are examined against different types of field-measured data and then used to evaluate different hydrogeological conceptualizations and their results of flow patterns in the unsaturated zone. In particular, this model provides a much clearer understanding of percolation patterns and flow behavior through the unsaturated zone, both crucial issues in assessing repository performance. The integrated approach for quantifying Yucca Mountain's flow system is demonstrated to provide a practical modeling tool for characterizing flow and transport processes in complex subsurface systems

  12. Coupled hydrological-mechanical effects due to excavation of underground openings in unsaturated fractured rocks

    International Nuclear Information System (INIS)

    Montazer, P.

    1985-01-01

    One of the effects of excavating an underground opening in fractured rocks is a modification of the state of the stress in the rock mass in the vicinity of the opening. This effect causes changes in the geometry of the cross sections of the fracture planes, which in turn results in modification of the hydrologic properties of the fractures of the rock mass. The significance of the orientation of the fractures and their stiffness on the extent of the modification of the hydrologic properties as a result of excavation of underground openings is demonstrated. A conceptual model is presented to illustrate the complexity of the coupled hydrological-mechanical phenomena in the unsaturated zone. This conceptual model is used to develop an investigative program to assess the extent of the effect at a proposed repository site for storing high-level nuclear wastes

  13. Unsaturated flow and transport through fractured rock related to high-level waste repositories

    International Nuclear Information System (INIS)

    Evans, D.D.; Rasmussen, T.C.

    1991-01-01

    Research results are summarized for a US Nuclear Regulatory Commission contract with the University of Arizona focusing on field and laboratory methods for characterizing unsaturated fluid flow and solute transport related to high-level radioactive waste repositories. Characterization activities are presented for the Apache Leap Tuff field site. The field site is located in unsaturated, fractured tuff in central Arizona. Hydraulic, pneumatic, and thermal characteristics of the tuff are summarized, along with methodologies employed to monitor and sample hydrologic and geochemical processes at the field site. Thermohydrologic experiments are reported which provide laboratory and field data related to the effects conditions and flow and transport in unsaturated, fractured rock. 29 refs., 17 figs., 21 tabs

  14. Validation studies for assessing unsaturated flow and transport through fractured rock

    International Nuclear Information System (INIS)

    Bassett, R.L.; Neuman, S.P.; Rasmussen, T.C.; Guzman, A.; Davidson, G.R.; Lohrstorfer, C.F.

    1994-08-01

    *The objectives of this contract are to examine hypotheses and conceptual models concerning unsaturated flow and transport through heterogeneous fractured rock and to design and execute confirmatory field and laboratory experiments to test these hypotheses and conceptual models. Important new information is presented such as the application and evaluation of procedures for estimating hydraulic, pneumatic, and solute transport coefficients for a range of thermal regimes. A field heater experiment was designed that focused on identifying the suitability of existing monitoring equipment to obtain required data. A reliable method was developed for conducting and interpreting tests for air permeability using a straddle-packer arrangement. Detailed studies of fracture flow from Queen Creek into the Magina Copper Company ore haulage tunnel have been initiated. These studies will provide data on travel time for transport of water and solute in unsaturated tuff. The collection of rainfall runoff, and infiltration data at two small watersheds at the Apache Leap Tuff Site enabled us to evaluate the quantity and rate of water infiltrating into the subsurface via either fractures or matrix. Characterization methods for hydraulic parameters relevant to Weigh-level waste transport, including fracture apertures, transmissivity, matrix porosity, and fracture wetting front propagation velocities, were developed

  15. Validation studies for assessing unsaturated flow and transport through fractured rock

    Energy Technology Data Exchange (ETDEWEB)

    Bassett, R.L.; Neuman, S.P.; Rasmussen, T.C.; Guzman, A.; Davidson, G.R.; Lohrstorfer, C.F. [Arizona Univ., Tucson, AZ (United States). Dept. of Hydrology and Water Resources

    1994-08-01

    *The objectives of this contract are to examine hypotheses and conceptual models concerning unsaturated flow and transport through heterogeneous fractured rock and to design and execute confirmatory field and laboratory experiments to test these hypotheses and conceptual models. Important new information is presented such as the application and evaluation of procedures for estimating hydraulic, pneumatic, and solute transport coefficients for a range of thermal regimes. A field heater experiment was designed that focused on identifying the suitability of existing monitoring equipment to obtain required data. A reliable method was developed for conducting and interpreting tests for air permeability using a straddle-packer arrangement. Detailed studies of fracture flow from Queen Creek into the Magina Copper Company ore haulage tunnel have been initiated. These studies will provide data on travel time for transport of water and solute in unsaturated tuff. The collection of rainfall runoff, and infiltration data at two small watersheds at the Apache Leap Tuff Site enabled us to evaluate the quantity and rate of water infiltrating into the subsurface via either fractures or matrix. Characterization methods for hydraulic parameters relevant to Weigh-level waste transport, including fracture apertures, transmissivity, matrix porosity, and fracture wetting front propagation velocities, were developed.

  16. Numerical simulation of gas flow through unsaturated fractured rock at Yucca Mountain, Nevada

    International Nuclear Information System (INIS)

    Cooper, C.A.

    1990-01-01

    Numerical analysis is used to identify the physical phenomena associated with barometrically driven gas (air and water vapor) flow through unsaturated fractured rock at Yucca Mountain, Nevada. Results from simple finite difference simulations indicate that for a fractured rock scenario, the maximum velocity of air out of an uncased 10 cm borehole is 0.002 m s -1 . An equivalent porous medium (EPM) model was incorporated into a multiphase, multicomponent simulator to test more complex conceptual models. Results indicate that for a typical June day, a diurnal pressure wave propagates about 160 m into the surrounding Tiva Canyon hydrogeologic unit. Dry air that enters the formation evaporates water around the borehole which reduces capillary pressure. Multiphase countercurrent flow develops in the vicinity of the hole; the gas phase flows into the formation while the liquid phase flows toward the borehole. The effect occurs within 0.5 m of the borehole. The amount of water vapor leaving the formation during 1 day is 900 cm 3 . This is less than 0.1% of the total recharge into the formation, suggesting that the barometric effect may be insignificant in drying the unsaturated zone. However, gas phase velocities out of the borehole (3 m s -1 ), indicating that observed flow rates from wells along the east flank of Yucca Mountain were able to be simulated with a barometric model

  17. Determination of Transport Properties From Flowing Fluid Temperature Logging In Unsaturated Fractured Rocks: Theory And Semi-Analytical Solution

    International Nuclear Information System (INIS)

    Mukhopadhyay, Sumit; Tsang, Yvonne W.

    2008-01-01

    Flowing fluid temperature logging (FFTL) has been recently proposed as a method to locate flowing fractures. We argue that FFTL, backed up by data from high-precision distributed temperature sensors, can be a useful tool in locating flowing fractures and in estimating the transport properties of unsaturated fractured rocks. We have developed the theoretical background needed to analyze data from FFTL. In this paper, we present a simplified conceptualization of FFTL in unsaturated fractured rock, and develop a semianalytical solution for spatial and temporal variations of pressure and temperature inside a borehole in response to an applied perturbation (pumping of air from the borehole). We compare the semi-analytical solution with predictions from the TOUGH2 numerical simulator. Based on the semi-analytical solution, we propose a method to estimate the permeability of the fracture continuum surrounding the borehole. Using this proposed method, we estimated the effective fracture continuum permeability of the unsaturated rock hosting the Drift Scale Test (DST) at Yucca Mountain, Nevada. Our estimate compares well with previous independent estimates for fracture permeability of the DST host rock. The conceptual model of FFTL presented in this paper is based on the assumptions of single-phase flow, convection-only heat transfer, and negligible change in system state of the rock formation. In a sequel paper (Mukhopadhyay et al., 2008), we extend the conceptual model to evaluate some of these assumptions. We also perform inverse modeling of FFTL data to estimate, in addition to permeability, other transport parameters (such as porosity and thermal conductivity) of unsaturated fractured rocks

  18. Seepage into an Underground Opening Constructed in Unsaturated Fractured Rock Under Evaporative Conditions, RPR 29013(C)

    International Nuclear Information System (INIS)

    Trautz, R. C.; Wang, Joseph S. Y.

    2001-01-01

    Liquid-release tests, performed in boreholes above an underground opening constructed in unsaturated fractured rock, are used in this study to evaluate seepage into a waste emplacement drift. Evidence for the existence of a capillary barrier at the ceiling of the drift is presented, based on field observations (including spreading of the wetting front across the ceiling and water movement up fractures exposed in the ceiling before seepage begins). The capillary barrier mechanism has the potential to divert water around the opening, resulting in no seepage when the percolation flux is at or below the seepage threshold flux. Liquid-release tests are used to demonstrate that a seepage threshold exists and to measure the magnitude of the seepage threshold flux for three test zones that seeped. The seepage data are interpreted using analytical techniques to estimate the test-specific strength of the rock capillary forces (α -1 ) that prevent water from seeping into the drift. Evaporation increases the seepage threshold flux making it more difficult for water to seep into the drift and producing artificially inflated α -1 values. With adjustments for evaporation, the minimum test-specific threshold is 1,600 mm/yr with a corresponding α -1 of 0.027 m

  19. A Modeling Study of Flow Diversion and Focusing in unsaturated Fractured Rocks

    International Nuclear Information System (INIS)

    Pan, Lehua; Wu, Yu-Shu; Zhang, Keni

    2002-01-01

    This study presents a systematic approach to analyze the flow diversion and flow focusing caused by the natural flow-barrier system in the unsaturated zone (UZ) of Yucca Mountain, Nevada, under ambient steady-state flow conditions. An existing analytical solution for analyzing capillary barrier in porous media has been extended to apply to the fractured porous rock. The new analytical solutions are used to identify the critical layers and to provide the guidance for generation of a proper three-dimensional (3-D), site-scale numerical grid. A large-scale 3-D numerical model (with more than a million grid blocks) has been developed with site-specific data to analyze the major flow patterns in the mountain. Our analyses show that large-scale lateral flow could take place in the UZ under ambient conditions, as a result of capillary barriers formed at the contacts of heterogeneous rock layers. This lateral flow runs generally toward the east (in the southern part) or southeast (in the northern part), which is consistent with the dip of the layer contacts. About 90 percent of the total lateral flow is found to be conducted by only a few critical rock layers. Faults that penetrate these rock layers act as vertical capillary barriers that stop the lateral flow. The combined effect of horizontal and vertical capillary barriers resulted in reduced percolation flow through repository horizon in general but focused downward flow along those penetrating faults. The model results were found to be consistent with the field water saturation. The findings of this study are consistent with a previously published two-dimensional (2-D) analysis and recent published modeling results using field-observed Cl-data

  20. Proceedings of workshop 5: Flow and transport through unsaturated fractured rock -- related to high-level radioactive waste disposal

    International Nuclear Information System (INIS)

    Evans, D.D.; Nicholson, T.J.

    1993-06-01

    The ''Workshop on Flow and Transport Through Unsaturated Fractured Rock Related to High-Level Radioactive Waste Disposal'' was cosponsored by the NRC, the Center for Nuclear Waste Regulatory Analyses, and the University of Arizona (UAZ) and was held in Tucson, Arizona, on January 7--10, 1991. The focus of this workshop, similar to the earlier four (the first being in 1982), related to hydrogeologic technical issues associated with possible disposal of commercial high-level nuclear waste (HLW) in a geologic repository within an unsaturated fractured rock system which coincides with the UAZ field studies on HLW disposal. The presentations and discussions centered on flow and transport processes and conditions, relevant parameters, as well as state-of-the-art measurement techniques, and modeling capabilities. The workshop consisted of: four half-day technical meetings, a one day field visit to the Apache Leap test site to review ongoing field studies that are examining site characterization techniques and developing data sets for model validation studies, and a final half-day session devoted to examining research needs related to modeling groundwater flow and radionuclide transport in unsaturated, fractured rock. These proceedings provide extended abstracts of the technical presentations and short summaries of the research group reports

  1. Flow and transport in unsaturated fractured rock: Effects of multiscale heterogeneity of hydrogeologic properties

    International Nuclear Information System (INIS)

    Zhou, Quanlin; Liu, Hui-Hai; Bodvarsson, Gudmundur S.; Oldenburg, Curtis M.

    2002-01-01

    The heterogeneity of hydrogeologic properties at different scales may have different effects on flow and transport processes in a subsurface system. A model for the unsaturated zone of Yucca Mountain, Nevada, is developed to represent complex heterogeneity at two different scales: (1) layer scale corresponding to geologic layering and (2) local scale. The layer-scale hydrogeologic properties are obtained using inverse modeling, based on the available measurements collected from the Yucca Mountain site. Calibration results show a significant lateral and vertical variability in matrix and fracture properties. Hydrogeologic property distributions in a two-dimensional, vertical cross section of the site are generated by combining the average layer-scale matrix and fracture properties with local-scale perturbations generated using a stochastic simulation method. The unsaturated water flow and conservative (nonsorbing) tracer transport through the cross section are simulated for different sets of matrix and fracture property fields. Comparison of simulation results indicates that the local-scale heterogeneity of matrix and fracture properties has a considerable effect on unsaturated flow processes, leading to fast flow paths in fractures and the matrix. These paths shorten the travel time of a conservative tracer from the source (repository) horizon in the unsaturated zone to the water table for small fractions of total released tracer mass. As a result, the local-scale heterogeneity also has a noticeable effect on global tracer transport processes, characterized by an average breakthrough curve at the water table, especially at the early arrival time of tracer mass. However, the effect is not significant at the later time after 20 percent tracer mass reaches the water table. The simulation results also verify that matrix diffusion plays an important role in overall solute transport processes in the unsaturated zone at Yucca Mountain

  2. Numerical modeling of isothermal and nonisothermal flow in unsaturated fractured rock: A review

    International Nuclear Information System (INIS)

    Pruess, K.; Wang, J.S.Y.

    1986-01-01

    The tuff formations at and near the Nevada Test Site are comprised of fractured-porous material, with hydrologic properties quite different from those encountered in most previous unsaturated flow studies dealing with soils. In the vicinity of the waste packages, flow is driven by high temperatures (exceeding 100 0 C) and large temperature gradients. The approximations developed in soil science for weakly nonisothermal flow are not applicable to this situation, and a multiphase description of flow is required, similar to approaches used in modeling of geothermal reservoirs and thermally enhance oil recovery. The conventional approach to unsaturated flow is applicable, however, to a variety of problems relating to natural (undisturbed) and far-field flow conditions. This paper reviews recent work on numerical modeling of unsaturated flow undertaken in the context of nuclear waste isolation studies. Concepts and applications of broader interest are summarized, and important issues are identified that have not been adequately explored. 84 refs, 8 figs

  3. Challenging and improving conceptual models for isothermal flow in unsaturated, fractured rock through exploration of small-scale processes

    International Nuclear Information System (INIS)

    Glass, R.J.; Nicholl, M.J.; Tidwell, V.C.

    1996-01-01

    Over the past several years, the authors have performed experimental studies focused on understanding small-scale flow processes within discrete fractures and individual matrix blocks; much of the understanding gained in that time differs from that underlying the basic assumptions used in effective media representations. Here they synthesize the process level understanding gained from their laboratory studies to explore how such small-scale processes may influence the behavior of fluid flow in fracture networks and ensembles of matrix blocks at levels sufficient to impact the formulation of intermediate-scale effective media properties. They also explore, by means of a thought experiment, how these same small-scale processes could couple to produce a large-scale system response inconsistent with current conceptual models based on continuum representations of flow through unsaturated, fractured rock. Based on their findings, a number of modifications to existing dual permeability models are suggested that should allow them improved applicability; however, even with these modifications, it is likely that continuum representations of flow through unsaturated fractured rock will have limited validity and must therefore be applied with caution

  4. MODELING COUPLED PROCESSES OF MULTIPHASE FLOW AND HEAT TRANSFER IN UNSATURATED FRACTURED ROCK

    International Nuclear Information System (INIS)

    Y. Wu; S. Mukhopadhyay; K. Zhang; G.S. Bodvarsson

    2006-01-01

    A mountain-scale, thermal-hydrologic (TH) numerical model is developed for investigating unsaturated flow behavior in response to decay heat from the radioactive waste repository at Yucca Mountain, Nevada, USA. The TH model, consisting of three-dimensional (3-D) representations of the unsaturated zone, is based on the current repository design, drift layout, and thermal loading scenario under estimated current and future climate conditions. More specifically, the TH model implements the current geological framework and hydrogeological conceptual models, and incorporates the most updated, best-estimated input parameters. This mountain-scale TH model simulates the coupled TH processes related to mountain-scale multiphase fluid flow, and evaluates the impact of radioactive waste heat on the hydrogeological system, including thermally perturbed liquid saturation, gas- and liquid-phase fluxes, and water and rock temperature elevations, as well as the changes in water flux driven by evaporation/condensation processes and drainage between drifts. For a better description of the ambient geothermal condition of the unsaturated zone system, the TH model is first calibrated against measured borehole temperature data. The ambient temperature calibration provides the necessary surface and water table boundary as well as initial conditions. Then, the TH model is used to obtain scientific understanding of TH processes in the Yucca Mountain unsaturated zone under the designed schedule of repository thermal load

  5. Coupled thermohydromechanical analysis of a heater test in unsaturated clay and fractured rock at Kamaishi Mine. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Rutqvist, J.; Noorishad, J.; Tsang, C.F. [Lawrence Berkeley National Lab., Berkeley, CA (United States). Earth Sciences Division

    1999-08-01

    The recent interest in coupled thermohydromechanical (THM) processes associated with geological disposal of spent nuclear fuel, and in particular the issue of resaturation of a clay buffer around a waste canister, has encouraged major development of the finite element computer program ROCMAS in the past three years. The main objective is to develop a tool for analysis of THM processes in practical field scale, including fractured rock masses and detailed behavior of the near-field, nonisothermal and unsaturated system composed of rock fractures and clay buffer. In this report, the ROCMAS code is presented and applied for modeling of coupled THM processes in small laboratory samples of bentonite clay as well as a large in situ THM experiment in fractured rocks, at Kamaishi Mine, Japan. The fundamental responses of a bentonite clay material were investigated in a number of laboratory tests, including suction tests, infiltration tests, thermal gradient tests, and swelling pressure tests. These laboratory tests are modeled with ROCMAS for determination of material properties and for validation of the newly implemented algorithms. The ROCMAS code is also applied for modeling of a 3-year in situ heater experiment conducted in fractured hard rock, which consists of a heater-clay buffer system and simulates a nuclear waste repository. The temperature of the heater was set to 100 deg C during 8.5 months followed by a 6-month cooling period. The bentonite and the rock surrounding the heater were extensively instrumented for monitoring of temperature, moisture content, fluid pressure, stress, strain, and displacements. An overall good agreement between the modeling and measured results, both against the laboratory experiments and the in situ heater test, indicates that the THM responses in fractured rock and bentonite are well represented by the coupled numerical model, ROCMAS. In addition, robustness and applicability of ROCMAS to practical scale problems is demonstrated

  6. Characterization of Spatial Variability of Hydrogeologic Properties for Unsaturated Flow in the Fractured Rocks at Yucca Mountain, Nevada

    International Nuclear Information System (INIS)

    Zhou, Quanlin; Bodvarsson, Gudmundur S.; Liu, Hui-Hai; Oldenburg, Curtis M.

    2002-01-01

    The spatial variability of layer-scale hydrogeologic properties of the unsaturated zone (UZ) at Yucca Mountain, Nevada, is investigated using inverse modeling. The thick UZ is grouped into five hydrostratigraphic units and further into 35 hydrogeologic layers. For each layer, lateral variability is represented by the variations in calibrated values of layer-scale properties at different individual deep boreholes. In the calibration model, matrix and fracture properties are calibrated for the one-dimensional vertical column at each individual borehole using the ITOUGH2 code. The objective function is the summation of the weighted misfits between the ambient unsaturated flow (represented by measured state variables: water saturation, water potential, and pneumatic pressure) and the simulated one in the one-dimensional flow system. The objective function also includes the weighted misfits between the calibrated properties and their prior information. Layer-scale state variables and prior rock properties are obtained from their core-scale measurements. Because of limited data, the lateral variability of three most sensitive properties (matrix permeability, matrix of the van Genuchten characterization, and fracture permeability) is calibrated, while all other properties are fixed at their calibrated layer-averaged values. Considerable lateral variability of hydrogeologic properties is obtained. For example, the lateral variability of is two to three orders of magnitude and that of and is one order of magnitude. The effect of lateral variability on site-scale flow and transport will be investigated in a future study

  7. An evaluation of the active fracture concept with modeling unsaturated flow and transport in a fractured meter-sized block of rock

    International Nuclear Information System (INIS)

    Seol, Yongkoo; Kneafsey, Timothy J.; Ito, Kazumasa

    2003-01-01

    Numerical simulation is an effective and economical tool for optimally designing laboratory experiments and deriving practical experimental conditions. We executed a detailed numerical simulation study to examine the active fracture concept (AFC, Liu et al., 1998) using a cubic meter-sized block model. The numerical simulations for this study were performed by applying various experimental conditions, including different bottom flow boundaries, varying injection rates, and different fracture-matrix interaction (by increasing absolute matrix permeability at the fracture matrix boundary) for a larger fracture interaction under transient or balanced-state flow regimes. Two conceptual block models were developed based on different numerical approaches: a two-dimensional discrete-fracture-network model (DFNM) and a one-dimensional dual continuum model (DCM). The DFNM was used as a surrogate for a natural block to produce synthetic breakthrough curves of water and tracer concentration under transient or balanced-state conditions. The DCM is the approach typically used for the Yucca Mountain Project because of its computational efficiency. The AFC was incorporated into the DCM to capture heterogeneous flow patterns that occur in unsaturated fractured rocks. The simulation results from the DCM were compared with the results from the DFNM to determine whether the DCM could predict the water flow and tracer transport observed in the DFNM at the scale of the experiment. It was found that implementing the AFC in the DCM improved the prediction of unsaturated flow and that the flow and transport experiments with low injection rates in the DFNM were compared better with the AFC implemented DCM at the meter scale. However, the estimated AFC parameter varied from 0.38 to 1.0 with different flow conditions, suggesting that the AFC parameter was not a sufficient to fully capture the complexity of the flow processes in a one meter sized discrete fracture network

  8. AN ACTIVE FRACTURE MODEL FOR UNSATURATED FLOW AND TRANSPORT

    International Nuclear Information System (INIS)

    HUI-HAI LIU, GUDMUNDUR S. BODVARSSON AND CHRISTINE DOUGHTY

    1999-01-01

    Fracture/matrix (F/M) interaction is a key factor affecting flow and transport in unsaturated fractured rocks. In classic continuum approaches (Warren and Root, 1963), it is assumed that flow occurs through all the connected fractures and is uniformly distributed over the entire fracture area, which generally gives a relatively large F/M interaction. However, fractures seem to have limited interaction with the surrounding matrix at Yucca Mountain, Nevada, as suggested by geochemical nonequilibrium between the perched water (resulting mainly from fracture flow) and pore water in the rock matrix. Because of the importance of the F/M interaction and related issues, there is a critical need to develop new approaches to accurately consider the interaction reduction inferred from field data at the Yucca Mountain site. Motivated by this consideration, they have developed an active fracture model based on the hypothesis that not all connected fractures actively conduct water in unsaturated fractured rocks

  9. Waste package performance in unsaturated rock

    International Nuclear Information System (INIS)

    Pigford, T.H.; Lee, W.W.-L.

    1989-03-01

    The unsaturated rock and near-atmospheric pressure of the potential nuclear waste repository at Yucca Mountain present new problems of predicting waste package performance. In this paper we present some illustrations of predictions of waste package performance and discuss important data needs. 11 refs., 9 figs., 1 tab

  10. Groundwater recharge dynamics in unsaturated fractured chalk: a case study

    Science.gov (United States)

    Cherubini, Claudia; Pastore, Nicola; Giasi, Concetta I.; Allegretti, Nicolaetta M.

    2016-04-01

    The heterogeneity of the unsaturated zone controls its hydraulic response to rainfall and the extent to which pollutants are delayed or attenuated before reaching groundwater. It plays therefore a very important role in the recharge of aquifers and the transfer of pollutants because of the presence of temporary storage zones and preferential flows. A better knowledge of the physical processes in the unsaturated zone would allow an improved assessment of the natural recharge in a heterogeneous aquifer and of its vulnerability to surface-applied pollution. The case study regards the role of the thick unsaturated zone of the Cretaceous chalk aquifer in Picardy (North of France) that controls the hydraulic response to rainfall. In the North Paris Basin, much of the recharge must pass through a regional chalk bed that is composed of a porous matrix with embedded fractures. Different types of conceptual models have been formulated to explain infiltration and recharge processes in the unsaturated fractured rock. The present study analyses the episodic recharge in fractured Chalk aquifer using the kinematic diffusion theory to predict water table fluctuation in response to rainfall. From an analysis of the data, there is the evidence of 1) a seasonal behavior characterized by a constant increase in the water level during the winter/spring period and a recession period, 2) a series of episodic behaviors during the summer/autumn. Kinematic diffusion models are useful for predict preferential fluxes and dynamic conditions. The presented approach conceptualizes the unsaturated flow as a combination of 1) diffusive flow refers to the idealized portion of the pore space of the medium within the flow rate is driven essentially by local gradient of potential; 2) preferential flow by which water moves across macroscopic distances through conduits of macropore length.

  11. Flow and contaminant transport in fractured rocks

    International Nuclear Information System (INIS)

    Bear, J.; Tsang, C.F.; Marsily, G. de

    1993-01-01

    This book is a compilation of nine articles dealing with various aspect of flow in fractured media. Articles range from radionuclide waste to multiphase flow in petroleum reservoirs to practical field test methods. Each chapter contains copious figures to aid the reader, but is also a detailed in-depth analysis of some major flow problem. The subjects covered are as follows: an introduction to flow and transport models; solute transport in fractured rock with application to radioactive waste repositories; solute transport models through fractured networks; theoretical view of stochastic models of fracture systems; numerical models of tracers; multiphase flow models in fractured systems and petroleum reservoirs; unsaturated flow modeling; comparative analysis of various flow modeling techniques in fractured media; and, a summary of field methods for measuring transfers of mass, heat, contaminant, momentum, and electrical charge in fractured media

  12. The Unsaturated Hydromechanical Coupling Model of Rock Slope Considering Rainfall Infiltration Using DDA

    Directory of Open Access Journals (Sweden)

    Xianshan Liu

    2017-01-01

    Full Text Available Water flow and hydromechanical coupling process in fractured rocks is more different from that in general porous media because of heterogeneous spatial fractures and possible fracture-dominated flow; a saturated-unsaturated hydromechanical coupling model using a discontinuous deformation analysis (DDA similar to FEM and DEM was employed to analyze water movement in saturated-unsaturated deformed rocks, in which the Van-Genuchten model differently treated the rock and fractures permeable properties to describe the constitutive relationships. The calibrating results for the dam foundation indicated the validation and feasibility of the proposed model and are also in good agreement with the calculations based on DEM still demonstrating its superiority. And then, the rainfall infiltration in a reservoir rock slope was detailedly investigated to describe the water pressure on the fault surface and inside the rocks, displacement, and stress distribution under hydromechanical coupling conditions and uncoupling conditions. It was observed that greater rainfall intensity and longer rainfall time resulted in lower stability of the rock slope, and larger difference was very obvious between the hydromechanical coupling condition and uncoupling condition, demonstrating that rainfall intensity, rainfall time, and hydromechanical coupling effect had great influence on the saturated-unsaturated water flow behavior and mechanical response of the fractured rock slopes.

  13. Thermal conductivity of unsaturated clay-rocks

    Directory of Open Access Journals (Sweden)

    D. Jougnot

    2010-01-01

    Full Text Available The parameters used to describe the electrical conductivity of a porous material can be used to describe also its thermal conductivity. A new relationship is developed to connect the thermal conductivity of an unsaturated porous material to the thermal conductivity of the different phases of the composite, and two electrical parameters called the first and second Archie's exponents. A good agreement is obtained between the new model and thermal conductivity measurements performed using packs of glass beads and core samples of the Callovo-Oxfordian clay-rocks at different saturations of the water phase. We showed that the three model parameters optimised to fit the new model against experimental data (namely the thermal conductivity of the solid phase and the two Archie's exponents are consistent with independent estimates. We also observed that the anisotropy of the effective thermal conductivity of the Callovo-Oxfordian clay-rock was mainly due to the anisotropy of the thermal conductivity of the solid phase.

  14. Water infiltration into exposed fractured rock surfaces

    International Nuclear Information System (INIS)

    Rasmussen, T.C.; Evans, D.D.

    1993-01-01

    Fractured rock media are present at many existing and potential waste disposal sites, yet characterization data and physical relationships are not well developed for such media. This study focused on water infiltration characteristics of an exposed fractured rock as an approach for defining the upper boundary condition for unsaturated-zone water percolation and contaminant transport modeling. Two adjacent watersheds of 0.24 and 1.73 ha with slopes up to 45% were instrumented for measuring rainfall and runoff. Fracture density was measured from readily observable fracture traces on the surface. Three methods were employed to evaluate the rainfall-runoff relationship. The first method used the annual totals and indicated that only 22.5% of rainfall occurred as runoff for the 1990-1991 water year, which demonstrates a high water intake rate by the exposed fracture system. The second method employed total rainfall and runoff for individual storms in conjunction with the commonly used USDA Soil Conservation Service curve number method developed for wide ranges of soils and vegetation. Curve numbers between 75 and 85 were observed for summer and winter storms with dry antecedent runoff conditions, while values exceeded 90 for wet conditions. The third method used a mass-balance approach for four major storms, which indicated that water intake rates ranged from 2.0 to 7.3 mm h -1 , yielding fracture intake velocities ranging from 122 to 293 m h -1 . The three analyses show the complexity of the infiltration process for fractured rock. However, they contribute to a better understanding of the upper boundary condition for predicting contaminant transport through an unsaturated fractured rock medium. 17 refs., 4 figs., 1 tab

  15. Hydraulic fracturing of rock-fill dam

    Directory of Open Access Journals (Sweden)

    Jun-Jie WANG

    2016-02-01

    Full Text Available The condition in which hydraulic fracturing in core of earth-rock fill dam maybe induced, the mechanism by which the reason of hydraulic fracturing canbe explained, and the failure criterion by which the occurrence of hydraulicfracturing can be determined, were investigated. The condition dependson material properties such as, cracks in the core and low permeability ofcore soil, and “water wedging” action in cracks. An unsaturated core soiland fast impounding are the prerequisites for the formation of “waterwedging” action. The mechanism of hydraulic fracturing can be explainedby fracture mechanics. The crack propagation induced by water pressuremay follow any of mode I, mode II and mixed mode I-II. Based on testingresults of a core soil, a new criterion for hydraulic fracturing was suggested,from which mechanisms of hydraulic fracturing in the core of rock-fill damwere discussed. The results indicated that factors such as angle betweencrack surface and direction of principal stress, local stress state at thecrack, and fracture toughness KIC of core soil may largely affect theinduction of hydraulic fracturing and the mode of the propagation of thecrack.The condition in which hydraulic fracturing in core of earth-rock fill dam maybe induced, the mechanism by which the reason of hydraulic fracturing canbe explained, and the failure criterion by which the occurrence of hydraulicfracturing can be determined, were investigated. The condition dependson material properties such as, cracks in the core and low permeability ofcore soil, and “water wedging” action in cracks. An unsaturated core soiland fast impounding are the prerequisites for the formation of “waterwedging” action. The mechanism of hydraulic fracturing can be explainedby fracture mechanics. The crack propagation induced by water pressuremay follow any of mode I, mode II and mixed mode I-II. Based on testingresults of a core soil, a new criterion for hydraulic fracturing

  16. Fracture characteristics in Japanese rock

    International Nuclear Information System (INIS)

    Ijiri, Yuji; Sawada, Atsushi; Akahori, Kuniaki

    1999-11-01

    It is crucial for the performance assessment of geosphere to evaluate the characteristics of fractures that can be dominant radionuclide migration pathways from a repository to biosphere. This report summarizes the characteristics of fractures obtained from broad literature surveys and the fields surveys at the Kamaishi mine in northern Japan and at outcrops and galleries throughout the country. The characteristics of fractures described in this report are fracture orientation, fracture shape, fracture frequency, fracture distribution in space, transmissivity of fracture, fracture aperture, fracture fillings, alteration halo along fracture, flow-wetted surface area in fracture, and the correlation among these characteristics. Since granitic rock is considered the archetype fractured media, a large amount of fracture data is available in literature. In addition, granitic rock has been treated as a potential host rock in many overseas programs, and has JNC performed a number of field observations and experiments in granodiorite at the Kamaishi mine. Therefore, the characteristics of fractures in granitic rock are qualitatively and quantitatively clarified to some extent in this report, while the characteristics of fractures in another rock types are not clarified. (author)

  17. Quantifying Preferential Flow and Seasonal Storage in an Unsaturated Fracture-Facial Domain

    Science.gov (United States)

    Nimmo, J. R.; Malek-Mohammadi, S.

    2012-12-01

    Preferential flow through deep unsaturated zones of fractured rock is hydrologically important to a variety of contaminant transport and water-resource issues. The unsaturated zone of the English Chalk Aquifer provides an important opportunity for a case study of unsaturated preferential flow in isolation from other flow modes. The chalk matrix has low hydraulic conductivity and stays saturated, owing to its fine uniform pores and the wet climate of the region. Therefore the substantial fluxes observed in the unsaturated chalk must be within fractures and interact minimally with matrix material. Price et al. [2000] showed that irregularities on fracture surfaces provide a significant storage capacity in the chalk unsaturated zone, likely accounting for volumes of water required to explain unexpected dry-season water-table stability during substantial continuing streamflow observed by Lewis et al. [1993] In this presentation we discuss and quantify the dynamics of replenishment and drainage of this unsaturated zone fracture-face storage domain using a modification of the source-responsive model of Nimmo [2010]. This model explains the processes in terms of two interacting flow regimes: a film or rivulet preferential flow regime on rough fracture faces, active on an individual-storm timescale, and a regime of adsorptive and surface-tension influences, resembling traditional diffuse formulations of unsaturated flow, effective mainly on a seasonal timescale. The modified model identifies hydraulic parameters for an unsaturated fracture-facial domain lining the fractures. Besides helping to quantify the unsaturated zone storage described by Price et al., these results highlight the importance of research on the topic of unsaturated-flow relations within a near-fracture-surface domain. This model can also facilitate understanding of mechanisms for reinitiation of preferential flow after temporary cessation, which is important in multi-year preferential flow through deep

  18. Relative Permeability of Fractured Rock

    Energy Technology Data Exchange (ETDEWEB)

    Mark D. Habana

    2002-06-30

    Contemporary understanding of multiphase flow through fractures is limited. Different studies using synthetic fractures and various fluids have yielded different relative permeability-saturation relations. This study aimed to extend the understanding of multiphase flow by conducting nitrogen-water relative permeability experiments on a naturally-fractured rock from The Geysers geothermal field. The steady-state approach was used. However, steady state was achieved only at the endpoint saturations. Several difficulties were encountered that are attributed to phase interference and changes in fracture aperture and surface roughness, along with fracture propagation/initiation. Absolute permeabilities were determined using nitrogen and water. The permeability values obtained change with the number of load cycles. Determining the absolute permeability of a core is especially important in a fractured rock. The rock may change as asperities are destroyed and fractures propagate or st rain harden as the net stresses vary. Pressure spikes occurred in water a solute permeability experiments. Conceptual models of an elastic fracture network can explain the pressure spike behavior. At the endpoint saturations the water relative permeabilities obtained are much less than the nitrogen gas relative permeabilities. Saturations were determined by weighing and by resistivity calculations. The resistivity-saturation relationship developed for the core gave saturation values that differ by 5% from the value determined by weighing. Further work is required to complete the relative permeability curve. The steady-state experimental approach encountered difficulties due to phase interference and fracture change. Steady state may not be reached until an impractical length of time. Thus, unsteady-state methods should be pursued. In unsteady-state experiments the challenge will be in quantifying rock fracture change in addition to fluid flow changes.

  19. Sealing of rock fractures

    International Nuclear Information System (INIS)

    Pusch, R.; Erlstroem, M.; Boergesson, L.

    1985-12-01

    The major water-bearing fractures in granite usually from fairly regular sets but the extension and degree of connectivity is varying. This means that only a few fractures that are interconnected with the deposition holes and larger water-bearing structures in a HLW repository are expected and if they can be identified and cut off through sealing it would be possible to improve the isolation of waste packages very effectively. Nature's own fracture sealing mechanisms may be simulated and a survey of the involved processes actually suggests a number of possible filling methods and substances. Most of them require high temperature and pressure and correspondingly sophisticated techniques, but some are of potential interest for immediate application with rather moderate effort. Such a technique is to fill the fractures with clayey substances which stay flexible and low-permeable provided that they remain physically and chemically intact. It is demonstrated in the report that effective grouting requires a very low viscosity and shear strength of the substance and this can be achieved by mechanical agitation as demonstrated in this report. Thus, by superimposing static pressure and shear waves induced by percussion hammering at a suitable frequency, clays and fine-grained silts as well as cement can be driven into fractures with an average aperture as small as 0.1 mm. Experiments were made in the laboratory using concrete and steel plates, and a field pilot test was also conducted under realistic conditions on site in Stripa. They all demonstrated the practicality of the 'dynamic injection technique' and that the fluid condition of the grouts yielded complete filling of the injected space to a considerable distance from the injection point. The field test indicated a good sealing ability as well as a surprisingly high resistance to erosion and piping. (author)

  20. Deformations of fractured rock

    International Nuclear Information System (INIS)

    Stephansson, O.

    1977-09-01

    Results of the DBM and FEM analysis in this study indicate that a suitable rock mass for repository of radioactive waste should be moderately jointed (about 1 joint/m 2 ) and surrounded by shear zones of the first order. This allowes for a gentle and flexible deformation under tectonic stresses and prevent the development of large cross-cutting failures in the repository area. (author)

  1. Tracer transport in fractured rocks

    International Nuclear Information System (INIS)

    Tsang, C.F.; Tsang, Y.W.; Hale, F.V.

    1988-07-01

    Recent interest in the safety of toxic waste underground disposal and nuclear waste geologic repositories has motivated many studies of tracer transport in fractured media. Fractures occur in most geologic formations and introduce a high degree of heterogeneity. Within each fracture, the aperture is not constant in value but strongly varying. Thus for such media, tracer tends to flow through preferred flowpaths or channels within the fractures. Along each of these channels, the aperture is also strongly varying. A detailed analysis is carried out on a 2D single fracture with variable apertures and the flow through channels is demonstrated. The channels defined this way are not rigidly set pathways for tracer transport, but are the preferred flow paths in the sense of stream-tubes in the potential theory. It is shown that such variable-aperture channels can be characterized by an aperture probability distribution function, and not by the exact deterministic geometric locations. We also demonstrate that the 2D tracer transport in a fracture can be calculated by a model of a system of 1D channels characterized by this distribution function only. Due to the channeling character of tracer transport in fractured rock, random point measurements of tracer breakthrough curves may give results with a wide spread in value due to statistical fluctuations. The present paper suggests that such a wide spread can probably be greatly reduced by making line/areal (or multiple) measurements covering a few spatial correlation lengths. 13 refs., 11 figs., 1 tab

  2. Nonlinear dynamics in flow through unsaturated fractured-porous media: Status and perspectives

    Energy Technology Data Exchange (ETDEWEB)

    Faybishenko, Boris

    2002-11-27

    The need has long been recognized to improve predictions of flow and transport in partially saturated heterogeneous soils and fractured rock of the vadose zone for many practical applications, such as remediation of contaminated sites, nuclear waste disposal in geological formations, and climate predictions. Until recently, flow and transport processes in heterogeneous subsurface media with oscillating irregularities were assumed to be random and were not analyzed using methods of nonlinear dynamics. The goals of this paper are to review the theoretical concepts, present the results, and provide perspectives on investigations of flow and transport in unsaturated heterogeneous soils and fractured rock, using the methods of nonlinear dynamics and deterministic chaos. The results of laboratory and field investigations indicate that the nonlinear dynamics of flow and transport processes in unsaturated soils and fractured rocks arise from the dynamic feedback and competition between various nonlinear physical processes along with complex geometry of flow paths. Although direct measurements of variables characterizing the individual flow processes are not technically feasible, their cumulative effect can be characterized by analyzing time series data using the models and methods of nonlinear dynamics and chaos. Identifying flow through soil or rock as a nonlinear dynamical system is important for developing appropriate short- and long-time predictive models, evaluating prediction uncertainty, assessing the spatial distribution of flow characteristics from time series data, and improving chemical transport simulations. Inferring the nature of flow processes through the methods of nonlinear dynamics could become widely used in different areas of the earth sciences.

  3. Nonlinear dynamics in flow through unsaturated fractured porous media: Status and perspectives

    International Nuclear Information System (INIS)

    Faybishenko, Boris

    2002-01-01

    The need has long been recognized to improve predictions of flow and transport in partially saturated heterogeneous soils and fractured rock of the vadose zone for many practical applications, such as remediation of contaminated sites, nuclear waste disposal in geological formations, and climate predictions. Until recently, flow and transport processes in heterogeneous subsurface media with oscillating irregularities were assumed to be random and were not analyzed using methods of nonlinear dynamics. The goals of this paper are to review the theoretical concepts, present the results, and provide perspectives on investigations of flow and transport in unsaturated heterogeneous soils and fractured rock, using the methods of nonlinear dynamics and deterministic chaos. The results of laboratory and field investigations indicate that the nonlinear dynamics of flow and transport processes in unsaturated soils and fractured rocks arise from the dynamic feedback and competition between various nonlinear physical processes along with complex geometry of flow paths. Although direct measurements of variables characterizing the individual flow processes are not technically feasible, their cumulative effect can be characterized by analyzing time series data using the models and methods of nonlinear dynamics and chaos. Identifying flow through soil or rock as a nonlinear dynamical system is important for developing appropriate short- and long-time predictive models, evaluating prediction uncertainty, assessing the spatial distribution of flow characteristics from time series data, and improving chemical transport simulations. Inferring the nature of flow processes through the methods of nonlinear dynamics could become widely used in different areas of the earth sciences

  4. Hydraulic conductivity of rock fractures

    International Nuclear Information System (INIS)

    Zimmerman, R.W.; Bodvarsson, G.S.

    1994-10-01

    Yucca Mountain, Nevada contains numerous geological units that are highly fractured. A clear understanding of the hydraulic conductivity of fractures has been identified as an important scientific problem that must be addressed during the site characterization process. The problem of the flow of a single-phase fluid through a rough-walled rock fracture is discussed within the context of rigorous fluid mechanics. The derivation of the cubic law is given as the solution to the Navier-Stokes equations for flow between smooth, parallel plates, the only fracture geometry that is amenable to exact treatment. The various geometric and kinetic conditions that are necessary in order for the Navier-Stokes equations to be replaced by the more tractable lubrication or Hele-Shaw equations are studied and quantified. Various analytical and numerical results are reviewed pertaining to the problem of relating the effective hydraulic aperture to the statistics of the aperture distribution. These studies all lead to the conclusion that the effective hydraulic aperture is always less than the mean aperture, by a factor that depends on the ratio of the mean value of the aperture to its standard deviation. The tortuosity effect caused by regions where the rock walls are in contact with each other is studied using the Hele-Shaw equations, leading to a simple correction factor that depends on the area fraction occupied by the contact regions. Finally, the predicted hydraulic apertures are compared to measured values for eight data sets from the literature for which aperture and conductivity data were available on the same fracture. It is found that reasonably accurate predictions of hydraulic conductivity can be made based solely on the first two moments of the aperture distribution function, and the proportion of contact area. 68 refs

  5. Channelling of flow through fractures in rock

    International Nuclear Information System (INIS)

    Bourke, P.J.

    1987-05-01

    A method of mapping the channelling of flow in rock fractures formed by contacts between rock faces and of measuring the effective apertures of channels has been developed. Some typical results are given. (author)

  6. Transport of gaseous C-14 from a repository in unsaturated rock

    International Nuclear Information System (INIS)

    Light, W.B.; Chambre, P.L.; Lee, W. L.; Pigford, T.H.; California Univ., Berkeley, CA

    1990-09-01

    The authors predict the transport of gaseous 14 CO 2 from a nuclear waste repository in unsaturated rock using a porous-medium model. This model is justified if the appropriate modified Peclet number, which indicates equilibrium between gas in fractures and liquid in rock pores, is much less than unity. Numerical illustrations are given which are applicable to the proposed repository at Yucca Mountain which is 350 m underground. Maximum predicted concentrations of 14 CO 2 near the ground surface are comparable to the USNRC limit for unrestricted areas. Maximum predicted dose rates above ground are less than 1% of background. Travel times are predicted to be hundreds to thousands of years. For some cases, it is shown that the release rate from the source has negligible effect on concentrations at the ground surface. 15 refs., 10 figs., 1 tab

  7. Rock fracture processes in chemically reactive environments

    Science.gov (United States)

    Eichhubl, P.

    2015-12-01

    Rock fracture is traditionally viewed as a brittle process involving damage nucleation and growth in a zone ahead of a larger fracture, resulting in fracture propagation once a threshold loading stress is exceeded. It is now increasingly recognized that coupled chemical-mechanical processes influence fracture growth in wide range of subsurface conditions that include igneous, metamorphic, and geothermal systems, and diagenetically reactive sedimentary systems with possible applications to hydrocarbon extraction and CO2 sequestration. Fracture processes aided or driven by chemical change can affect the onset of fracture, fracture shape and branching characteristics, and fracture network geometry, thus influencing mechanical strength and flow properties of rock systems. We are investigating two fundamental modes of chemical-mechanical interactions associated with fracture growth: 1. Fracture propagation may be aided by chemical dissolution or hydration reactions at the fracture tip allowing fracture propagation under subcritical stress loading conditions. We are evaluating effects of environmental conditions on critical (fracture toughness KIc) and subcritical (subcritical index) fracture properties using double torsion fracture mechanics tests on shale and sandstone. Depending on rock composition, the presence of reactive aqueous fluids can increase or decrease KIc and/or subcritical index. 2. Fracture may be concurrent with distributed dissolution-precipitation reactions in the hostrock beyond the immediate vicinity of the fracture tip. Reconstructing the fracture opening history recorded in crack-seal fracture cement of deeply buried sandstone we find that fracture length growth and fracture opening can be decoupled, with a phase of initial length growth followed by a phase of dominant fracture opening. This suggests that mechanical crack-tip failure processes, possibly aided by chemical crack-tip weakening, and distributed solution-precipitation creep in the

  8. Dissipative particle dynamics simulation of fluid motion through an unsaturated fracture and fracture junction

    International Nuclear Information System (INIS)

    Liu Moubin; Meakin, Paul; Huang Hai

    2007-01-01

    Multiphase fluid motion in unsaturated fractures and fracture networks involves complicated fluid dynamics, which is difficult to model using grid-based continuum methods. In this paper, the application of dissipative particle dynamics (DPD), a relatively new mesoscale method to simulate fluid motion in unsaturated fractures is described. Unlike the conventional DPD method that employs a purely repulsive conservative (non-dissipative) particle-particle interaction to simulate the behavior of gases, we used conservative particle-particle interactions that combine short-range repulsive and long-range attractive interactions. This new conservative particle-particle interaction allows the behavior of multiphase systems consisting of gases, liquids and solids to be simulated. Our simulation results demonstrate that, for a fracture with flat parallel walls, the DPD method with the new interaction potential function is able to reproduce the hydrodynamic behavior of fully saturated flow, and various unsaturated flow modes including thin film flow, wetting and non-wetting flow. During simulations of flow through a fracture junction, the fracture junction can be fully or partially saturated depending on the wetting property of the fluid, the injection rate and the geometry of the fracture junction. Flow mode switching from a fully saturated flow to a thin film flow can also be observed in the fracture junction

  9. A mountain-scale model for characterizing unsaturated flow and transport in fractured tuffs of Yucca Mountain

    International Nuclear Information System (INIS)

    Wu, Yu-Shu; Lu, Guoping; Zhang, Keni; Bodvarsson, G.S.

    2003-01-01

    This paper presents a large-scale modeling study characterizing fluid flow and tracer transport in the unsaturated zone of Yucca Mountain, Nevada, the proposed underground repository site for storing high-level radioactive waste. The modeling study is conducted using a three-dimensional numerical model, which incorporates a wide variety of field data and takes into account the coupled processes of flow and transport in Yucca Mountain's highly heterogeneous, unsaturated, fractured porous rock. The modeling approach is based on a dual-continuum formulation. Using different conceptual models of unsaturated flow, various scenarios of current and future climate conditions and their effects on the unsaturated zone are evaluated to aid in the assessment of the repository's system performance. These models are calibrated against field-measured data. Model-predicted flow and transport processes under current and future climates are discussed

  10. Deep fracturation of granitic rock mass

    International Nuclear Information System (INIS)

    Bles, J.L.; Blanchin, R.; Bonijoly, D.; Dutartre, P.; Feybesse, J.L.; Gros, Y.; Landry, J.; Martin, P.

    1986-01-01

    This documentary study realized with the financial support of the European Communities and the CEA aims at the utilization of available data for the understanding of the evolution of natural fractures in granitic rocks from the surface to deep underground, in various feasibility studies dealing with radioactive wastes disposal. The Mont Blanc road tunnel, the EDF Arc-Isere gallerie, the Auriat deep borehole and the Pyrenean rock mass of Bassies are studied. In this study are more particularly analyzed the relationship between small fractures and large faults, evolution with depth of fracture density and direction, consequences of rock decompression and relationship between fracturation and groundwater [fr

  11. The movement of groundwater flow in unsaturated fractured porous medium

    International Nuclear Information System (INIS)

    Li Jinxuan

    1995-01-01

    The author analyses the fundamental processes governing infiltration in fractured porous rock. Asymptotic solutions for the front movement are given for each flow period and comparisons with numerical solutions are made. The result of the study is relevant to nuclear waste storage, hazardous waste disposal and petroleum recovery

  12. Penetration of liquid fingers into superheated fractured rock

    Science.gov (United States)

    Birkholzer, Jens

    2003-04-01

    Water infiltrating down a fracture in unsaturated rock experiences complex fluid flow and heat transfer phenomena when entering above-boiling rock temperature regions. Such conditions are expected, for example, after emplacement of heat-generating nuclear waste in underground repositories. A new efficient semianalytical method is proposed in this paper that simulates the flow processes of infiltration events subject to vigorous boiling from the adjacent hot rock. It is assumed that liquid flow forms in localized preferential flow paths and that infiltration events are typically short in duration but large in magnitude relative to the average net infiltration. The new solution scheme is applied to several test cases studying sensitivity to a variety of input parameters. Sample simulations are performed for conditions representative of the potential nuclear waste repository at Yucca Mountain, Nevada. A characteristic parameter is introduced that provides a quick estimate of the relative significance of boiling at a given location of interest.

  13. Penetration of liquid fingers into superheated fractured rock

    International Nuclear Information System (INIS)

    Birkholzer, Jens

    2002-01-01

    Water infiltrating down a fracture in unsaturated rock experiences complex fluid-flow and heat-transfer phenomena when entering above-boiling rock temperature regions. Such conditions are expected, for example, after emplacement of heat-generating nuclear waste in underground repositories. A new, efficient semi-analytical method is proposed in this paper that simulates the flow processes of infiltration events subject to vigorous boiling from the adjacent hot rock. It is assumed that liquid flow forms in localized preferential flow paths, and that infiltration events are typically short in duration but large in magnitude relative to the average net infiltration. The new solution scheme is applied to several test cases studying sensitivity to a variety of input parameters. Sample simulations are performed for conditions representative of the potential nuclear waste repository at Yucca Mountain, Nevada. A characteristic parameter is introduced that provides a quick estimate of the relative significance of boiling at a given location of interest

  14. Cleavage and creep fracture of rock salt

    International Nuclear Information System (INIS)

    Chan, K.S.; Munson, D.E.; Bodner, S.R.

    1996-01-01

    The dominant failure mechanism in rock salt at ambient temperature is either cleavage or creep fracture. Since the transition of creep fracture to cleavage in a compressive stress field is not well understood, failure of rock salt by cleavage and creep fracture is analyzed in this paper to elucidate the effect of stress state on the competition between these two fracture mechanisms. For cleavage fracture, a shear crack is assumed to cause the formation and growth of a symmetric pair of wing cracks in a predominantly compressive stress field. The conditions for wing-crack instability are derived and presented as the cleavage fracture boundary in the fracture mechanism map. Using an existing creep fracture model, stress conditions for the onset of creep fracture and isochronous failure curves of specified times-to-rupture are calculated and incorporated into the fracture mechanism map. The regimes of dominance by cleavage and creep fracture are established and compared with experimental data. The result indicates that unstable propagation of cleavage cracks occurs only in the presence of tensile stress. The onset of creep fracture is promoted by a tensile stress, but can be totally suppressed by a high confining pressure. Transition of creep fracture to cleavage occurs when critical conditions of stress difference and tensile stress for crack instability are exceeded

  15. Elastic Rock Heterogeneity Controls Brittle Rock Failure during Hydraulic Fracturing

    Science.gov (United States)

    Langenbruch, C.; Shapiro, S. A.

    2014-12-01

    For interpretation and inversion of microseismic data it is important to understand, which properties of the reservoir rock control the occurrence probability of brittle rock failure and associated seismicity during hydraulic stimulation. This is especially important, when inverting for key properties like permeability and fracture conductivity. Although it became accepted that seismic events are triggered by fluid flow and the resulting perturbation of the stress field in the reservoir rock, the magnitude of stress perturbations, capable of triggering failure in rocks, can be highly variable. The controlling physical mechanism of this variability is still under discussion. We compare the occurrence of microseismic events at the Cotton Valley gas field to elastic rock heterogeneity, obtained from measurements along the treatment wells. The heterogeneity is characterized by scale invariant fluctuations of elastic properties. We observe that the elastic heterogeneity of the rock formation controls the occurrence of brittle failure. In particular, we find that the density of events is increasing with the Brittleness Index (BI) of the rock, which is defined as a combination of Young's modulus and Poisson's ratio. We evaluate the physical meaning of the BI. By applying geomechanical investigations we characterize the influence of fluctuating elastic properties in rocks on the probability of brittle rock failure. Our analysis is based on the computation of stress fluctuations caused by elastic heterogeneity of rocks. We find that elastic rock heterogeneity causes stress fluctuations of significant magnitude. Moreover, the stress changes necessary to open and reactivate fractures in rocks are strongly related to fluctuations of elastic moduli. Our analysis gives a physical explanation to the observed relation between elastic heterogeneity of the rock formation and the occurrence of brittle failure during hydraulic reservoir stimulations. A crucial factor for understanding

  16. Physical processes that control droplet transport in rock fracture systems

    Science.gov (United States)

    Hay, Katrina Moran

    Aquifer recharge is generally driven by fluids that move from the Earths surface to groundwater through the unsaturated zone, also known as the vadose zone. When the vadose zone is fractured, fluids, which may include contaminants, can move through the fracture network as well as the porous matrix. Such a network of fractures can provide a more rapid path, thereby reducing contact time between the fluid and the matrix. Contact time allows for exchange of solutes between the fluid and the porous matrix, thus being able to quantify contact time is important. In addition, the behavior of fluids within a fracture network has been found to be very complex; large-scale models are yet not able to predict transport paths or flux rates. Because, small-scale flow phenomena can strongly influence the large-scale behavior of fluid movement through systems of fractures, it is important that small-scale dynamics be properly understood in order to improve our predictive capabilities in these complex systems. Relevant flow dynamics includes the impact of boundary conditions, fluid modes that evolve in time and space and transitions between modes. This thesis presents three investigations aimed at understanding the physical processes governing fluid movement in unsaturated fractures, with the ultimate goal of improving predictive relationships for fluid transport in rock fracture systems. These investigations include a theoretical analysis of the wetting of a rough surface, an experimental study of the dynamics of fluid droplets (or liquid bridges) moving in a single fracture and a theoretical analysis of the movement of a fluid droplet encountering a fracture intersection. Each investigation is motivated by environmental applications. Development of an analytical equation for the wetting of a rough surface is based on a balance between capillary forces and frictional resistive forces. The resulting equation predicts movement of the liquid invasion front driven solely by the

  17. A performance assessment methodology for high-level radioactive waste disposal in unsaturated, fractured tuff

    International Nuclear Information System (INIS)

    Gallegos, D.P.

    1991-07-01

    Sandia National Laboratories, has developed a methodology for performance assessment of deep geologic disposal of high-level nuclear waste. The applicability of this performance assessment methodology has been demonstrated for disposal in bedded salt and basalt; it has since been modified for assessment of repositories in unsaturated, fractured tuff. Changes to the methodology are primarily in the form of new or modified ground water flow and radionuclide transport codes. A new computer code, DCM3D, has been developed to model three-dimensional ground-water flow in unsaturated, fractured rock using a dual-continuum approach. The NEFTRAN 2 code has been developed to efficiently model radionuclide transport in time-dependent velocity fields, has the ability to use externally calculated pore velocities and saturations, and includes the effect of saturation dependent retardation factors. In order to use these codes together in performance-assessment-type analyses, code-coupler programs were developed to translate DCM3D output into NEFTRAN 2 input. Other portions of the performance assessment methodology were evaluated as part of modifying the methodology for tuff. The scenario methodology developed under the bedded salt program has been applied to tuff. An investigation of the applicability of uncertainty and sensitivity analysis techniques to non-linear models indicate that Monte Carlo simulation remains the most robust technique for these analyses. No changes have been recommended for the dose and health effects models, nor the biosphere transport models. 52 refs., 1 fig

  18. Mechanical dispersion in fractured crystalline rock systems

    International Nuclear Information System (INIS)

    Lafleur, D.W.; Raven, K.G.

    1986-12-01

    This report compiles and evaluates the hydrogeologic parameters describing the flow of groundwater and transport of solutes in fractured crystalline rocks. This report describes the processes of mechanical dispersion in fractured crystalline rocks, and compiles and evaluates the dispersion parameters determined from both laboratory and field tracer experiments. The compiled data show that extrapolation of the reliable test results performed over intermediate scales (10's of m and 10's to 100's of hours) to larger spatial and temporal scales required for performance assessment of a nuclear waste repository in crystalline rock is not justified. The reliable measures of longitudinal dispersivity of fractured crystalline rock are found to range between 0.4 and 7.8 m

  19. SEEPAGE INTO DRIFTS IN UNSATRUATED FRACTURED ROCK AT YUCCA MOUNTAIN

    International Nuclear Information System (INIS)

    JENS BIRHOLZER; GUOMIN LI; CHIN-FU TSANG; YVONNE TSANG

    1998-01-01

    An important issue for the long-term performance of underground nuclear waste repositories is the rate of seepage into the waste emplacement drifts. A prediction of the future seepage rate is particularly complicated for the potential repository site at Yucca Mountain, Nevada, as it is located in thick, partially saturated, fractured tuff formations. The long-term situation in the drifts several thousand years after waste emplacement will be characterized by a relative humidity level close to or equal to 100%. as the drifts will be sealed and unventilated, and the waste packages will have cooled. The underground tunnels will then act as capillary barriers for the unsaturated flow, ideally diverting water around them, if the capillary forces are stronger than gravity and viscous forces. Seepage into the drifts will only be possible if the hydraulic pressure in the rock close to the drift walls increases to positive values; i.e., the flow field becomes locally saturated. In the present work, we have developed and applied a methodology to study the potential rate of seepage into underground cavities embedded in a variably saturated, heterogeneous fractured rock formation. The fractured rock mass is represented as a stochastic continuum where the fracture permeabilities vary by several orders of magnitude. Three different realizations of random fracture permeability fields are generated, with the random permeability structure based on extensive fracture mapping, borehole video analysis, and in-situ air permeability testing. A 3-D numerical model is used to simulate the heterogeneous steady-state flow field around the drift, with the drift geometry explicitly represented within the numerical discretization grid. A variety of flow scenarios are considered assuming present-day and future climate conditions at Yucca Mountain. The numerical study is complemented by theoretical evaluations of the drift seepage problem, using stochastic perturbation theory to develop a better

  20. Example of fracture characterization in granitic rock

    International Nuclear Information System (INIS)

    Thorpe, R.K.

    1981-03-01

    A detailed study of geologic discontinuities for an underground heater test in highly fractured granitic rock is reported. Several prominent shear fractures were delineated within a 6 x 30 x 15 m rock mass by correlating surface mapping and borehole fracture logs. Oblique-reverse faulting is suspected on at least one of the surfaces, and its inferred borehole intercepts appear to be collinear in the direction of slickensiding observed in the field. Four distinct joint sets were identified, one of which coincides with the shear fractures. Another lies nearly horizontal, and two others are steeply inclined and orthogonal. Fracture lengths and spacings for the four joint sets are represented by lognormal probability distributions

  1. Radionuclide migration in crystalline rock fractures

    International Nuclear Information System (INIS)

    Hoelttae, P.

    2002-01-01

    Crystalline rock has been considered as a host medium for the repository of high radioactive spent nuclear fuel in Finland. The geosphere will act as an ultimate barrier retarding the migration of radionuclides to the biosphere if they are released through the technical barriers. Radionuclide transport is assumed to take place along watercarrying fractures, and retardation will occur both in the fracture and within the rock matrix. To be able to predict the transport and retardation of radionuclides in rock fractures and rock matrices, it is essential to understand the different phenomena involved. Matrix diffusion has been indicated to be an important mechanism, which will retard the transport of radionuclides in rock fractures. Both dispersion and matrix diffusion are processes, which can have similar influences on solute breakthrough curves in fractured crystalline rock. In this work, the migration of radionuclides in crystalline rock fractures was studied by means of laboratory scale column methods. The purpose of the research was to gain a better understanding of various phenomena - particularly matrix diffusion - affecting the transport and retardation behaviour of radionuclides in fracture flow. Interaction between radionuclides and the rock matrix was measured in order to test the compatibility of experimental retardation parameters and transport models used in assessing the safety of underground repositories for spent nuclear fuel. Rock samples of mica gneiss and of unaltered, moderately altered and strongly altered tonalite represented different rock features and porosities offering the possibility to determine experimental boundary limit values for parameters describing both the transport and retardation of radionuclides and rock matrix properties. The dominant matrix diffusion behaviour was demonstrated in porous ceramic column and gas diffusion experiments. Demonstration of the effects of matrix diffusion in crystalline rock fracture succeeded for the

  2. Water flow characteristics of rock fractures

    International Nuclear Information System (INIS)

    Joensson, Lennart

    1990-03-01

    This report has been worked out within the project 'Groundwater flow and dispersion processes in fractured rock' supported by the National Board for Spent Nuclear Fuel (SKN) in Sweden, dnr 96/85. This project is attached to the safety problems involved in the final disposal of spent nuclear fuel. The purpose of the report is to give a survey of the knowledge of fracture characteristics and to discuss this knowledge in relation to the modelling of flow and dispersion of radioactive substances in the fractures

  3. Estimation of Fracture Porosity in an Unsaturated Fractured Welded Tuff Using Gas Tracer Testing

    Energy Technology Data Exchange (ETDEWEB)

    B.M. Freifeild

    2001-10-18

    Kinematic fracture porosity is an important hydrologic transport parameter for predicting the potential of rapid contaminant migration through fractured rock. The transport velocity of a solute moving within a fracture network is inversely related to the fracture porosity. Since fracture porosity is often one or two orders of magnitude smaller than matrix porosity, and fracture permeability is often orders of magnitude greater than matrix permeability, solutes may travel significantly faster in the fracture network than in the surrounding matrix. This dissertation introduces a new methodology for conducting gas tracer tests using a field portable mass spectrometer along with analytical tools for estimating fracture porosity using the measured tracer concentration breakthrough curves. Field experiments were conducted at Yucca Mountain, Nevada, consisting of air-permeability transient testing and gas-tracer-transport tests. The experiments were conducted from boreholes drilled within an underground tunnel as part of an investigation of rock mass hydrological behavior. Air-permeability pressure transients, recorded during constant mass flux injections, have been analyzed using a numerical inversion procedure to identify fracture permeability and porosity. Dipole gas tracer tests have also been conducted from the same boreholes used for air-permeability testing. Mass breakthrough data has been analyzed using a random walk particle-tracking model, with a dispersivity that is a function of the advective velocity. The estimated fracture porosity using the tracer test and air-injection test data ranges from .001 to .015. These values are an order of magnitude greater than the values estimated by others using hydraulically estimated fracture apertures. The estimates of porosity made using air-permeability test data are shown to be highly sensitive to formation heterogeneity. Uncertainty analyses performed on the gas tracer test results show high confidence in the parameter

  4. Estimation of fracture porosity in an unsaturated fractured welded tuff using gas tracer testing

    Energy Technology Data Exchange (ETDEWEB)

    Freifeld, Barry Mark [Univ. of California, Berkeley, CA (United States)

    2001-12-01

    Kinematic fracture porosity is an important hydrologic transport parameter for predicting the potential of rapid contaminant migration through fractured rock. The transport velocity of a solute moving within a fracture network is inversely related to the fracture porosity. Since fracture porosity is often one or two orders of magnitude smaller than matrix porosity, and fracture permeability is often orders of magnitude greater than matrix permeability, solutes may travel significantly faster in the fracture network than in the surrounding matrix. This dissertation introduces a new methodology for conducting gas tracer tests using a field portable mass spectrometer along with analytical tools for estimating fracture porosity using the measured tracer concentration breakthrough curves. Field experiments were conducted at Yucca Mountain, Nevada, consisting of air-permeability transient testing and gas-tracer-transport tests. The experiments were conducted from boreholes drilled within an underground tunnel as part of an investigation of rock mass hydrological behavior. Air-permeability pressure transients, recorded during constant mass flux injections, have been analyzed using a numerical inversion procedure to identify fracture permeability and porosity. Dipole gas tracer tests have also been conducted from the same boreholes used for air-permeability testing. Mass breakthrough data has been analyzed using a random walk particle-tracking model, with a dispersivity that is a function of the advective velocity. The estimated fracture porosity using the tracer test and air-injection test data ranges from .001 to .015. These values are an order of magnitude greater than the values estimated by others using hydraulically estimated fracture apertures. The estimates of porosity made using air-permeability test data are shown to be highly sensitive to formation heterogeneity. Uncertainty analyses performed on the gas tracer test results show high confidence in the parameter

  5. Estimation of Fracture Porosity in an Unsaturated Fractured Welded Tuff Using Gas Tracer Testing

    International Nuclear Information System (INIS)

    B.M. Freifeild

    2001-01-01

    Kinematic fracture porosity is an important hydrologic transport parameter for predicting the potential of rapid contaminant migration through fractured rock. The transport velocity of a solute moving within a fracture network is inversely related to the fracture porosity. Since fracture porosity is often one or two orders of magnitude smaller than matrix porosity, and fracture permeability is often orders of magnitude greater than matrix permeability, solutes may travel significantly faster in the fracture network than in the surrounding matrix. This dissertation introduces a new methodology for conducting gas tracer tests using a field portable mass spectrometer along with analytical tools for estimating fracture porosity using the measured tracer concentration breakthrough curves. Field experiments were conducted at Yucca Mountain, Nevada, consisting of air-permeability transient testing and gas-tracer-transport tests. The experiments were conducted from boreholes drilled within an underground tunnel as part of an investigation of rock mass hydrological behavior. Air-permeability pressure transients, recorded during constant mass flux injections, have been analyzed using a numerical inversion procedure to identify fracture permeability and porosity. Dipole gas tracer tests have also been conducted from the same boreholes used for air-permeability testing. Mass breakthrough data has been analyzed using a random walk particle-tracking model, with a dispersivity that is a function of the advective velocity. The estimated fracture porosity using the tracer test and air-injection test data ranges from .001 to .015. These values are an order of magnitude greater than the values estimated by others using hydraulically estimated fracture apertures. The estimates of porosity made using air-permeability test data are shown to be highly sensitive to formation heterogeneity. Uncertainty analyses performed on the gas tracer test results show high confidence in the parameter

  6. Fracture network growth for prediction of fracture characteristics and connectivity in tight reservoir rocks

    NARCIS (Netherlands)

    Barnhoorn, A.; Cox, S.F.

    2012-01-01

    Fracturing experiments on very low-porosity dolomite rocks shows a difference in growth of fracture networks by stress-driven fracturing and fluid-driven fracturing. Stress-driven fracture growth, in the absence of fluid pressure, initially forms fractures randomly throughout the rocks followed by

  7. Uncertainty in hydraulic tests in fractured rock

    International Nuclear Information System (INIS)

    Ji, Sung-Hoon; Koh, Yong-Kwon

    2014-01-01

    Interpretation of hydraulic tests in fractured rock has uncertainty because of the different hydraulic properties of a fractured rock to a porous medium. In this study, we reviewed several interesting phenomena which show uncertainty in a hydraulic test at a fractured rock and discussed their origins and the how they should be considered during site characterisation. Our results show that the estimated hydraulic parameters of a fractured rock from a hydraulic test are associated with uncertainty due to the changed aperture and non-linear groundwater flow during the test. Although the magnitude of these two uncertainties is site-dependent, the results suggest that it is recommended to conduct a hydraulic test with a little disturbance from the natural groundwater flow to consider their uncertainty. Other effects reported from laboratory and numerical experiments such as the trapping zone effect (Boutt, 2006) and the slip condition effect (Lee, 2014) can also introduce uncertainty to a hydraulic test, which should be evaluated in a field test. It is necessary to consider the way how to evaluate the uncertainty in the hydraulic property during the site characterisation and how to apply it to the safety assessment of a subsurface repository. (authors)

  8. Fractures and Rock Mechanics, Phase 1

    DEFF Research Database (Denmark)

    Krogsbøll, Anette; Jakobsen, Finn; Madsen, Lena

    1997-01-01

    The main objective of the project is to combine geological descriptions of fractures, chalk types and rock mechanical properties in order to investigate whether the chosen outcrops can be used as analogues to reservoir chalks. This report deals with 1) geological descriptions of outcrop locality...

  9. Fractures and Rock Mechanics, Phase 1

    DEFF Research Database (Denmark)

    Havmøller, Ole; Krogsbøll, Anette

    1997-01-01

    The main objectives of the project are to combine geological description of fractures, chalk types and rock mechanical properties, and to investigate whether the chosen outcrops can be used as analogues to reservoir chalks. Five chalk types, representing two outcrop localities: Stevns...

  10. Hydraulic fracturing in anisotropic and heterogeneous rocks

    NARCIS (Netherlands)

    Valliappan, V.; Remmers, J.J.C.; Barnhoorn, A.; Smeulders, D.M.J.

    2017-01-01

    In this paper, we present a two dimensional model for modelling the hydraulic fracture process in anisotropic and heterogeneous rocks. The model is formulated using extended finite elements (XFEM) in combination with Newton-Raphson method for spatial and Euler's implicit scheme for time. The

  11. Couple stresses and the fracture of rock.

    Science.gov (United States)

    Atkinson, Colin; Coman, Ciprian D; Aldazabal, Javier

    2015-03-28

    An assessment is made here of the role played by the micropolar continuum theory on the cracked Brazilian disc test used for determining rock fracture toughness. By analytically solving the corresponding mixed boundary-value problems and employing singular-perturbation arguments, we provide closed-form expressions for the energy release rate and the corresponding stress-intensity factors for both mode I and mode II loading. These theoretical results are augmented by a set of fracture toughness experiments on both sandstone and marble rocks. It is further shown that the morphology of the fracturing process in our centrally pre-cracked circular samples correlates very well with discrete element simulations. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  12. An exploration of unsaturated zone during in-situ heating test in sedimentary soft rocks

    International Nuclear Information System (INIS)

    Kubota, Kenji; Suzuki, Koichi; Ikenoya, Takafumi; Takakura, Nozomu; Tani, Kazuo

    2011-01-01

    In-situ heating test has been conducted to evaluate the influence of high temperature in an underground facility at a depth of 50 m. Resistivity monitoring is thought to be effective to map the extent of the high temperature and unsaturated zone. So we have conducted resistivity tomography during the heating test. As a result, the resistivity of the rock mass around the heating well was decreased and this area was gradually expanded from the heated area during the heating. This suggests that high temperature zone is detected by resistivity tomography. The results also suggested that resistivity was increased by unsaturation of rock mass around the heating well. (author)

  13. Numerical experiments on the probability of seepage into underground openings in heterogeneous fractured rock

    International Nuclear Information System (INIS)

    Birkholzer, J.; Li, G.; Tsang, C.F.; Tsang, Y.

    1998-01-01

    An important issue for the performance of underground nuclear waste repositories is the rate of seepage into the waste emplacement drifts. A prediction of this rate is particularly complicated for the potential repository site at Yucca Mountain, Nevada, because it is located in thick, unsaturated, fractured tuff formations. Underground opening in unsaturated media might act as capillary barriers, diverting water around them. In the present work, they study the potential rate of seepage into drifts as a function of the percolation flux at Yucca Mountain, based on a stochastic model of the fractured rock mass in the drift vicinity. A variety of flow scenarios are considered, assuming present-day and possible future climate conditions. They show that the heterogeneity in the flow domain is a key factor controlling seepage rates, since it causes channelized flow and local ponding in the unsaturated flow field

  14. Geometry, mechanics and transmissivity of rock fractures

    International Nuclear Information System (INIS)

    Lanaro, F.

    2001-04-01

    This thesis work investigates methods and tools for characterising, testing and modelling the behaviour of rock fractures. Using a 3D-laser-scanning technique, the topography of the surfaces and their position with respect to one another are measured. From the fracture topography, fracture roughness, angularity and aperture are quantified; the major features used for characterisation. The standard deviations for the asperity heights, surface slopes and aperture are determined. These statistical parameters usually increase/decrease according to power laws of the sampling size, and sometimes reach a sill beyond which they become constant. Also the number of contact spots with a certain area decreases according to a power-law function of the area. These power-law relations reveal the self affine fractal nature of roughness and aperture. Roughness is 'persistent' while aperture varies between 'persistent' and 'anti-persistent' probably depending on the degree of match of the fracture walls. The fractal models for roughness, aperture and contact area are used to develop a constitutive model, based on contact mechanics, for describing the fracture normal and shear deformability. The experimental testing results of normal deformability are simulated well by the model whereas fracture shear deformability is not as well modelled. The model predicts well fracture dilation but is too stiff compared to rock samples. A mathematical description of the aperture pattern during shearing is also formulated. The mean value and covariance of the aperture in shearing is calculated and verifies reported observations. The aperture map of samples is inserted in a numerical program for flow calculation. The 'integral transform method' is used for solving the Reynolds' equation; it transforms the fracture transmissivity pattern into a frequency-based function. This closely resembles the power laws that describe fractals. This function can be described directly from the fractal properties of

  15. Calculation of gas migration in fractured rock

    International Nuclear Information System (INIS)

    Thunvik, R.; Braester, C.

    1987-09-01

    Calculations are presented for rock properties characteristic to the Forsmark area. The rock permeability was determined by flow tests in vertical boreholes. It is assumed that the permeability distribution obtained from these boreholes is representative also for the permeability distribution along the repository cavern. Calculations were worked out for two different types of boundary conditions, one in which a constant gas flow rate equivalent to a gas production of 33000 kg/year was assumed and the other in which a constant gas cushion of 0.5 metres was assumed. For the permeability distribution considered, the breakthrough at the sea bottom occurred within one hour. The gaswater displacement took place mainly through the fractures of high permeability and practically no flow took place in the fractures of low permeability. (orig./DG)

  16. Improving estimates of subsurface gas transport in unsaturated fractured media using experimental Xe diffusion data and numerical methods

    Science.gov (United States)

    Ortiz, J. P.; Ortega, A. D.; Harp, D. R.; Boukhalfa, H.; Stauffer, P. H.

    2017-12-01

    Gas transport in unsaturated fractured media plays an important role in a variety of applications, including detection of underground nuclear explosions, transport from volatile contaminant plumes, shallow CO2 leakage from carbon sequestration sites, and methane leaks from hydraulic fracturing operations. Gas breakthrough times are highly sensitive to uncertainties associated with a variety of hydrogeologic parameters, including: rock type, fracture aperture, matrix permeability, porosity, and saturation. Furthermore, a couple simplifying assumptions are typically employed when representing fracture flow and transport. Aqueous phase transport is typically considered insignificant compared to gas phase transport in unsaturated fracture flow regimes, and an assumption of instantaneous dissolution/volatilization of radionuclide gas is commonly used to reduce computational expense. We conduct this research using a twofold approach that combines laboratory gas experimentation and numerical modeling to verify and refine these simplifying assumptions in our current models of gas transport. Using a gas diffusion cell, we are able to measure air pressure transmission through fractured tuff core samples while also measuring Xe gas breakthrough measured using a mass spectrometer. We can thus create synthetic barometric fluctuations akin to those observed in field tests and measure the associated gas flow through the fracture and matrix pore space for varying degrees of fluid saturation. We then attempt to reproduce the experimental results using numerical models in PLFOTRAN and FEHM codes to better understand the importance of different parameters and assumptions on gas transport. Our numerical approaches represent both single-phase gas flow with immobile water, as well as full multi-phase transport in order to test the validity of assuming immobile pore water. Our approaches also include the ability to simulate the reaction equilibrium kinetics of dissolution

  17. Evaluation of permeable fractures in rock aquifers

    Science.gov (United States)

    Bok Lee, Hang

    2015-04-01

    In this study, the practical usefulness and fundamental applicability of a self-potential (SP) method for identifying the permeable fractures were evaluated by a comparison of SP methods with other geophysical logging methods and hydraulic tests. At a 10 m-shallow borehole in the study site, the candidates of permeable fractures crossing the borehole were first determined by conventional geophysical methods such as an acoustic borehole televiwer, temperature, electrical conductivity and gamma-gamma loggings, which was compared to the analysis by the SP method. Constant pressure injection and recovery tests were conducted for verification of the hydraulic properties of the fractures identified by various logging methods. The acoustic borehole televiwer and gamma-gamma loggings detected the open space or weathering zone within the borehole, but they cannot prove the possibility of a groundwater flow through the detected fractures. The temperature and electrical conductivity loggings had limitations to detect the fractured zones where groundwater in the borehole flows out to the surrounding rock aquifers. Comparison of results from different methods showed that there is a best correlation between the distribution of hydraulic conductivity and the variation of the SP signals, and the SP logging can estimate accurately the hydraulic activity as well as the location of permeable fractures. Based on the results, the SP method is recommended for determining the hydraulically-active fractures rather than other conventional geophysical loggings. This self-potential method can be effectively applied in the initial stage of a site investigation which selects the optimal location and evaluates the hydrogeological property of fractures in target sites for the underground structure including the geothermal reservoir and radioactive waste disposal.

  18. Anisotropic characterization of rock fracture surfaces subjected to profile analysis

    International Nuclear Information System (INIS)

    Zhou, H.W.; Xie, H.

    2004-01-01

    The mechanical parameters of a rock fracture are dependent on its surface roughness anisotropy. In this Letter, we show how quantitatively describe the anisotropy of a rock fracture surface. A parameter, referred to as the index for the accumulation power spectral density psd*, is proposed to characterize the anisotropy of a rock fracture surface. Variation of psd*, with orientation angle θ of sampling, is also discussed

  19. Maximum likelihood Bayesian averaging of airflow models in unsaturated fractured tuff using Occam and variance windows

    NARCIS (Netherlands)

    Morales-Casique, E.; Neuman, S.P.; Vesselinov, V.V.

    2010-01-01

    We use log permeability and porosity data obtained from single-hole pneumatic packer tests in six boreholes drilled into unsaturated fractured tuff near Superior, Arizona, to postulate, calibrate and compare five alternative variogram models (exponential, exponential with linear drift, power,

  20. Wetting front instability in an initially wet unsaturated fracture

    International Nuclear Information System (INIS)

    Nicholl, M.J.; Glass, R.J.; Nguyen, H.A.

    1993-01-01

    Experimental results exploring gravity-driven wetting from instability in a pre-wetted, rough-walled analog fractures such as those at Yucca Mountain are presented. Initial conditions considered include a uniform moisture field wetted to field capacity of the analog fracture and the structured moisture field created by unstable infiltration into an initially dry fracture. As in previous studies performed under dry initial conditions, instability was found to result both at the cessation of stable infiltration and at flux lower than the fracture capacity under gravitational driving force. Individual fingers were faster, narrower, longer, and more numerous than observed under dry initial conditions. Wetting fronts were found to follow existing wetted structure, providing a mechanism for rapid recharge and transport

  1. Wetting front instability in an initially wet unsaturated fracture

    International Nuclear Information System (INIS)

    Nicholl, M.J.; Glass, R.J.; Nguyen, H.A.

    1992-01-01

    Experimental results exploring gravity-driven wetting front instability in a pre-wetted, rough-walled analog fracture are presented. Initial conditions considered include a uniform moisture field wetted to field capacity of the analog fracture and the structured moisture field created by unstable infiltration into an initially dry fracture. As in previous studies performed under dry initial conditions, instability was found to result both at the cessation of stable infiltration and at flux lower than the fracture capacity under gravitational driving force. Individual fingers were faster, narrower, longer, and more numerous than observed under dry initial conditions. Wetting fronts were found to follow existing wetted structure, providing a mechanism for rapid recharge and transport

  2. Concepts of flow in fractured rocks

    International Nuclear Information System (INIS)

    Black, J.H.

    1989-01-01

    The role of well testing is considered in the context of tracer tests in fractured rock. It is shown that the important information required by a tracer test includes not just the hydrogeological parameters (transmissivity and storage), but also the geometry of flow. This is usually implicit in well testing, perhaps because the tests are generally interpretationally insensitive to variations in flow geometry. It is also argued that both well and tracer tests change their flow geometry during their lifetime. They often start as pipe flow near a well and change to large scale, almost spherical, flow after long periods of time. The duration of a tracer test is compared with that of a well test and is found to reach an equivalent duration (of dimensionless time) that is at least 10 4 times longer. Care should be exercised in transposing flow geometries derived from mature well tests on to tracer tests which are not similar in dimensionless time. Finally, a 'sinusoidal flow test' is outlined which has prompted a new way of looking at well tests in terms of their flow geometry. The new analysis involves 'partial dimension' of flow and is probably highly appropriate to fissured rocks. Fissured rocks have, for too long, been seen as a regular system of planar, fully transmissive fissures. (author). 12 refs, 4 figs, 1 tab

  3. A numerical study of water percolation through an unsaturated variable aperture fracture under coupled thermomechanical effects

    International Nuclear Information System (INIS)

    Tsang, C.F.; Noorishad, J.; Hale, F.V.

    1991-12-01

    In calculation of ground water travel times associated with performance assessment of a nuclear waste repository, the role of fractures may turn out to be very important. There are two aspects related to fracture flow that have not been fully resolved. The first is the effect of coupled thermomechanical impact on fracture apertures due to the thermal output of the nuclear waste repository. The second is the effect of the variable aperture nature of the fractures. The present paper is an exploratory study of the impact of these two effects on water percolation through unsaturated fractures. The paper is divided into two main sections. the first section describes a calculation of the thermomechanical behavior of the geologic formation around a waste repository. In this exploratory study we assume two major fractures, one vertical and one horizontal through the repository center. Temperatures and thermally induced stress fields are calculated. The second part of the paper considers the unsaturated case and describes a study of water infiltration from the land surface through the vertical fracture to the repository

  4. Aquifer Recharge Estimation In Unsaturated Porous Rock Using Darcian And Geophysical Methods.

    Science.gov (United States)

    Nimmo, J. R.; De Carlo, L.; Masciale, R.; Turturro, A. C.; Perkins, K. S.; Caputo, M. C.

    2016-12-01

    Within the unsaturated zone a constant downward gravity-driven flux of water commonly exists at depths ranging from a few meters to tens of meters depending on climate, medium, and vegetation. In this case a steady-state application of Darcy's law can provide recharge rate estimates.We have applied an integrated approach that combines field geophysical measurements with laboratory hydraulic property measurements on core samples to produce accurate estimates of steady-state aquifer recharge, or, in cases where episodic recharge also occurs, the steady component of recharge. The method requires (1) measurement of the water content existing in the deep unsaturated zone at the location of a core sample retrieved for lab measurements, and (2) measurement of the core sample's unsaturated hydraulic conductivity over a range of water content that includes the value measured in situ. Both types of measurements must be done with high accuracy. Darcy's law applied with the measured unsaturated hydraulic conductivity and gravitational driving force provides recharge estimates.Aquifer recharge was estimated using Darcian and geophysical methods at a deep porous rock (calcarenite) experimental site in Canosa, southern Italy. Electrical Resistivity Tomography (ERT) and Vertical Electrical Sounding (VES) profiles were collected from the land surface to water table to provide data for Darcian recharge estimation. Volumetric water content was estimated from resistivity profiles using a laboratory-derived calibration function based on Archie's law for rock samples from the experimental site, where electrical conductivity of the rock was related to the porosity and water saturation. Multiple-depth core samples were evaluated using the Quasi-Steady Centrifuge (QSC) method to obtain hydraulic conductivity (K), matric potential (ψ), and water content (θ) estimates within this profile. Laboratory-determined unsaturated hydraulic conductivity ranged from 3.90 x 10-9 to 1.02 x 10-5 m

  5. Study of deep fracturation of granitic rock mass. Documentary study

    International Nuclear Information System (INIS)

    Bles, J.L.; Landry, J.

    1984-01-01

    This documentary study realized with the financial support of the European Communities and the CEA aims at the utilization of available data for the understanding of the evolution of natural fractures in granitic rocks from the surface to deep underground. The Mt Blanc road tunnel, the EDF's Arc-Isere gallerie, the Auriat deep borehole and the Pyrenean rock mass of Bassies are studied because detailed structural and geological studies have been realized these last 20 years. In this study are more particularly analyzed the relationship between small fractures and large faults, evolution with depth of fracture density and direction, consequences of rock decompression and relationship between fracturation and groundwater

  6. Two-phase flow in fractured rock

    International Nuclear Information System (INIS)

    Davies, P.; Long, J.; Zuidema, P.

    1993-11-01

    This report gives the results of a three-day workshop on two-phase flow in fractured rock. The workshop focused on two-phase flow processes that are important in geologic disposal of nuclear waste as experienced in a variety of repository settings. The goals and objectives of the workshop were threefold: exchange information; describe the current state of understanding; and identify research needs. The participants were divided into four subgroups. Each group was asked to address a series of two-phase flow processes. The following groups were defined to address these processes: basic flow processes; fracture/matrix interactions; complex flow processes; and coupled processes. For each process, the groups were asked to address these four issues: (1) describe the two-phase flow processes that are important with respect to repository performance; (2) describe how this process relates to the specific driving programmatic issues given above for nuclear waste storage; (3) evaluate the state of understanding for these processes; and (4) suggest additional research to address poorly understood processes relevant to repository performance. The reports from each of the four working groups are given here

  7. Folding and Fracturing of Rocks: the background

    Science.gov (United States)

    Ramsay, John G.

    2017-04-01

    This book was generated by structural geology teaching classes at Imperial College. I was appointed lecturer during 1957 and worked together with Dr Gilbert Wilson teaching basic structural geology at B.Sc level. I became convinced that the subject, being essentially based on geometric field observations, required a firm mathematical basis for its future development. In particular it seemed to me to require a very sound understanding of stress and strain. My field experience suggested that a knowledge of two- and three-demensional strain was critical in understanding natural tectonic processes. I found a rich confirmation for this in early publications of deformed fossils, oolitic limestones and spotted slates made by several geologists around the beginning of the 20th century (Sorby, Philips, Haughton, Harker) often using surprisingly sophisticated mathematical methods. These methods were discussed and elaborated in Folding and Fracturing of Rocks in a practical way. The geometric features of folds were related to folding mechanisms and the fold related small scale structures such as cleavage, schistosity and lineation explained in terms of rock strain. My work in the Scottish Highlands had shown just how repeated fold superposition could produce very complex geometric features, while further work in other localities suggested that such geometric complications are common in many orogenic zones. From the development of structural geological studies over the past decades it seems that the readers of this book have found many of the ideas set out are still of practical application. The mapping of these outcrop-scale structures should be emphasised in all field studies because they can be seen as ''fingerprints'' of regional scale tectonic processes. My own understanding of structural geology has been inspired by field work and I am of the opinion that future progress in understanding will be likewise based on careful observation and measurement of the features of

  8. Approaches to large scale unsaturated flow in heterogeneous, stratified, and fractured geologic media

    International Nuclear Information System (INIS)

    Ababou, R.

    1991-08-01

    This report develops a broad review and assessment of quantitative modeling approaches and data requirements for large-scale subsurface flow in radioactive waste geologic repository. The data review includes discussions of controlled field experiments, existing contamination sites, and site-specific hydrogeologic conditions at Yucca Mountain. Local-scale constitutive models for the unsaturated hydrodynamic properties of geologic media are analyzed, with particular emphasis on the effect of structural characteristics of the medium. The report further reviews and analyzes large-scale hydrogeologic spatial variability from aquifer data, unsaturated soil data, and fracture network data gathered from the literature. Finally, various modeling strategies toward large-scale flow simulations are assessed, including direct high-resolution simulation, and coarse-scale simulation based on auxiliary hydrodynamic models such as single equivalent continuum and dual-porosity continuum. The roles of anisotropy, fracturing, and broad-band spatial variability are emphasized. 252 refs

  9. Conceptualization of a hypothetical high-level nuclear waste repository site in unsaturated, fractured tuff

    International Nuclear Information System (INIS)

    Parsons, A.M.; Olague, N.E.; Gallegos, D.P.

    1991-01-01

    Under the sponsorship of the US Nuclear Regulatory Commission (NRC), Sandia National Laboratories (SNL) is developing a performance assessment methodology for the analysis of long-term disposal and isolation of high-level nuclear wastes (HLW) in alternative geologic media. As part of this exercise, SNL created a conceptualization of ground-water flow and radionuclide transport in the far field of a hypothetical HLW repository site located in unsaturated, fractured tuff formations. This study provides a foundation for the development of conceptual mathematical, and numerical models to be used in this performance assessment methodology. This conceptualization is site specific in terms of geometry, the regional ground-water flow system, stratigraphy, and structure in that these are based on information from Yucca Mountain located on the Nevada Test Site. However, in terms of processes in unsaturated, fractured, porous media, the model is generic. This report also provides a review and evaluation of previously proposed conceptual models of unsaturated and saturated flow and solute transport. This report provides a qualitative description of a hypothetical HLW repository site in fractured tuff. However, evaluation of the current knowledge of flow and transport at Yucca Mountain does not yield a single conceptual model. Instead, multiple conceptual models are possible given the existing information

  10. Conceptualization of a hypothetical high-level nuclear waste repository site in unsaturated, fractured tuff

    Energy Technology Data Exchange (ETDEWEB)

    Parsons, A.M.; Olague, N.E.; Gallegos, D.P. [Sandia National Labs., Albuquerque, NM (USA)

    1991-01-01

    Under the sponsorship of the US Nuclear Regulatory Commission (NRC), Sandia National Laboratories (SNL) is developing a performance assessment methodology for the analysis of long-term disposal and isolation of high-level nuclear wastes (HLW) in alternative geologic media. As part of this exercise, SNL created a conceptualization of ground-water flow and radionuclide transport in the far field of a hypothetical HLW repository site located in unsaturated, fractured tuff formations. This study provides a foundation for the development of conceptual mathematical, and numerical models to be used in this performance assessment methodology. This conceptualization is site specific in terms of geometry, the regional ground-water flow system, stratigraphy, and structure in that these are based on information from Yucca Mountain located on the Nevada Test Site. However, in terms of processes in unsaturated, fractured, porous media, the model is generic. This report also provides a review and evaluation of previously proposed conceptual models of unsaturated and saturated flow and solute transport. This report provides a qualitative description of a hypothetical HLW repository site in fractured tuff. However, evaluation of the current knowledge of flow and transport at Yucca Mountain does not yield a single conceptual model. Instead, multiple conceptual models are possible given the existing information.

  11. Hydrological and thermal issues concerning a nuclear waste repository in fractured rocks

    International Nuclear Information System (INIS)

    Wang, J.S.Y.

    1991-12-01

    The characterization of the ambient conditions of a potential site and the assessment of the perturbations induced by a nuclear waste repository require hydrological and thermal investigations of the geological formations at different spatial and temporal scales. For high-level wastes, the near-field impacts depend on the heat power of waste packages and the far-field long-term perturbations depend on the cumulative heat released by the emplaced wastes. Surface interim storage of wastes for several decades could lower the near-field impacts but would have relatively small long-term effects if spent fuels were the waste forms for the repository. One major uncertainty in the assessment of repository impacts is from the variation of hydrological properties in heterogeneous media, including the effects of fractures as high-permeability flow paths for containment migration. Under stress, a natural fracture cannot be represented by the parallel plate model. The rock surface roughness, the contact area, and the saturation state in the rock matrix could significantly change the fracture flow. In recent years, the concern of fast flow through fractures in saturated media has extended to the unsaturated zones. The interactions at different scales between fractures and matrix, between fractured matrix unites and porous units, and between formations and faults are discussed

  12. Multiple tracing experiments in unsaturated fractured clayey till

    DEFF Research Database (Denmark)

    Mortensen, Annette Pia; Jensen, Karsten Høgh; Nilsson, B.

    2004-01-01

    control of the water balance in the block. Experiments at three different steady-state flow rates were performed. Multiple tracers with different diffusion coefficients were applied in each experiment to evaluate the influence of diffusive exchange between fractures and the matrix. The tracers included...... a fast peak was followed by a long tailing period. At flow rates, two of the applied tracers revealed a double peak breakthrough curve, whereas the tracer with the lowest molecular diffusion coefficient showed only one peak. The separation of the tracers was hypothesized to be influenced by extensive...... two halogen anions ( Cl- and Br-), two fluorobenzoic acids (FBA) ( 2,3-DFBA and 2,6-DFBA), two fluorescent dyes (uranine and sulforhodamine B), and one colloidal tracer (0.5-mum mlatex particles). At high flow rates, the obtained tracer breakthrough showed a traditional asymmetrical behavior where...

  13. Simulating Hydraulic Fracturing: Failure in soft versus hard rocks

    Science.gov (United States)

    Aleksans, J.; Koehn, D.; Toussaint, R.

    2017-12-01

    In this contribution we discuss the dynamic development of hydraulic fractures, their evolution and the resulting seismicity during fluid injection in a coupled numerical model. The model describes coupling between a solid that can fracture dynamically and a compressible fluid that can push back at the rock and open fractures. With a series of numerical simulations we show how the fracture pattern and seismicity change depending on changes in depth, injection rate, Young's Modulus and breaking strength. Our simulations indicate that the Young's Modulus has the largest influence on the fracture dynamics and also the related seismicity. Simulations of rocks with a Young's modulus smaller than 10 GPa show dominant mode I failure and a growth of fracture aperture with a decrease in Young's modulus. Simulations of rocks with a higher Young's modulus than 10 GPa show fractures with a constant aperture and fracture growth that is mainly governed by a growth in crack length and an increasing amount of mode II failure. We propose that two distinct failure regimes are observed in the simulations, above 10 GPa rocks break with a constant critical stress intensity factor whereas below 10 GPa they break reaching a critical cohesion, i.e. a critical tensile strength. These results are very important for the prediction of fracture dynamics and seismicity during fluid injection, especially since we see a transition from one failure regime to another at around 10 GPa, a Young's modulus that lies in the middle of possible values for natural shale rocks.

  14. An integrated methodology for characterizing flow and transport processes in fractured rock

    International Nuclear Information System (INIS)

    Wu, Yu-Shu

    2007-01-01

    To investigate the coupled processes involved in fluid and heat flow and chemical transport in the highly heterogeneous, unsaturated-zone (UZ) fractured rock of Yucca Mountain, we present an integrated modeling methodology. This approach integrates a wide variety of moisture, pneumatic, thermal, and geochemical isotopic field data into a comprehensive three-dimensional numerical model for modeling analyses. The results of field applications of the methodology show that moisture data, such as water potential and liquid saturation, are not sufficient to determine in situ percolation flux, whereas temperature and geochemical isotopic data provide better constraints to net infiltration rates and flow patterns. In addition, pneumatic data are found to be extremely valuable in estimating large-scale fracture permeability. The integration of hydrologic, pneumatic, temperature, and geochemical data into modeling analyses is thereby demonstrated to provide a practical modeling approach for characterizing flow and transport processes in complex fractured formations

  15. Impact of bimodal textural heterogeneity and connectivity on flow and transport through unsaturated mine waste rock

    Science.gov (United States)

    Appels, Willemijn M.; Ireson, Andrew M.; Barbour, S. Lee

    2018-02-01

    Mine waste rock dumps have highly variable flowpaths caused by contrasting textures and geometry of materials laid down during the 'plug dumping' process. Numerical experiments were conducted to investigate how these characteristics control unsaturated zone flow and transport. Hypothetical profiles of inner-lift structure were generated with multiple point statistics and populated with hydraulic parameters of a finer and coarser material. Early arrival of water and solutes at the bottom of the lifts was observed after spring snowmelt. The leaching efficiency, a measure of the proportion of a resident solute that is flushed out of the rock via infiltrating snowmelt or rainfall, was consistently high, but modified by the structure and texture of the lift. Under high rates of net percolation during snowmelt, preferential flow was generated in coarse textured part of the rock, and solutes in the fine textured parts of the rock remained stagnant. Under lower rates of net percolation during the summer and fall, finer materialswere flushed too, and the spatial variability of solute concentration in the lift was reduced. Layering of lifts leads to lower flow rates at depth, minimizing preferential flow and increased leaching of resident solutes. These findings highlight the limited role of large scale connected geometries on focusing flow and transport under dynamic surface net percolation conditions. As such, our findings agree with recent numerical results from soil studies with Gaussian connected geometries as well as recent experimental findings, emphasizing the dominant role of matrix flow and high leaching efficiency in large waste rock dumps.

  16. An XFEM Model for Hydraulic Fracturing in Partially Saturated Rocks

    Directory of Open Access Journals (Sweden)

    Salimzadeh Saeed

    2016-01-01

    Full Text Available Hydraulic fracturing is a complex multi-physics phenomenon. Numerous analytical and numerical models of hydraulic fracturing processes have been proposed. Analytical solutions commonly are able to model the growth of a single hydraulic fracture into an initially intact, homogeneous rock mass. Numerical models are able to analyse complex problems such as multiple hydraulic fractures and fracturing in heterogeneous media. However, majority of available models are restricted to single-phase flow through fracture and permeable porous rock. This is not compatible with actual field conditions where the injected fluid does not have similar properties as the host fluid. In this study we present a fully coupled hydro-poroelastic model which incorporates two fluids i.e. fracturing fluid and host fluid. Flow through fracture is defined based on lubrication assumption, while flow through matrix is defined as Darcy flow. The fracture discontinuity in the mechanical model is captured using eXtended Finite Element Method (XFEM while the fracture propagation criterion is defined through cohesive fracture model. The discontinuous matrix fluid velocity across fracture is modelled using leak-off loading which couples fracture flow and matrix flow. The proposed model has been discretised using standard Galerkin method, implemented in Matlab and verified against several published solutions. Multiple hydraulic fracturing simulations are performed to show the model robustness and to illustrate how problem parameters such as injection rate and rock permeability affect the hydraulic fracturing variables i.e. injection pressure, fracture aperture and fracture length. The results show the impact of partial saturation on leak-off and the fact that single-phase models may underestimate the leak-off.

  17. Hydromechanical modeling of clay rock including fracture damage

    Science.gov (United States)

    Asahina, D.; Houseworth, J. E.; Birkholzer, J. T.

    2012-12-01

    Argillaceous rock typically acts as a flow barrier, but under certain conditions significant and potentially conductive fractures may be present. Fracture formation is well-known to occur in the vicinity of underground excavations in a region known as the excavation disturbed zone. Such problems are of particular importance for low-permeability, mechanically weak rock such as clays and shales because fractures can be relatively transient as a result of fracture self-sealing processes. Perhaps not as well appreciated is the fact that natural fractures can form in argillaceous rock as a result of hydraulic overpressure caused by phenomena such as disequlibrium compaction, changes in tectonic stress, and mineral dehydration. Overpressure conditions can cause hydraulic fracturing if the fluid pressure leads to tensile effective stresses that exceed the tensile strength of the material. Quantitative modeling of this type of process requires coupling between hydrogeologic processes and geomechanical processes including fracture initiation and propagation. Here we present a computational method for three-dimensional, hydromechanical coupled processes including fracture damage. Fractures are represented as discrete features in a fracture network that interact with a porous rock matrix. Fracture configurations are mapped onto an unstructured, three-dimensonal, Voronoi grid, which is based on a random set of spatial points. Discrete fracture networks (DFN) are represented by the connections of the edges of a Voronoi cells. This methodology has the advantage that fractures can be more easily introduced in response to coupled hydro-mechanical processes and generally eliminates several potential issues associated with the geometry of DFN and numerical gridding. A geomechanical and fracture-damage model is developed here using the Rigid-Body-Spring-Network (RBSN) numerical method. The hydrogelogic and geomechanical models share the same geometrical information from a 3D Voronoi

  18. Deep fracturation of granitic rock mass. Fracturation profonde des massifs rocheux granitiques

    Energy Technology Data Exchange (ETDEWEB)

    Bles, J L; Blanchin, R; Bonijoly, D; Dutartre, P; Feybesse, J L; Gros, Y; Landry, J; Martin, P

    1986-01-01

    This documentary study realized with the financial support of the European Communities and the CEA aims at the utilization of available data for the understanding of the evolution of natural fractures in granitic rocks from the surface to deep underground, in various feasibility studies dealing with radioactive wastes disposal. The Mont Blanc road tunnel, the EDF Arc-Isere gallerie, the Auriat deep borehole and the Pyrenean rock mass of Bassies are studied. In this study are more particularly analyzed the relationship between small fractures and large faults, evolution with depth of fracture density and direction, consequences of rock decompression and relationship between fracturation and groundwater.

  19. Effects of fracture distribution and length scale on the equivalent continuum elastic compliance of fractured rock masses

    Directory of Open Access Journals (Sweden)

    Marte Gutierrez

    2015-12-01

    Full Text Available Fracture systems have strong influence on the overall mechanical behavior of fractured rock masses due to their relatively lower stiffness and shear strength than those of the rock matrix. Understanding the effects of fracture geometrical distribution, such as length, spacing, persistence and orientation, is important for quantifying the mechanical behavior of fractured rock masses. The relation between fracture geometry and the mechanical characteristics of the fractured rock mass is complicated due to the fact that the fracture geometry and mechanical behaviors of fractured rock mass are strongly dependent on the length scale. In this paper, a comprehensive study was conducted to determine the effects of fracture distribution on the equivalent continuum elastic compliance of fractured rock masses over a wide range of fracture lengths. To account for the stochastic nature of fracture distributions, three different simulation techniques involving Oda's elastic compliance tensor, Monte Carlo simulation (MCS, and suitable probability density functions (PDFs were employed to represent the elastic compliance of fractured rock masses. To yield geologically realistic results, parameters for defining fracture distributions were obtained from different geological fields. The influence of the key fracture parameters and their relations to the overall elastic behavior of the fractured rock mass were studied and discussed. A detailed study was also carried out to investigate the validity of the use of a representative element volume (REV in the equivalent continuum representation of fractured rock masses. A criterion was also proposed to determine the appropriate REV given the fracture distribution of the rock mass.

  20. Analysis of compressive fracture in rock using statistical techniques

    Energy Technology Data Exchange (ETDEWEB)

    Blair, S.C.

    1994-12-01

    Fracture of rock in compression is analyzed using a field-theory model, and the processes of crack coalescence and fracture formation and the effect of grain-scale heterogeneities on macroscopic behavior of rock are studied. The model is based on observations of fracture in laboratory compression tests, and incorporates assumptions developed using fracture mechanics analysis of rock fracture. The model represents grains as discrete sites, and uses superposition of continuum and crack-interaction stresses to create cracks at these sites. The sites are also used to introduce local heterogeneity. Clusters of cracked sites can be analyzed using percolation theory. Stress-strain curves for simulated uniaxial tests were analyzed by studying the location of cracked sites, and partitioning of strain energy for selected intervals. Results show that the model implicitly predicts both development of shear-type fracture surfaces and a strength-vs-size relation that are similar to those observed for real rocks. Results of a parameter-sensitivity analysis indicate that heterogeneity in the local stresses, attributed to the shape and loading of individual grains, has a first-order effect on strength, and that increasing local stress heterogeneity lowers compressive strength following an inverse power law. Peak strength decreased with increasing lattice size and decreasing mean site strength, and was independent of site-strength distribution. A model for rock fracture based on a nearest-neighbor algorithm for stress redistribution is also presented and used to simulate laboratory compression tests, with promising results.

  1. Experimental and Numerical Investigation of Rock Dynamic Fracture

    Directory of Open Access Journals (Sweden)

    Aliasghar Mirmohammadlou

    2017-06-01

    Full Text Available Rapid development of engineering activities expands through a variety of rock engineering processes such as drilling, blasting, mining and mineral processing. These activities require rock dynamic fracture mechanics method to characterize the rock behavior. Dynamic fracture toughness is an important parameter for the analysis of engineering structures under dynamic loading. Several experimental methods are used for determination of dynamic fracture properties of materials. Among them, the Hopkinson pressure bar and the drop weight have been frequently used for rocks. On the other hand, numerical simulations are very useful in dynamic fracture studies. Among vast variety of numerical techniques, the powerful extended finite element method (XFEM enriches the finite element approximation with appropriate functions extracted from the fracture mechanics solution around a crack-tip. The main advantage of XFEM is its capability in modeling different on a fixed mesh, which can be generated without considering the existence of discontinuities. In this paper, first, the design of a drop weight test setup is presented. Afterwards, the experimental tests on igneous (basalt and calcareous (limestone rocks with single-edge-cracked bend specimen are discussed. Then, each experimental test is modeled with the XFEM code. Finally, the obtained experimental and numerical results are compared. The results indicate that the experimentally predicted dynamic fracture toughness has less than 8 percent difference with calculated dynamic fracture toughness from extended finite element method

  2. Solute transport in fractured rock - applications to radionuclide waste repositories

    International Nuclear Information System (INIS)

    Neretnieks, I.

    1990-12-01

    Flow and solute transport in fractured rocks has been intensively studied in the last decade. The increased interest is mainly due to the plans in many countries to site repositories for high level nuclear waste in deep geologic formations. All investigated crystalline rocks have been found to be fractured and most of the water flows in the fractures and fracture zones. The water transports dissolved species and radionuclides. It is thus of interest to be able to understand and to do predictive modelling of the flowrate of water, the flowpaths and the residence times of the water and of the nuclides. The dissolved species including the nuclides will interact with the surrounding rock in different ways and will in many cases be strongly retarded relative to the water velocity. Ionic species may be ion exchanged or sorbed in the mineral surfaces. Charges and neutral species may diffuse into the stagnant waters in the rock matrix and thus be withdrawn from the mobile water. These effects will be strongly dependent on how much rock surface is in contact with the flowing water. It has been found in a set of field experiments and by other observations that not all fractures conduct water. Furthermore it is found that conductive fractures only conduct the water in a small part of the fracture in what is called channels or preferential flowpaths. This report summarizes the present concepts of water flow and solute transport in fractured rocks. The data needs for predictive modelling are discussed and both field and laboratory measurement which have been used to obtain data are described. Several large scale field experiments which have been specially designed to study flow and tracer transport in crystalline rocks are described. In many of the field experients new techniques have been developed and used. (81 refs.) (author)

  3. Fracturing process and effect of fracturing degree on wave velocity of a crystalline rock

    Directory of Open Access Journals (Sweden)

    Charalampos Saroglou

    2017-10-01

    Full Text Available The present paper investigates the effect of fracturing degree on P- and S-wave velocities in rock. The deformation of intact brittle rocks under loading conditions is characterized by a microcracking procedure, which occurs due to flaws in their microscopic structure and propagates through the intact rock, leading to shear fracture. This fracturing process is of fundamental significance as it affects the mechanical properties of the rock and hence the wave velocities. In order to determine the fracture mechanism and the effect of fracturing degree, samples were loaded at certain percentages of peak strength and ultrasonic wave velocity was recorded after every test. The fracturing degree was recorded on the outer surface of the sample and quantified by the use of the indices P10 (traces of joints/m, P20 (traces of joints/m2 and P21 (length of fractures/m2. It was concluded that the wave velocity decreases exponentially with increasing fracturing degree. Additionally, the fracturing degree is described adequately with the proposed indices. Finally, other parameters concerning the fracture characteristics, rock type and scale influence were found to contribute to the velocity decay and need to be investigated further.

  4. Laboratory investigations into fracture propagation characteristics of rock material

    Science.gov (United States)

    Prasad, B. N. V. Siva; Murthy, V. M. S. R.

    2018-04-01

    After Industrial Revolution, demand of materials for building up structures have increased enormously. Unfortunately, failures of such structures resulted in loss of life and property. Rock is anisotropic and discontinuous in nature with inherent flaws or so-called discontinuities in it. Rock is apparently used for construction in mining, civil, tunnelling, hydropower, geothermal and nuclear sectors [1]. Therefore, the strength of the structure built up considering rockmass as the construction material needs proper technical evaluation during designing stage itself to prevent and predict the scenarios of catastrophic failures due to these inherent fractures [2]. In this study, samples collected from nine different drilling sites have been investigated in laboratory for understanding the fracture propagation characteristics in rock. Rock material properties, ultrasonic velocities through pulse transmission technique and Mode I Fracture Toughness Testing of different variants of Dolomites and Graywackes are determined in laboratory and the resistance of the rock material to catastrophic crack extension or propagation has been determined. Based on the Fracture Toughness values and the rock properties, critical Energy Release Rates have been estimated. However further studies in this direction is to be carried out to understand the fracture propagation characteristics in three-dimensional space.

  5. Thermo-hydro-mechanical behavior of fractured rock mass

    International Nuclear Information System (INIS)

    Coste, F.

    1997-12-01

    The purpose of this research is to model Thermo-Hydro-Mechanical behavior of fractured rock mass regarding a nuclear waste re-depository. For this, a methodology of modeling was proposed and was applied to a real underground site (EDF site at Nouvelle Romanche). This methodology consists, in a first step, to determine hydraulic and mechanical REV. Beyond the greatest of these REV, development of a finite element code allows to model all the fractures in an explicit manner. The homogenized mechanical properties are determined in drained and undrained boundary conditions by simulating triaxial tests that represent rock mass subject to loading. These simulations allow to study the evolution of hydraulic and mechanical properties as a function of stress state. Drained and undrained boundary conditions enable to discuss the validity of assimilation of a fractured rock mass to a porous medium. The simulations lead to a better understanding of the behavior of the fractured rock masses and allow to show the dominant role of the shear behavior of the fractures on the hydraulic and mechanical homogenized properties. From a thermal point of view, as long as conduction is dominant, thermal properties of the rock mass are almost the same as those the intact rock. (author)

  6. On the infiltration of a liquid front in an unsaturated, fractured porous medium

    International Nuclear Information System (INIS)

    Nitao, J.; Buscheck, T.

    1989-08-01

    The unsaturated zone at Yucca Mountain, Nevada, is currently under scientific investigation as a proposed site for the permanent storage of high-level nuclear waste. A deeper understanding of fracture-matrix interaction needed for the prediction of water movement around an in the repository. We show that the liquid front movement can be classified into physically interpretable, distinctive flow regimes. Asymptotic solutions for the front movement are given for each flow period and comparisons with numerical solutions are made. In addition to applications in nuclear waste storage, the results of our study is relevant to hazardous waste disposal, petroleum recovery, and flow in soil macropores. 17 refs., 13 figs., 6 tabs

  7. Numerical simulations of seepage flow in rough single rock fractures

    Directory of Open Access Journals (Sweden)

    Qingang Zhang

    2015-09-01

    Full Text Available To investigate the relationship between the structural characteristics and seepage flow behavior of rough single rock fractures, a set of single fracture physical models were produced using the Weierstrass–Mandelbrot functions to test the seepage flow performance. Six single fractures, with various surface roughnesses characterized by fractal dimensions, were built using COMSOL multiphysics software. The fluid flow behavior through the rough fractures and the influences of the rough surfaces on the fluid flow behavior was then monitored. The numerical simulation indicates that there is a linear relationship between the average flow velocity over the entire flow path and the fractal dimension of the rough surface. It is shown that there is good a agreement between the numerical results and the experimental data in terms of the properties of the fluid flowing through the rough single rock fractures.

  8. Quantifying water flow and retention in an unsaturated fracture-facial domain

    Science.gov (United States)

    Nimmo, John R.; Malek-Mohammadi, Siamak

    2015-01-01

    Hydrologically significant flow and storage of water occur in macropores and fractures that are only partially filled. To accommodate such processes in flow models, we propose a three-domain framework. Two of the domains correspond to water flow and water storage in a fracture-facial region, in addition to the third domain of matrix water. The fracture-facial region, typically within a fraction of a millimeter of the fracture wall, includes a flowing phase whose fullness is determined by the availability and flux of preferentially flowing water, and a static storage portion whose fullness is determined by the local matric potential. The flow domain can be modeled with the source-responsive preferential flow model, and the roughness-storage domain can be modeled with capillary relations applied on the fracture-facial area. The matrix domain is treated using traditional unsaturated flow theory. We tested the model with application to the hydrology of the Chalk formation in southern England, coherently linking hydrologic information including recharge estimates, streamflow, water table fluctuation, imaging by electron microscopy, and surface roughness. The quantitative consistency of the three-domain matrix-microcavity-film model with this body of diverse data supports the hypothesized distinctions and active mechanisms of the three domains and establishes the usefulness of this framework.

  9. Diffusivity and electrical resistivity measurements in rock matrix around fractures

    International Nuclear Information System (INIS)

    Kumpulainen, H.; Uusheimo, K.

    1989-12-01

    Microfracturing of rock matrix around permeable fractures was studied experimentally from drill core samples around major fractures. The methods used were diffusion measurements using a 36 Cl-tracer and electrical resistivity measurements. Rock samples were from the Romuvaara investigation site, the granite specimen around a partially filled carbonate fracture (KR4/333 m) and gneiss specimen around a slickenside fracture (KR1/645 m). A consistent difference of one to two orders of magnitude in the levels of the methods with regard to the effective diffusion coefficients for Cl - -ion was found, the electrical resistivity measurement giving higher values. On the basis of the diffusion measurements the diffusion porosities could be calculated but these remained one to two orders of magnitude lower than that expected for granitic rocks using the water saturation method. A possible reason for these differences could have been the low, in some cases 0.004 M NaC1-concentration in the diffusion experiments vs. the 1 M NaCl-concentration used in the electrical resistivity measurements. Due to the small number of specimens and cross sectional areas of only 2 cm 2 , rock inhomogeneity effects were significant making the interpretation of the results somewhat troublesome. Porosities on fracture surfaces seemed to be higher than in the deeper, more intact rock matrix

  10. Anisotropy of strength and deformability of fractured rocks

    Directory of Open Access Journals (Sweden)

    Majid Noorian Bidgoli

    2014-04-01

    Full Text Available Anisotropy of the strength and deformation behaviors of fractured rock masses is a crucial issue for design and stability assessments of rock engineering structures, due mainly to the non-uniform and non-regular geometries of the fracture systems. However, no adequate efforts have been made to study this issue due to the current practical impossibility of laboratory tests with samples of large volumes containing many fractures, and the difficulty for controlling reliable initial and boundary conditions for large-scale in situ tests. Therefore, a reliable numerical predicting approach for evaluating anisotropy of fractured rock masses is needed. The objective of this study is to systematically investigate anisotropy of strength and deformability of fractured rocks, which has not been conducted in the past, using a numerical modeling method. A series of realistic two-dimensional (2D discrete fracture network (DFN models were established based on site investigation data, which were then loaded in different directions, using the code UDEC of discrete element method (DEM, with changing confining pressures. Numerical results show that strength envelopes and elastic deformability parameters of tested numerical models are significantly anisotropic, and vary with changing axial loading and confining pressures. The results indicate that for design and safety assessments of rock engineering projects, the directional variations of strength and deformability of the fractured rock mass concerned must be treated properly with respect to the directions of in situ stresses. Traditional practice for simply positioning axial orientation of tunnels in association with principal stress directions only may not be adequate for safety requirements. Outstanding issues of the present study and suggestions for future study are also presented.

  11. Transient diffusion from a waste solid into fractured porous rock

    International Nuclear Information System (INIS)

    Ahn, J.; Chambre, P.L.; Pigford, T.H.

    1988-01-01

    Previous analytical studies of the advective transport of dissolved contaminants through fractured rock have emphasized the effect of molecular diffusion in the rock matrix in affecting the space-time-dependent concentration of the contaminant as it moves along the fracture. Matrix diffusion only in the direction normal to the fracture surface was assumed. Contaminant sources were constant-concentration surfaces of width equal to the fracture aperture and of finite or infinite extent in the transverse direction. Such studies illustrate the far-field transport features of fractured media. To predict the time-dependent mass transfer from a long waste cylinder surrounded by porous rock and intersected by a fracture, the present study includes diffusion from the waste surface directly into porous rock, as well as the more realistic geometry. Here the authors present numerical results from Chambre's analytical solution for the time-dependent mass transfer from the cylinder for the low-flow conditions wherein near-field mass transfer is expected to be controlled by molecular diffusion

  12. Evaluation of scale effects on hydraulic characteristics of fractured rock using fracture network model

    International Nuclear Information System (INIS)

    Ijiri, Yuji; Sawada, Atsushi; Uchida, Masahiro; Ishiguro, Katsuhiko; Umeki, Hiroyuki; Sakamoto, Kazuhiko; Ohnishi, Yuzo

    2001-01-01

    It is important to take into account scale effects on fracture geometry if the modeling scale is much larger than the in-situ observation scale. The scale effect on fracture trace length, which is the most scale dependent parameter, is investigated using fracture maps obtained at various scales in tunnel and dam sites. We found that the distribution of fracture trace length follows negative power law distribution in regardless of locations and rock types. The hydraulic characteristics of fractured rock is also investigated by numerical analysis of discrete fracture network (DFN) model where power law distribution of fracture radius is adopted. We found that as the exponent of power law distribution become larger, the hydraulic conductivity of DFN model increases and the travel time in DFN model decreases. (author)

  13. Permeability and Dispersion Coefficients in Rocks with Fracture Network - 12140

    Energy Technology Data Exchange (ETDEWEB)

    Lee, C.K.; Htway, M.Z. [Handong Global University, 3 Namsong-ri, Heunghae-eub, Buk-gu, Pohang, Kyungbuk, 791-708 (Korea, Republic of); Yim, S.P. [Korea Atomic Energy Research Institute, P.O.Box 150, Yusong, Daejon, 305-600 (Korea, Republic of)

    2012-07-01

    Fluid flow and solute transport are considered for a rock medium with a fracture network with regard to the effective permeability and the dispersion coefficients. To investigate the effects of individual fractures a three-fracture system is chosen in which two are parallel and the third one connects the two at different angles. Specifically the micro-cell boundary-value problems(defined through multiple scale analysis) are solved numerically by using finite elements to calculate the permeability and dispersion coefficients. It is shown that the permeability depends significantly on the pattern of the fracture distribution and the dispersion coefficient is influenced by both the externally imposed pressure gradient (which also reflects the flow field) and the direction of the gradient of solute concentration on the macro-scale. From the calculations of the permeability and dispersion coefficients for solute in a rock medium with a fracture network the following conclusions are drawn. 1. The permeability of fractured medium depends on the primary orientation of the fracture network and is influenced by the connecting fractures in the medium. 2. The cross permeability, e.g., permeability in the direction normal to the direction of the external pressure gradient is rather insensitive to the orientation of the fracture network. 3. Calculation of permeability is most efficiently achieved with optimal discretization across individual fractures and is rather insensitive to the discretization along the fracture.. 4. The longitudinal dispersion coefficient Dxx of a fractured medium depends on both the macro-scale concentration gradient and the direction of the flow (pressure gradient). Hence both features must be considered when investigating solute transport in a fractured medium. (authors)

  14. The Behaviour of Fracture Growth in Sedimentary Rocks: A Numerical Study Based on Hydraulic Fracturing Processes

    Directory of Open Access Journals (Sweden)

    Lianchong Li

    2016-03-01

    Full Text Available To capture the hydraulic fractures in heterogeneous and layered rocks, a numerical code that can consider the coupled effects of fluid flow, damage, and stress field in rocks is presented. Based on the characteristics of a typical thin and inter-bedded sedimentary reservoir, China, a series of simulations on the hydraulic fracturing are performed. In the simulations, three points, i.e., (1 confining stresses, representing the effect of in situ stresses, (2 strength of the interfaces, and (3 material properties of the layers on either side of the interface, are crucial in fracturing across interfaces between two adjacent rock layers. Numerical results show that the hydrofracture propagation within a layered sequence of sedimentary rocks is controlled by changing in situ stresses, interface properties, and lithologies. The path of the hydraulic fracture is characterized by numerous deflections, branchings, and terminations. Four types of potential interaction, i.e., penetration, arrest, T-shaped branching, and offset, between a hydrofracture and an interface within the layered rocks are formed. Discontinuous composite fracture segments resulting from out-of-plane growth of fractures provide a less permeable path for fluids, gas, and oil than a continuous planar composite fracture, which are one of the sources of the high treating pressures and reduced fracture volume.

  15. Prediction of Fracture Behavior in Rock and Rock-like Materials Using Discrete Element Models

    Science.gov (United States)

    Katsaga, T.; Young, P.

    2009-05-01

    The study of fracture initiation and propagation in heterogeneous materials such as rock and rock-like materials are of principal interest in the field of rock mechanics and rock engineering. It is crucial to study and investigate failure prediction and safety measures in civil and mining structures. Our work offers a practical approach to predict fracture behaviour using discrete element models. In this approach, the microstructures of materials are presented through the combination of clusters of bonded particles with different inter-cluster particle and bond properties, and intra-cluster bond properties. The geometry of clusters is transferred from information available from thin sections, computed tomography (CT) images and other visual presentation of the modeled material using customized AutoCAD built-in dialog- based Visual Basic Application. Exact microstructures of the tested sample, including fractures, faults, inclusions and void spaces can be duplicated in the discrete element models. Although the microstructural fabrics of rocks and rock-like structures may have different scale, fracture formation and propagation through these materials are alike and will follow similar mechanics. Synthetic material provides an excellent condition for validating the modelling approaches, as fracture behaviours are known with the well-defined composite's properties. Calibration of the macro-properties of matrix material and inclusions (aggregates), were followed with the overall mechanical material responses calibration by adjusting the interfacial properties. The discrete element model predicted similar fracture propagation features and path as that of the real sample material. The path of the fractures and matrix-inclusion interaction was compared using computed tomography images. Initiation and fracture formation in the model and real material were compared using Acoustic Emission data. Analysing the temporal and spatial evolution of AE events, collected during the

  16. Mixing induced reactive transport in fractured crystalline rocks

    International Nuclear Information System (INIS)

    Martinez-Landa, Lurdes; Carrera, Jesus; Dentz, Marco; Fernàndez-Garcia, Daniel; Nardí, Albert; Saaltink, Maarten W.

    2012-01-01

    In this paper the solute retention properties of crystalline fractured rocks due to mixing-induced geochemical reactions are studied. While fractured media exhibit paths of fast flow and transport and thus short residence times for conservative solutes, at the same time they promote mixing and dilution due to strong heterogeneity, which leads to sharp concentration contrasts. Enhanced mixing and dilution have a double effect that favors crystalline fractured media as a possible host medium for nuclear waste disposal. Firstly, peak radionuclide concentrations are attenuated and, secondly, mixing-induced precipitation reactions are enhanced significantly, which leads to radionuclide immobilization. An integrated framework is presented for the effective modeling of these flow, transport and reaction phenomena, and the interaction between them. In a simple case study, the enhanced dilution and precipitation potential of fractured crystalline rocks are systematically studied and quantified and contrasted it to retention and attenuation in an equivalent homogeneous formation.

  17. Acoustic Resonance Characteristics of Rock and Concrete Containing Fractures

    Energy Technology Data Exchange (ETDEWEB)

    Nakagawa, Seiji [Univ. of California, Berkeley, CA (United States)

    1998-08-01

    In recent years, acoustic resonance has drawn great attention as a quantitative tool for characterizing properties of materials and detecting defects in both engineering and geological materials. In quasi-brittle materials such as rock and concrete, inherent fractures have a significant influence on their mechanical and hydraulic properties. Most of these fractures are partially open, providing internal boundaries that are visible to propagating seismic waves. Acoustic resonance occurs as a result of constructive and destructive interferences of propagating waves. Therefore the geometrical and mechanical properties of the fracture are also interrogated by the acoustic resonance characteristics of materials. The objective of this dissertation is to understand the acoustic resonance characteristics of fractured rock and concrete.

  18. Drill-back studies examine fractured, heated rock

    International Nuclear Information System (INIS)

    Wollenberg, H.A.; Flexser, S.; Myer, L.R.

    1990-01-01

    To investigate the effects of heating on the mineralogical, geochemical, and mechanical properties of rock by high-level radioactive waste, cores are being examined from holes penetrating locations where electric heaters simulated the presence of a waste canister, and from holes penetration natural hydrothermal systems. Results to date indicate the localized mobility and deposition of uranium in an open fracture in heated granitic rock, the mobility of U in a breccia zone in an active hydrothermal system in tuff, and the presence of U in relatively high concentration in fracture-lining material in tuff. Mechanical -- property studies indicate that differences in compressional- and shear-wave parameters between heated and less heated rock can be attributed to differences in the density of microcracks. Emphasis has shifted from initial studies of granitic rock at Stripa, Sweden to current investigations of welded tuff at the Nevada Test Site. 7 refs., 8 figs

  19. XFEM modeling of hydraulic fracture in porous rocks with natural fractures

    Science.gov (United States)

    Wang, Tao; Liu, ZhanLi; Zeng, QingLei; Gao, Yue; Zhuang, Zhuo

    2017-08-01

    Hydraulic fracture (HF) in porous rocks is a complex multi-physics coupling process which involves fluid flow, diffusion and solid deformation. In this paper, the extended finite element method (XFEM) coupling with Biot theory is developed to study the HF in permeable rocks with natural fractures (NFs). In the recent XFEM based computational HF models, the fluid flow in fractures and interstitials of the porous media are mostly solved separately, which brings difficulties in dealing with complex fracture morphology. In our new model the fluid flow is solved in a unified framework by considering the fractures as a kind of special porous media and introducing Poiseuille-type flow inside them instead of Darcy-type flow. The most advantage is that it is very convenient to deal with fluid flow inside the complex fracture network, which is important in shale gas extraction. The weak formulation for the new coupled model is derived based on virtual work principle, which includes the XFEM formulation for multiple fractures and fractures intersection in porous media and finite element formulation for the unified fluid flow. Then the plane strain Kristianovic-Geertsma-de Klerk (KGD) model and the fluid flow inside the fracture network are simulated to validate the accuracy and applicability of this method. The numerical results show that large injection rate, low rock permeability and isotropic in-situ stresses tend to lead to a more uniform and productive fracture network.

  20. Ozone generation by rock fracture: Earthquake early warning?

    Energy Technology Data Exchange (ETDEWEB)

    Baragiola, Raul A.; Dukes, Catherine A.; Hedges, Dawn [Engineering Physics, University of Virginia, Charlottesville, Virginia 22904 (United States)

    2011-11-14

    We report the production of up to 10 ppm ozone during crushing and grinding of typical terrestrial crust rocks in air, O{sub 2} and CO{sub 2} at atmospheric pressure, but not in helium or nitrogen. Ozone is formed by exoelectrons emitted by high electric fields, resulting from charge separation during fracture. The results suggest that ground level ozone produced by rock fracture, besides its potential health hazard, can be used for early warning in earthquakes and other catastrophes, such as landslides or land shifts in excavation tunnels and underground mines.

  1. Assessing geotechnical centrifuge modelling in addressing variably saturated flow in soil and fractured rock.

    Science.gov (United States)

    Jones, Brendon R; Brouwers, Luke B; Van Tonder, Warren D; Dippenaar, Matthys A

    2017-05-01

    The vadose zone typically comprises soil underlain by fractured rock. Often, surface water and groundwater parameters are readily available, but variably saturated flow through soil and rock are oversimplified or estimated as input for hydrological models. In this paper, a series of geotechnical centrifuge experiments are conducted to contribute to the knowledge gaps in: (i) variably saturated flow and dispersion in soil and (ii) variably saturated flow in discrete vertical and horizontal fractures. Findings from the research show that the hydraulic gradient, and not the hydraulic conductivity, is scaled for seepage flow in the geotechnical centrifuge. Furthermore, geotechnical centrifuge modelling has been proven as a viable experimental tool for the modelling of hydrodynamic dispersion as well as the replication of similar flow mechanisms for unsaturated fracture flow, as previously observed in literature. Despite the imminent challenges of modelling variable saturation in the vadose zone, the geotechnical centrifuge offers a powerful experimental tool to physically model and observe variably saturated flow. This can be used to give valuable insight into mechanisms associated with solid-fluid interaction problems under these conditions. Findings from future research can be used to validate current numerical modelling techniques and address the subsequent influence on aquifer recharge and vulnerability, contaminant transport, waste disposal, dam construction, slope stability and seepage into subsurface excavations.

  2. Gas Transport through Fractured Rock near the U20az Borehole, Pahute Mesa, Nevada.

    Science.gov (United States)

    Rockhold, M.; Lowrey, J. D.; Kirkham, R.; Olsen, K.; Waichler, S.; White, M. D.; Wurstner White, S.

    2017-12-01

    Field experiments were performed in 2012-13 and 2016-17 at the U-20az testbed at the Nevada National Security Site to develop and evaluate capabilities for monitoring and modeling noble gas transport associated with underground nuclear explosions (UNE). Experiments were performed by injecting both chemical (CF2BR2, SF6) and radioactive (37Ar, 127Xe) gas species into the deep subsurface at this legacy UNE site and monitoring the breakthrough of the gases at different locations on or near the ground surface. Gas pressures were also monitored in both the chimney and at ground surface. Field experiments were modeled using the parallel, non-isothermal, two-phase flow and transport simulator, STOMP-GT. A site conceptual-numerical model was developed from a geologic framework model, and using a dual-porosity/permeability model for the constitutive relative permeability-saturation-capillary pressure relations of the fractured rock units. Comparisons of observed and simulated gas species concentrations show that diffusion is a highly effective transport mechanism under ambient conditions in the water-unsaturated fractured rock. Over-pressurization of the cavity during one of the field campaigns, and barometric pressure fluctuations are shown to result in enhanced gas transport by advection through fractures.

  3. Simulation of Anisotropic Rock Damage for Geologic Fracturing

    Science.gov (United States)

    Busetti, S.; Xu, H.; Arson, C. F.

    2014-12-01

    A continuum damage model for differential stress-induced anisotropic crack formation and stiffness degradation is used to study geologic fracturing in rocks. The finite element-based model solves for deformation in the quasi-linear elastic domain and determines the six component damage tensor at each deformation increment. The model permits an isotropic or anisotropic intact or pre-damaged reference state, and the elasticity tensor evolves depending on the stress path. The damage variable, similar to Oda's fabric tensor, grows when the surface energy dissipated by three-dimensional opened cracks exceeds a threshold defined at the appropriate scale of the representative elementary volume (REV). At the laboratory or wellbore scale (1000m) scales the damaged REV reflects early natural fracturing (background or tectonic fracturing) or shear strain localization (fault process zone, fault-tip damage, etc.). The numerical model was recently benchmarked against triaxial stress-strain data from laboratory rock mechanics tests. However, the utility of the model to predict geologic fabric such as natural fracturing in hydrocarbon reservoirs was not fully explored. To test the ability of the model to predict geological fracturing, finite element simulations (Abaqus) of common geologic scenarios with known fracture patterns (borehole pressurization, folding, faulting) are simulated and the modeled damage tensor is compared against physical fracture observations. Simulated damage anisotropy is similar to that derived using fractured rock-mass upscaling techniques for pre-determined fracture patterns. This suggests that if model parameters are constrained with local data (e.g., lab, wellbore, or reservoir domain), forward modeling could be used to predict mechanical fabric at the relevant REV scale. This reference fabric also can be used as the starting material property to pre-condition subsequent deformation or fluid flow. Continuing efforts are to expand the present damage

  4. Underground nuclear explosion effects in granite rock fracturing

    International Nuclear Information System (INIS)

    Derlich, S.

    1970-01-01

    On the Saharan nuclear test site in Hoggar granite, mechanical properties of the altered zones were studied by in situ and laboratory measurements. In situ methods of study are drillings, television, geophysical and permeability measurements. Fracturing is one of the most important nuclear explosion effects. Several altered zones were identified. There are: crushed zone, fractured zone and stressed zone. Collapse of crushed and fractured zone formed the chimney. The extent of each zone can be expressed in terms of yield and of characteristic parameters. Such results are of main interest for industrial uses of underground nuclear explosives in hard rock. (author)

  5. Underground nuclear explosion effects in granite rock fracturing

    Energy Technology Data Exchange (ETDEWEB)

    Derlich, S [Commissariat a l' Energie Atomique, Centre d' Etude de Bruyeres-le-Chatel (France)

    1970-05-01

    On the Saharan nuclear test site in Hoggar granite, mechanical properties of the altered zones were studied by in situ and laboratory measurements. In situ methods of study are drillings, television, geophysical and permeability measurements. Fracturing is one of the most important nuclear explosion effects. Several altered zones were identified. There are: crushed zone, fractured zone and stressed zone. Collapse of crushed and fractured zone formed the chimney. The extent of each zone can be expressed in terms of yield and of characteristic parameters. Such results are of main interest for industrial uses of underground nuclear explosives in hard rock. (author)

  6. Water flow and solute transport through fractured rock

    International Nuclear Information System (INIS)

    Bolt, J.E.; Bourke, P.J.; Pascoe, D.M.; Watkins, V.M.B.; Kingdon, R.D.

    1990-09-01

    In densely fractured slate at the Nirex research site in Cornwall, the positions, orientations and hydraulic conductivities of the 380 fractures intersecting a drill hole between 9 and 50 m depth have been individually measured. These data have been used: to determine the dimensions of statistically representative volumes of the network of fractures and to predict, using discrete flow path modelling and the NAPSAC code, the total flows into the fractures when large numbers are simultaneously pressurised along various lengths of the hole. Corresponding measurements, which validated the NAPSAC code to factor of two accuracy for the Cornish site, are reported. Possibilities accounting for this factor are noted for experimental investigation, and continuing, more extensive, inter hole flow and transport measurements are outlined. The application of this experimental and theoretical approach for calculating radionuclide transport in less densely fractured rock suitable for waste disposal is discussed. (Author)

  7. Water flow and solute transport through fractured rock

    International Nuclear Information System (INIS)

    Bourke, P.J.; Kingdon, R.D.; Bolt, J.E.; Pascoe, D.M.; Watkins, V.M.B.

    1991-01-01

    In densely fractured slate at the Nirex research site in Cornwall, the positions, orientations and hydraulic conductivities of the 380 fractures intersecting a drill hole between 9 and 50 m depths have been individually measured. These data have been used: - to determine the dimensions of statistically representative volumes of the sheetwork of fractures; - to predict; using discrete flowpath modelling and the NAPSAC code; the total flows into the fractures when large numbers are simultaneously pressurised along various lengths of the hole; Corresponding measurements, which proved the modelling and validated the code to factor of two accuracy, are reported. Possibilities accounting for this factor are noted for experimental investigation, and continuing, more extensive inter-hole flow and transport measurements are outlined. The application of this experimental and theoretical approach for calculating radionuclide transport in less densely fractured rock suitable for waste disposal is discussed. 7 figs., 9 refs

  8. Small-scale electrical resistivity tomography of wet fractured rocks.

    Science.gov (United States)

    LaBrecque, Douglas J; Sharpe, Roger; Wood, Thomas; Heath, Gail

    2004-01-01

    This paper describes a series of experiments that tested the ability of the electrical resistivity tomography (ERT) method to locate correctly wet and dry fractures in a meso-scale model. The goal was to develop a method of monitoring the flow of water through a fractured rock matrix. The model was a four by six array of limestone blocks equipped with 28 stainless steel electrodes. Dry fractures were created by placing pieces of vinyl between one or more blocks. Wet fractures were created by injecting tap water into a joint between blocks. In electrical terms, the dry fractures are resistive and the wet fractures are conductive. The quantities measured by the ERT system are current and voltage around the outside edge of the model. The raw ERT data were translated to resistivity values inside the model using a three-dimensional Occam's inversion routine. This routine was one of the key components of ERT being tested. The model presented several challenges. First, the resistivity of both the blocks and the joints was highly variable. Second, the resistive targets introduced extreme changes the software could not precisely quantify. Third, the abrupt changes inherent in a fracture system were contrary to the smoothly varying changes expected by the Occam's inversion routine. Fourth, the response of the conductive fractures was small compared to the background variability. In general, ERT was able to locate correctly resistive fractures. Problems occurred, however, when the resistive fracture was near the edges of the model or when multiple fractures were close together. In particular, ERT tended to position the fracture closer to the model center than its true location. Conductive fractures yielded much smaller responses than the resistive case. A difference-inversion method was able to correctly locate these targets.

  9. Demonstration of a Fractured Rock Geophysical Toolbox (FRGT) for Characterization and Monitoring of DNAPL Biodegradation in Fractured Rock Aquifers

    Science.gov (United States)

    2015-09-29

    is characterized by dark gray slate or phyllite, alternating with thin layers of light gray siltstone or sandstone . Table 1 summarizes the primary...sedimentary rocks of the Newark Basin. Competent rocks are primarily mudstones and sandstones of the Lockatong and Stockton Formations. Fill, weathered silt... sandstone , and characterized by water bearing bedding plane fractures. An array of open boreholes in the source area that were drilled for the 2002

  10. Experimental assessment of the sealing effectiveness of rock fracture grouting

    International Nuclear Information System (INIS)

    Schaffer, A.; Daemen, J.J.K.

    1987-03-01

    The objective of this investigation is to determine the effectiveness of cement grouts as sealants of fractures in rock. Laboratory experiments have been conducted on seven 15-cm granite cubes containing saw cuts, three 23-cm diameter andesite cores containing induced tension cracks, and one 15-cm diameter marble core containing a natural fracture. Prior to grouting, the hydraulic conductivity of the fractures is determined under a range of normal stresses, applied in loading and unloading cycles, from 0 to 14 MPa (2000 psi). Grout is injected through an axial borehole, at a pressure of 1.2 to 8.3 MPa (180 to 1200 psi), pressure selected to provide a likely groutable fracture aperture, while the fracture is stressed at a constant normal stress. The fracture permeability is measured after grouting. Flow tests on the ungrouted samples confirm the inverse relation between normal stress and fracture permeability. The equivalent aperture determined by these tests is a reliable indicator of groutability. Postgrouting permeability measurements as performed here, and frequently in practice, can be misleading, since incomplete grouting of fractures can result in major apparent reductions in permeability. The apparent permeability reduction is caused by grouting of a small area of a highly preferential flowpath directly adjacent to the hole used for grouting and for permeability testing. Experimental results confirm claims in the literature that ordinary portland cement inadequately penetrates fine fractures

  11. Characterization of the fracturation of rock masses for determining flow

    International Nuclear Information System (INIS)

    Derlich, S.

    1984-02-01

    Flow in a rock mass is the consequence of the permeability of the rock, which can be roughly separated into matrix permeability and fissure permeability. In crystalline rocks fissure permeability is dominant, especially where the rocks are extensively fractured. It is thus essential, by means of studies either at the surface or underground, to characterize the volume fracturation in the mass considered. The purpose of this paper is to illustrate the methodology for analysing fracturation at a site by the studies performed on the granite mass of Auriat in the French Massif Central. A number of geology laboratories have participated in this study and a broad spectrum of observations has been made which can be used for determining the various stages of a study with a view to selection of a site, the advantages and limitations of each method or study plan and additional methods which need to be used for gaining as complete a picture as possible of the fracturation. A brief examination of the results obtained at Auriat enables the relative advantages of using these various methods at a particular site to be compared

  12. Demonstration and Validation of a Fractured Rock Passive Flux Meter

    Science.gov (United States)

    2015-04-01

    attenuation, and enhanced biodegradation as competitive remediation solutions to chlorinated ethene-contaminated fractured rock. The criteria and...located outside, then some form of weatherproofing for the gauges will be necessary. As a temporary measure, heavy-duty polyethylene bags , secured

  13. An overview of geophysical technologies appropriate for characterization and monitoring at fractured-rock sites

    Science.gov (United States)

    Geophysical methods are used increasingly for characterization and monitoring at remediation sites in fractured-rock aquifers. The complex heterogeneity of fractured rock poses enormous challenges to groundwater remediation professionals, and new methods are needed to cost-effect...

  14. Statistical fracture mechanics approach to the strength of brittle rock

    International Nuclear Information System (INIS)

    Ratigan, J.L.

    1981-06-01

    Statistical fracture mechanics concepts used in the past for rock are critically reviewed and modifications are proposed which are warranted by (1) increased understanding of fracture provided by modern fracture mechanics and (2) laboratory test data both from the literature and from this research. Over 600 direct and indirect tension tests have been performed on three different rock types; Stripa Granite, Sierra White Granite and Carrara Marble. In several instances assumptions which are common in the literature were found to be invalid. A three parameter statistical fracture mechanics model with Mode I critical strain energy release rate as the variant is presented. Methodologies for evaluating the parameters in this model as well as the more commonly employed two parameter models are discussed. The experimental results and analysis of this research indicate that surfacially distributed flaws, rather than volumetrically distributed flaws are responsible for rupture in many testing situations. For several of the rock types tested, anisotropy (both in apparent tensile strength and size effect) precludes the use of contemporary statistical fracture mechanics models

  15. Implicit fracture modelling in FLAC3D: Assessing the behaviour of fractured shales, carbonates and other fractured rock types

    NARCIS (Netherlands)

    Osinga, S.; Pizzocolo, F.; Veer, E.F. van der; Heege, J.H. ter

    2016-01-01

    Fractured rocks play an important role in many types of petroleum and geo-energy operations. From fractured limestone reservoirs to unconventionals, understanding the geomechanical behaviour and the dynamically coupled (dual) permeability system is paramount for optimal development of these systems.

  16. A fractured rock geophysical toolbox method selection tool

    Science.gov (United States)

    Day-Lewis, F. D.; Johnson, C.D.; Slater, L.D.; Robinson, J.L.; Williams, J.H.; Boyden, C.L.; Werkema, D.D.; Lane, J.W.

    2016-01-01

    Geophysical technologies have the potential to improve site characterization and monitoring in fractured rock, but the appropriate and effective application of geophysics at a particular site strongly depends on project goals (e.g., identifying discrete fractures) and site characteristics (e.g., lithology). No method works at every site or for every goal. New approaches are needed to identify a set of geophysical methods appropriate to specific project goals and site conditions while considering budget constraints. To this end, we present the Excel-based Fractured-Rock Geophysical Toolbox Method Selection Tool (FRGT-MST). We envision the FRGT-MST (1) equipping remediation professionals with a tool to understand what is likely to be realistic and cost-effective when contracting geophysical services, and (2) reducing applications of geophysics with unrealistic objectives or where methods are likely to fail.

  17. Analytic solution of pseudocolloid migration in fractured rock

    International Nuclear Information System (INIS)

    Hwang, Y.; Pigford, T.H.; Lee, W.W.L.; Chambre, P.L.

    1989-06-01

    A form of colloid migration that can enhance or retard the migration of a dissolved contaminant in ground water is the sorption of the contaminant on the moving colloidal particulate to form pseudocolloids. In this paper we develop analytical solutions for the interactive migration of radioactive species dissolved in ground water and sorbed as pseudocolloids. The solute and pseudocolloids are assumed to undergo advection and dispersion in a one-dimensional flow field in planar fractures in porous rock. Interaction between pseudocolloid and dissolved species is described by equilibrium sorption. Sorbed species on the pseudocolloids undergo radioactive decay, and pseudocolloids can sorb on fracture surfaces and sediments. Filtration is neglected. The solute can decay and sorb on pseudocolloids, on the fracture surfaces, and on sediments and can diffuse into the porous rock matrix. 1 fig

  18. Thermodynamics of energy extraction from fractured hot dry rock

    Energy Technology Data Exchange (ETDEWEB)

    Lim, J S; Bejan, A [Duke Univ., Durham, NC (United States). Dept. of Mechanical Engineering and Materials Science; Kim, J H [Electric Power Research Inst., Palo Alto, CA (United States)

    1992-03-01

    It has been proposed to extract energy from the subterranean hot dry rock bed (HDR) by creating one or more narrow fractures in the rock and circulating cold water through the fractures. In time, the temperature of the rock region surrounding the crack drops under the influence of time-dependent conduction. This study presents the most basic thermodynamic aspects (first law and second law) of the HDR energy extraction process. It shows which parameters most influence the amount of useful energy (exergy) extracted from the HDR reservoir over a fixed time interval. For example, the water flow rate can be selected optimally in order to maximize the delivery of exergy over the lifetime of the HDR system. (author).

  19. Creep in the sparsely fractured rock between a disposal vault and a zone of highly fractured rock

    International Nuclear Information System (INIS)

    Wilkins, B.J.S.; Rigby, G.L.

    1993-08-01

    AECL Research is responsible for investigating the feasibility and safety of the disposal of Canada's nuclear fuel waste deep in the plutonic rock of the Canadian Shield. The excavation of the disposal vault, the installation of sealing systems and the heat generated by the fuel waste will all perturb the in situ stress state of the rock mass. This computer codes HOTROK, MCROC and MCDIRC are used to analyze the influence of these stress perturbations on the mechanical behaviour of the rock mass. Time-dependent microcracking of the rock mass will lead to creep around openings in the vault. The analysis specifically estimates the resulting creep strain in the sparsely fractured rock between the edge of the disposal vault and a postulated zone of highly fractured rock. The estimates are extremely conservative. The conclusion reached is that the rock mass more than 3 m beyond the edge of the vault will experience < 0.001 creep strain 100 000 years after the fuel waste is emplaced. (author). 10 refs., 4 tabs., 4 figs

  20. OBSERVATION AND ANALYSIS OF A PRONOUNCED PERMEABILITY AND POROSITY SCALE-EFFECT IN UNSATURATED FRACTURED TUFF

    Energy Technology Data Exchange (ETDEWEB)

    V. VESSELINOV; ET AL

    2001-01-01

    Over 270 single-hole (Guzman et al., 1996) and 44 cross-hole pneumatic injection tests (Illman et al., 1998; Illman, 1999) have been conducted at the Apache Leap Research Site (ALRS) near Superior, Arizona. They have shown that the pneumatic pressure behavior of fractured tuff at the site is amenable to analysis by methods which treat the rock as a continuum on scales ranging from meters to tens of meters, and that this continuum is representative primarily of interconnected fractures. Both the single-hole and cross-hole test results are free of skin effect. Single-hole tests have yielded estimates of air permeability at various locations throughout the tested rock volume, on a nominal support scale of about 1 m. The corresponding log permeability data exhibit spatial behavior characteristic of a random fractal and yield a kriged estimate of how these 1-m scale log permeabilities vary in three-dimensional space (Chen et al., 2000). Cross-hole tests have been analyzed by means of a three-dimensional inverse model (Vesselinov et al., 2000) in two ways: (a) by interpreting pressure records from individual borehole monitoring intervals, one at a time, while treating the rock as if it was spatially uniform; and (b) by using the inverse model to interpret pressure records from multiple tests and borehole monitoring intervals simultaneously, while treating the rock as a random fractal characterized by a power variogram. The first approach has yielded equivalent air permeabilities and air-filled porosities for a rock volume characterized by a length-scale of several tens of meters. Comparable results have been obtained by means of type-curves (Illman and Neuman, 2001). The second approach amounts to three-dimensional pneumatic tomography, or stochastic imaging, of the rock. It has yielded a high-resolution geostatistical estimate of how air permeability and air-filled porosity, defined over grid blocks having a length-scale of 1 m, vary throughout the modeled rock volume

  1. On conditions and parameters important to model sensitivity for unsaturated flow through layered, fractured tuff

    International Nuclear Information System (INIS)

    Prindle, R.W.; Hopkins, P.L.

    1990-10-01

    The Hydrologic Code Intercomparison Project (HYDROCOIN) was formed to evaluate hydrogeologic models and computer codes and their use in performance assessment for high-level radioactive-waste repositories. This report describes the results of a study for HYDROCOIN of model sensitivity for isothermal, unsaturated flow through layered, fractured tuffs. We investigated both the types of flow behavior that dominate the performance measures and the conditions and model parameters that control flow behavior. We also examined the effect of different conceptual models and modeling approaches on our understanding of system behavior. The analyses included single- and multiple-parameter variations about base cases in one-dimensional steady and transient flow and in two-dimensional steady flow. The flow behavior is complex even for the highly simplified and constrained system modeled here. The response of the performance measures is both nonlinear and nonmonotonic. System behavior is dominated by abrupt transitions from matrix to fracture flow and by lateral diversion of flow. The observed behaviors are strongly influenced by the imposed boundary conditions and model constraints. Applied flux plays a critical role in determining the flow type but interacts strongly with the composite-conductivity curves of individual hydrologic units and with the stratigraphy. One-dimensional modeling yields conservative estimates of distributions of groundwater travel time only under very limited conditions. This study demonstrates that it is wrong to equate the shortest possible water-travel path with the fastest path from the repository to the water table. 20 refs., 234 figs., 10 tabs

  2. Nanoparticles migration in fractured rocks and affects on contaminant migration

    Science.gov (United States)

    Missana, Tiziana; Garcia-Gutierrez, Miguel; Alonso, Ursula

    2014-05-01

    In previous studies, the transport behavior of artificial (gold and latex) and natural (smectite clay) colloids, within a planar fracture in crystalline rock, was analyzed. In order to better understand the effects of colloid size, shape and surface charge on nanoparticle migration and especially on filtration processes on natural rock surfaces, different clay colloids and oxide nanoparticles were selected and their transport studied as a function of the residence time. In all the cases, (a fraction of) the nanoparticles travelled in the fracture as fast as or faster than water (with a retardation factor, Rf ≤ 1) and the observed Rf, was related to the Taylor dispersion coefficient, accounting for colloid size, water velocity and fracture width. However, under most of the cases, in contrast to the behavior of a conservative tracer, colloids recovery was much lower than 100 %. Differences in recovery between different nanoparticles, under similar residence times, were analyzed. In order to evaluate the possible consequences, on contaminant migration, of the presence of nanoparticles in the system, transport tests were carried out with both colloids and sorbing radionuclides. The overall capacity for colloids of enhancing radionuclide migration in crystalline rock fractures is discussed. Acknowledgments: The research leading to these results received funding from EU FP7/2007-2011 grant agreement Nº 295487 (BELBAR, Bentonite Erosion: effects on the Long term performance of the engineered Barrier and Radionuclide Transport) and by the Spanish Government under the project NANOBAG (CTM2011-2797).

  3. Fracture Characterization in Reactive Fluid-Fractured Rock Systems Using Tracer Transport Data

    Science.gov (United States)

    Mukhopadhyay, S.

    2014-12-01

    Fractures, whether natural or engineered, exert significant controls over resource exploitation from contemporary energy sources including enhanced geothermal systems and unconventional oil and gas reserves. Consequently, fracture characterization, i.e., estimating the permeability, connectivity, and spacing of the fractures is of critical importance for determining the viability of any energy recovery program. While some progress has recently been made towards estimating these critical fracture parameters, significant uncertainties still remain. A review of tracer technology, which has a long history in fracture characterization, reveals that uncertainties exist in the estimated parameters not only because of paucity of scale-specific data but also because of knowledge gaps in the interpretation methods, particularly in interpretation of tracer data in reactive fluid-rock systems. We have recently demonstrated that the transient tracer evolution signatures in reactive fluid-rock systems are significantly different from those in non-reactive systems (Mukhopadhyay et al., 2013, 2014). For example, the tracer breakthrough curves in reactive fluid-fractured rock systems are expected to exhibit a long pseudo-state condition, during which tracer concentration does not change by any appreciable amount with passage of time. Such a pseudo-steady state condition is not observed in a non-reactive system. In this paper, we show that the presence of this pseudo-steady state condition in tracer breakthrough patterns in reactive fluid-rock systems can have important connotations for fracture characterization. We show that the time of onset of the pseudo-steady state condition and the value of tracer concentration in the pseudo-state condition can be used to reliably estimate fracture spacing and fracture-matrix interface areas.

  4. Research on fracture analysis, groundwater flow and sorption processes in fractured rocks

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Dae Ha [Korea Institute of Geology Mining and Materials, Taejon (Korea)

    1998-12-01

    Due to increasing demand for numerous industrial facilities including nuclear power plants and waste repositories, the feasibility of rocks masses as sites for the facilities has been a geological issue of concern. Rock masses, in general, comprises systems of fractures which can provide pathways for groundwater flow and may also affect the stability of engineered structures. such properties of fractures stimulate a synthetic study on (1) analyses of fracture systems, and (2) characterization of groundwater flow and sorption processes in fractured rocks to establish a preliminary model for assessing suitable sites for industrial facilities. The analyses of fracture systems cover (1) reconstruction of the Cenozoic tectonic movements and estimation of frequency indices for the Holocene tectonic movements, (2) determination of distributions and block movements of the Quaternary marine terraces, (3) investigation of lithologic and geotechnical nature of study area, and (4) examination of the Cenozoic volcanic activities and determination of age of the dike swarms. Using data obtained from above mentioned analyses along with data related to earthquakes and active faults, probabilistic approach is performed to determine various potential hazards which may result from the Quaternary or the Holocene tectonic movements. In addition, stepwise and careful integration of various data obtained from field works and laboratory experiments are carried out to analyze groundwater flow in fractures rocks as follows; (1) investigation of geological feature of the site, (2) identification and characterization of fracture systems using core and televiewer logs, (3) determination of conductive fractures using electrical conductivity, temperature, and flow logs, (4) identification of hydraulic connections between fractures using televiewer logs with tracer tests within specific zones. The results obtained from these processes allow a qualitative interpretation of groundwater flow patterns

  5. Hydrogeologic framework of fractured sedimentary rock, Newark Basin, New Jersey

    Science.gov (United States)

    Lacombe, Pierre J.; Burton, William C.

    2010-01-01

    The hydrogeologic framework of fractured sedimentary bedrock at the former Naval Air Warfare Center (NAWC), Trenton, New Jersey, a trichloroethylene (TCE)-contaminated site in the Newark Basin, is developed using an understanding of the geologic history of the strata, gamma-ray logs, and rock cores. NAWC is the newest field research site established as part of the U.S. Geological Survey Toxic Substances Hydrology Program, Department of Defense (DoD) Strategic Environmental Research and Development Program, and DoD Environmental Security Technology Certification Program to investigate contaminant remediation in fractured rock. Sedimentary bedrock at the NAWC research site comprises the Skunk Hollow, Byram, and Ewing Creek Members of the Lockatong Formation and Raven Rock Member of the Stockton Formation. Muds of the Lockatong Formation that were deposited in Van Houten cycles during the Triassic have lithified to form the bedrock that is typical of much of the Newark Basin. Four lithotypes formed from the sediments include black, carbon-rich laminated mudstone, dark-gray laminated mudstone, light-gray massive mudstone, and red massive mudstone. Diagenesis, tectonic compression, off-loading, and weathering have altered the rocks to give some strata greater hydraulic conductivity than other strata. Each stratum in the Lockatong Formation is 0.3 to 8 m thick, strikes N65 degrees E, and dips 25 degrees to 70 degrees NW. The black, carbon-rich laminated mudstone tends to fracture easily, has a relatively high hydraulic conductivity and is associated with high natural gamma-ray count rates. The dark-gray laminated mudstone is less fractured and has a lower hydraulic conductivity than the black carbon-rich laminated mudstone. The light-gray and the red massive mudstones are highly indurated and tend to have the least fractures and a low hydraulic conductivity. The differences in gamma-ray count rates for different mudstones allow gamma-ray logs to be used to correlate and

  6. Effect of Random Natural Fractures on Hydraulic Fracture Propagation Geometry in Fractured Carbonate Rocks

    Science.gov (United States)

    Liu, Zhiyuan; Wang, Shijie; Zhao, Haiyang; Wang, Lei; Li, Wei; Geng, Yudi; Tao, Shan; Zhang, Guangqing; Chen, Mian

    2018-02-01

    Natural fractures have a significant influence on the propagation geometry of hydraulic fractures in fractured reservoirs. True triaxial volumetric fracturing experiments, in which random natural fractures are created by placing cement blocks of different dimensions in a cuboid mold and filling the mold with additional cement to create the final test specimen, were used to study the factors that influence the hydraulic fracture propagation geometry. These factors include the presence of natural fractures around the wellbore, the dimension and volumetric density of random natural fractures and the horizontal differential stress. The results show that volumetric fractures preferentially formed when natural fractures occurred around the wellbore, the natural fractures are medium to long and have a volumetric density of 6-9%, and the stress difference is less than 11 MPa. The volumetric fracture geometries are mainly major multi-branch fractures with fracture networks or major multi-branch fractures (2-4 fractures). The angles between the major fractures and the maximum horizontal in situ stress are 30°-45°, and fracture networks are located at the intersections of major multi-branch fractures. Short natural fractures rarely led to the formation of fracture networks. Thus, the interaction between hydraulic fractures and short natural fractures has little engineering significance. The conclusions are important for field applications and for gaining a deeper understanding of the formation process of volumetric fractures.

  7. Bioremediation in Fractured Rock: 2. Mobilization of Chloroethene Compounds from the Rock Matrix.

    Science.gov (United States)

    Shapiro, Allen M; Tiedeman, Claire R; Imbrigiotta, Thomas E; Goode, Daniel J; Hsieh, Paul A; Lacombe, Pierre J; DeFlaun, Mary F; Drew, Scott R; Curtis, Gary P

    2018-03-01

    A mass balance is formulated to evaluate the mobilization of chlorinated ethene compounds (CE) from the rock matrix of a fractured mudstone aquifer under pre- and postbioremediation conditions. The analysis relies on a sparse number of monitoring locations and is constrained by a detailed description of the groundwater flow regime. Groundwater flow modeling developed under the site characterization identified groundwater fluxes to formulate the CE mass balance in the rock volume exposed to the injected remediation amendments. Differences in the CE fluxes into and out of the rock volume identify the total CE mobilized from diffusion, desorption, and nonaqueous phase liquid dissolution under pre- and postinjection conditions. The initial CE mass in the rock matrix prior to remediation is estimated using analyses of CE in rock core. The CE mass mobilized per year under preinjection conditions is small relative to the total CE mass in the rock, indicating that current pump-and-treat and natural attenuation conditions are likely to require hundreds of years to achieve groundwater concentrations that meet regulatory guidelines. The postinjection CE mobilization rate increased by approximately an order of magnitude over the 5 years of monitoring after the amendment injection. This rate is likely to decrease and additional remediation applications over several decades would still be needed to reduce CE mass in the rock matrix to levels where groundwater concentrations in fractures achieve regulatory standards. © 2017, National Ground Water Association.

  8. Bioremediation in fractured rock: 2. Mobilization of chloroethene compounds from the rock matrix

    Science.gov (United States)

    Shapiro, Allen M.; Tiedeman, Claire; Imbrigiotta, Thomas; Goode, Daniel J.; Hsieh, Paul A.; Lacombe, Pierre; DeFlaun, Mary F.; Drew, Scott R.; Curtis, Gary P.

    2018-01-01

    A mass balance is formulated to evaluate the mobilization of chlorinated ethene compounds (CE) from the rock matrix of a fractured mudstone aquifer under pre- and postbioremediation conditions. The analysis relies on a sparse number of monitoring locations and is constrained by a detailed description of the groundwater flow regime. Groundwater flow modeling developed under the site characterization identified groundwater fluxes to formulate the CE mass balance in the rock volume exposed to the injected remediation amendments. Differences in the CE fluxes into and out of the rock volume identify the total CE mobilized from diffusion, desorption, and nonaqueous phase liquid dissolution under pre- and postinjection conditions. The initial CE mass in the rock matrix prior to remediation is estimated using analyses of CE in rock core. The CE mass mobilized per year under preinjection conditions is small relative to the total CE mass in the rock, indicating that current pump-and-treat and natural attenuation conditions are likely to require hundreds of years to achieve groundwater concentrations that meet regulatory guidelines. The postinjection CE mobilization rate increased by approximately an order of magnitude over the 5 years of monitoring after the amendment injection. This rate is likely to decrease and additional remediation applications over several decades would still be needed to reduce CE mass in the rock matrix to levels where groundwater concentrations in fractures achieve regulatory standards.

  9. Groundwater flow and sorption processes in fractured rocks (I)

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Won Young; Woo, Nam Chul; Yum, Byoung Woo; Choi, Young Sub; Chae, Byoung Kon; Kim, Jung Yul; Kim, Yoo Sung; Hyun, Hye Ja; Lee, Kil Yong; Lee, Seung Gu; Youn, Youn Yul; Choon, Sang Ki [Korea Institute of Geology Mining and Materials, Taejon (Korea, Republic of)

    1996-12-01

    This study is objected to characterize groundwater flow and sorption processes of the contaminants (ground-water solutes) along the fractured crystalline rocks in Korea. Considering that crystalline rock mass is an essential condition for using underground space cannot be overemphasized the significance of the characterizing fractured crystalline rocks. the behavior of the groundwater contaminants is studied in related to the subsurface structure, and eventually a quantitative technique will be developed to evaluate the impacts of the contaminants on the subsurface environments. The study has been carried at the Samkwang mine area in the Chung-Nam Province. The site has Pre-Cambrian crystalline gneiss as a bedrock and the groundwater flow system through the bedrock fractures seemed to be understandable with the study on the subsurface geologic structure through the mining tunnels. Borehole tests included core logging, televiewer logging, constant pressure fixed interval length tests and tracer tests. The results is summarized as follows; 1) To determine the hydraulic parameters of the fractured rock, the transient flow analysis produce better results than the steady - state flow analysis. 2) Based on the relationship between fracture distribution and transmissivities measured, the shallow part of the system could be considered as a porous and continuous medium due to the well developed fractures and weathering. However, the deeper part shows flow characteristics of the fracture dominant system, satisfying the assumptions of the Cubic law. 3) Transmissivities from the FIL test were averaged to be 6.12 x 10{sup -7}{sub m}{sup 2}{sub /s}. 4) Tracer tests result indicates groundwater flow in the study area is controlled by the connection, extension and geometry of fractures in the bedrock. 5) Hydraulic conductivity of the tracer-test interval was in maximum of 7.2 x 10{sup -6}{sub m/sec}, and the effective porosity of 1.8 %. 6) Composition of the groundwater varies

  10. A stratified percolation model for saturated and unsaturated flow through natural fractures

    International Nuclear Information System (INIS)

    Pyrak-Nolte, L.J.

    1990-01-01

    The geometry of the asperities of contact between the two surfaces of a fracture and of the adjacent void spaces determines fluid flow through a fracture and the mechanical deformation across a fracture. Heuristically we have developed a stratified continuum percolation model to describe this geometry based on a fractal construction that includes scale invariance and correlation of void apertures. Deformation under stress is analyzed using conservation of rock volume to correct for asperity interpenetration. Single phase flow is analyzed using a critical path along which the principal resistance is a result of laminar flow across the critical neck in this path. Results show that flow decreases with apparent aperture raised to a variable power greater than cubic, as is observed in flow experiments on natural fractures. For two phases, flow of the non-wetting phase is likewise governed by the critical neck along the critical path of largest aperture but flow of the wetting phase is governed by tortuosity. 17 refs., 10 figs

  11. Fracture and Healing of Rock Salt Related to Salt Caverns

    International Nuclear Information System (INIS)

    Chan, K.S.; Fossum, A.F.; Munson, D.E.

    1999-01-01

    In recent years, serious investigations of potential extension of the useful life of older caverns or of the use of abandoned caverns for waste disposal have been of interest to the technical community. All of the potential applications depend upon understanding the reamer in which older caverns and sealing systems can fail. Such an understanding will require a more detailed knowledge of the fracture of salt than has been necessary to date. Fortunately, the knowledge of the fracture and healing of salt has made significant advances in the last decade, and is in a position to yield meaningful insights to older cavern behavior. In particular, micromechanical mechanisms of fracture and the concept of a fracture mechanism map have been essential guides, as has the utilization of continuum damage mechanics. The Multimechanism Deformation Coupled Fracture (MDCF) model, which is summarized extensively in this work was developed specifically to treat both the creep and fracture of salt, and was later extended to incorporate the fracture healing process known to occur in rock salt. Fracture in salt is based on the formation and evolution of microfractures, which may take the form of wing tip cracks, either in the body or the boundary of the grain. This type of crack deforms under shear to produce a strain, and furthermore, the opening of the wing cracks produce volume strain or dilatancy. In the presence of a confining pressure, microcrack formation may be suppressed, as is often the case for triaxial compression tests or natural underground stress situations. However, if the confining pressure is insufficient to suppress fracture, then the fractures will evolve with time to give the characteristic tertiary creep response. Two first order kinetics processes, closure of cracks and healing of cracks, control the healing process. Significantly, volume strain produced by microfractures may lead to changes in the permeability of the salt, which can become a major concern in

  12. Rheological Characteristics of Cement Grout and its Effect on Mechanical Properties of a Rock Fracture

    Science.gov (United States)

    Liu, Quansheng; Lei, Guangfeng; Peng, Xingxin; Lu, Chaobo; Wei, Lai

    2018-02-01

    Grouting reinforcement, which has an obvious strengthening effect on fractured rock mass, has been widely used in various fields in geotechnical engineering. The rheological properties of grout will greatly affect its diffusion radius in rock fractures, and the water-cement ratio is an important factor in determining the grouting flow patterns. The relationship between shear stress and shear rate which could reflect the grout rheological properties, the effects of water-cement ratio, and temperature on the rheological properties of grouting was studied in the laboratory. Besides, a new method for producing fractured rock specimens was proposed and solved the problem of producing natural fractured rock specimens. To investigate the influences of grouting on mechanical properties of a rock fracture, the fractured rock specimens made using the new method were reinforced by grouting on the independent designed grouting platform, and then normal and tangential mechanical tests were carried out on fractured rock specimens. The results showed that the mechanical properties of fractured rock mass are significantly improved by grouting, the peak shear strength and residual strength of rock fractures are greatly improved, and the resistance to deformation is enhanced after grouting. Normal forces affect the tangential behavior of the rock fracture, and the tangential stress strength increases with normal forces. The strength and stability of fractured rock mass are increased by grouting reinforcement.

  13. Aftershocks and triggering processes in rock fracture

    Science.gov (United States)

    Davidsen, J.; Kwiatek, G.; Goebel, T.; Stanchits, S. A.; Dresen, G.

    2017-12-01

    One of the hallmarks of our understanding of seismicity in nature is the importance of triggering processes, which makes the forecasting of seismic activity feasible. These triggering processes by which one earthquake induces (dynamic or static) stress changes leading to potentially multiple other earthquakes are at the core relaxation processes. A specic example of triggering are aftershocks following a large earthquake, which have been observed to follow certain empirical relationships such as the Omori-Utsu relation. Such an empirical relation should arise from the underlying microscopic dynamics of the involved physical processes but the exact connection remains to be established. Simple explanations have been proposed but their general applicability is unclear. Many explanations involve the picture of an earthquake as a purely frictional sliding event. Here, we present experimental evidence that these empirical relationships are not limited to frictional processes but also arise in fracture zone formation and are mostly related to compaction-type events. Our analysis is based on tri-axial compression experiments under constant displacement rate on sandstone and granite samples using spatially located acoustic emission events and their focal mechanisms. More importantly, we show that event-event triggering plays an important role in the presence of large-scale or macrocopic imperfections while such triggering is basically absent if no signicant imperfections are present. We also show that spatial localization and an increase in activity rates close to failure do not necessarily imply triggering behavior associated with aftershocks. Only if a macroscopic crack is formed and its propagation remains subcritical do we observe significant triggering.

  14. Stress, Flow and Particle Transport in Rock Fractures

    Energy Technology Data Exchange (ETDEWEB)

    Koyama, Tomofumi

    2007-09-15

    The fluid flow and tracer transport in a single rock fracture during shear processes has been an important issue in rock mechanics and is investigated in this thesis using Finite Element Method (FEM) and streamline particle tracking method, considering evolutions of aperture and transmissivity with shear displacement histories under different normal stresses, based on laboratory tests. The distributions of fracture aperture and its evolution during shear were calculated from the initial aperture fields, based on the laser-scanned surface roughness features of replicas of rock fracture specimens, and shear dilations measured during the coupled shear-flow-tracer tests in laboratory performed using a newly developed testing apparatus in Nagasaki University, Nagasaki, Japan. Three rock fractures of granite with different roughness characteristics were used as parent samples from which nine plaster replicas were made and coupled shear-flow tests was performed under three normal loading conditions (two levels of constant normal loading (CNL) and one constant normal stiffness (CNS) conditions). In order to visualize the tracer transport, transparent acrylic upper parts and plaster lower parts of the fracture specimens were manufactured from an artificially created tensile fracture of sandstone and the coupled shear-flow tests with fluid visualization was performed using a dye tracer injected from upstream and a CCD camera to record the dye movement. A special algorithm for treating the contact areas as zero-aperture elements was used to produce more accurate flow field simulations by using FEM, which is important for continued simulations of particle transport, but was often not properly treated in literature. The simulation results agreed well with the flow rate data obtained from the laboratory tests, showing that complex histories of fracture aperture and tortuous flow channels with changing normal stresses and increasing shear displacements, which were also captured

  15. Applying Bioaugmentation to Treat DNAPL Sources in Fractured Rock

    Science.gov (United States)

    2017-03-27

    Figure 1. This ESTCP demonstration was focused in the vicinity of Building 8595, adjacent to the location of a reported surface release of PCE ( Earth ...electron donor source, such as vegetable oil, is typically used in passive approaches. When treating a DNAPL source area in fractured rock, there are... vegetable oil) are used. Hydrogen The generation of hydrogen can be used to verify fermentation of electron donor. Metals (Fe, Mn, As) Increase

  16. Analog site for fractured rock characterization. Annual report FY 1995

    International Nuclear Information System (INIS)

    Long, J.C.S.; Loughty, C.; Faybishenko, B.

    1995-10-01

    This report describes the accomplishments of the Analog Site for Fracture Rock Characterization Project during fiscal year 1995. This project is designed to address the problem of characterizing contaminated fractured rock. In order to locate contaminant plumes, develop monitoring schemes, and predict future fate and transport, the project will address the following questions: What parts of the system control flow-geometry of a fracture network? What physical processes control flow and transport? What are the limits on measurements to determine the above? What instrumentation should be used? How should it be designed and implemented? How can field tests be designed to provide information for predicting behavior? What numerical models are good predictors of the behavior of the system? The answers to these question can be used to help plan drilling programs that are likely to intersect plumes and provide effective monitoring of plume movement. The work is done at an open-quotes analogueclose quotes site, i.e., a site that is not contaminated, but has similar geology to sites that are contaminated, in order to develop tools and techniques without the financial, time and legal burdens of a contaminated site. The idea is to develop conceptual models and investigations tools and methodology that will apply to the contaminated sites in the same geologic regimes. The Box Canyon site, chosen for most of this work represents a unique opportunity because the Canyon walls allow us to see a vertical plane through the rock. The work represents a collaboration between the Lawrence Berkeley National Laboratory (LBL), Stanford University (Stanford), Idaho National Engineering Laboratory (INEL) and Parsons Environmental Engineering (Parsons). LBL and Stanford bring extensive experience in research in fractured rock systems. INEL and Parsons bring significant experience with the contamination problem at INEL

  17. Hydrogeologic characterization of a fractured granitic rock aquifer, Raymond, California

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, Andrew J.B. [Univ. of California, Berkeley, CA (United States)

    1993-10-01

    The hydrogeologic properties of a shallow, fractured granitic rock aquifer in the foothills of the Sierra Nevada, California were investigated via the analysis of borehole geophysical logs and pumping tests. The drawdowns produced during these tests are not indicative of any simple conceptual aquifer model, and borehole logs show that the granite is intensely fractured. These observations are suggestive of a complex fracture-flow geometry which is extremely difficult to decipher. However, through the measurement of orientations of individual subsurface fractures from acoustic televiewer logs, and correlation between particular fractures and electrical resistivity and thermal-pulse flowmeter logs, it was found that the aquifer is, in general, comprised of two subhorizontal and nearly parallel zones of unloading fractures. Downhole flowmeter measurements taken in several wells provide further evidence for the inferred dual-layer structure of the aquifer, as well as yield quantitative measures of the contribution of flow from each zone. Analysis of drawdowns in pumped wells reveals that there are zones of relatively high transmissivity immediately around them. It was found that these properties, as well as a nearby zone of lower transmissivity, can account for their observed drawdowns. A numerical model was constructed to test whether these major heterogeneities could also account for the drawdowns in observation wells. This stepwise analysis of both the geophysical and hydrological data resulted in the formulation of a conceptual model of the aquifer which is consistent with observations, and which can account for its behavior when subjected to pumping.

  18. Geophysical study in waste landfill localized above fractured rocks

    Directory of Open Access Journals (Sweden)

    Ariveltom Cosme da Silva

    2011-08-01

    Full Text Available Geophysical survey is an important method for investigation of contaminated areas used in the characterization of contrasting physical properties in the presence of pollutants. This work applied the geophysical methods of Electrical Resistivity and Self Potential in waste landfill, located in Caçapava do Sul city, RS. The landfill is located over fractured metamorphic rocks. Eight lines of electrical profiling with 288 measures of self potential were done. In addition, 83 measurements of direction and dip of fractures were taken. The application of spontaneous potential method permitted to detect the direction of groundwater flow. The electrical resistivity measurements allowed the identification of low-intensity anomalies associated with the presence of leachate. There is a relationship between anomalous zones and the directions of fractures.

  19. Research on fracture analysis, groundwater flow and sorption processes in fractured rocks

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Dae-Ha; Kim, Won-Young; Lee, Seung-Gu [Korea Institute of Geology Mining and Materials, Taejon (KR)] (and others)

    1999-12-01

    Due to increasing demand for numerous industrial facilities including nuclear power plants and waste repositories, the feasibility of rocks masses as sites for the facilities has been a geological issue of concern. Rock masses, in general, comprises systems of fractures which can provide pathways for groundwater flow and may also affect the stability of engineered structures. For the study of groundwater flow and sorption processes in fractured rocks, five boreholes were drilled. A stepwise and careful integration of various data obtained from field works and laboratory experiments were carried out to analyze groundwater flow in fractured rocks as follows; (1) investigation of geological feature of the site, (2) identification and characterization of fracture systems using core and televiewer logs, (3) determination of hydrogeological properties of fractured aquifers using geophysical borehole logging, pumping and slug tests, and continuous monitoring of groundwater level and quality, (4) evaluation of groundwater flow patterns using fluid flow modeling. The results obtained from these processes allow a qualitative interpretation of fractured aquifers in the study area. Column experiments of some reactive radionuclides were also performed to examine sorption processes of the radionuclides including retardation coefficients. In addition, analyses of fracture systems covered (1) reconstruction of the Cenozoic tectonic movements and estimation of frequency indices for the Holocene tectonic movements, (2) determination of distributions and block movements of the Quaternary marine terraces, (3) investigation of lithologic and geotechnical nature of study area, and (4) examination of the Cenozoic volcanic activities and determination of age of the dike swarms. Using data obtained from above mentioned analyses along with data related to earthquakes and active faults, probabilistic approach was performed to determine various potential hazards which may result from the

  20. Spatial statistics for predicting flow through a rock fracture

    International Nuclear Information System (INIS)

    Coakley, K.J.

    1989-03-01

    Fluid flow through a single rock fracture depends on the shape of the space between the upper and lower pieces of rock which define the fracture. In this thesis, the normalized flow through a fracture, i.e. the equivalent permeability of a fracture, is predicted in terms of spatial statistics computed from the arrangement of voids, i.e. open spaces, and contact areas within the fracture. Patterns of voids and contact areas, with complexity typical of experimental data, are simulated by clipping a correlated Gaussian process defined on a N by N pixel square region. The voids have constant aperture; the distance between the upper and lower surfaces which define the fracture is either zero or a constant. Local flow is assumed to be proportional to local aperture cubed times local pressure gradient. The flow through a pattern of voids and contact areas is solved using a finite-difference method. After solving for the flow through simulated 10 by 10 by 30 pixel patterns of voids and contact areas, a model to predict equivalent permeability is developed. The first model is for patterns with 80% voids where all voids have the same aperture. The equivalent permeability of a pattern is predicted in terms of spatial statistics computed from the arrangement of voids and contact areas within the pattern. Four spatial statistics are examined. The change point statistic measures how often adjacent pixel alternate from void to contact area (or vice versa ) in the rows of the patterns which are parallel to the overall flow direction. 37 refs., 66 figs., 41 tabs

  1. Groundwater degassing in fractured rock: Modelling and data comparison

    Energy Technology Data Exchange (ETDEWEB)

    Jarsjoe, J.; Destouni, G. [Royal Inst. of Tech., Stockholm (Sweden). Water Resources Engineering

    1998-11-01

    Dissolved gas may be released from deep groundwater in the vicinity of open boreholes and drifts, where the water pressures are relatively low. Degassing of groundwater may influence observations of hydraulic conditions made in drifts, interpretation of experiments performed close to drifts, and buffer mass and backfill performance, particularly during emplacement and repository closure. Under certain conditions, considerable fracture inflow and transmissivity reductions have been observed during degassing experiments in the field and in the laboratory; such reductions affect the outcome and interpretation of both hydraulic and tracer tests. We develop models for the estimation of the resulting degree of fracture gas saturation and the associated transmissivity reduction due to groundwater degassing in fractured rock. Derived expressions for bubble trapping probability show that fracture aperture variability and correlation length influence the conditions for capillary bubble trapping and gas accumulation. The laboratory observations of bubble trapping in an Aespoe fracture replica are consistent with the prediction of a relatively high probability of bubble trapping in this fracture. The prediction was based on the measured aperture distribution of the Aespoe fracture and the applied hydraulic gradient. Results also show that the conceptualisation of gas and water occupancy in a fracture greatly influences model predictions of gas saturation and relative transmissivity. Images from laboratory degassing experiments indicate that tight apertures are completely filled with water, whereas both gas and water exist in wider apertures under degassing conditions; implementation of this relation in our model resulted in the best agreement between predictions and laboratory observations. Model predictions for conditions similar to those prevailing in field for single fractures at great depths indicate that degassing effects in boreholes should generally be small, unless the

  2. Is the permeability of naturally fractured rocks scale dependent?

    Science.gov (United States)

    Azizmohammadi, Siroos; Matthäi, Stephan K.

    2017-09-01

    The equivalent permeability, keq of stratified fractured porous rocks and its anisotropy is important for hydrocarbon reservoir engineering, groundwater hydrology, and subsurface contaminant transport. However, it is difficult to constrain this tensor property as it is strongly influenced by infrequent large fractures. Boreholes miss them and their directional sampling bias affects the collected geostatistical data. Samples taken at any scale smaller than that of interest truncate distributions and this bias leads to an incorrect characterization and property upscaling. To better understand this sampling problem, we have investigated a collection of outcrop-data-based Discrete Fracture and Matrix (DFM) models with mechanically constrained fracture aperture distributions, trying to establish a useful Representative Elementary Volume (REV). Finite-element analysis and flow-based upscaling have been used to determine keq eigenvalues and anisotropy. While our results indicate a convergence toward a scale-invariant keq REV with increasing sample size, keq magnitude can have multi-modal distributions. REV size relates to the length of dilated fracture segments as opposed to overall fracture length. Tensor orientation and degree of anisotropy also converge with sample size. However, the REV for keq anisotropy is larger than that for keq magnitude. Across scales, tensor orientation varies spatially, reflecting inhomogeneity of the fracture patterns. Inhomogeneity is particularly pronounced where the ambient stress selectively activates late- as opposed to early (through-going) fractures. While we cannot detect any increase of keq with sample size as postulated in some earlier studies, our results highlight a strong keq anisotropy that influences scale dependence.

  3. Drilling and coring methods that minimize the disturbance of cuttings, core, and rock formation in the unsaturated zone, Yucca Mountain, Nevada

    International Nuclear Information System (INIS)

    Hammermeister, D.P.; Blout, D.O.; McDaniel, J.C.

    1985-01-01

    A drilling-and-casing method (Odex 115 system) utilizing air as a drilling fluid was used successfully to drill through various rock types within the unsaturated zone at Yucca Mountain, Nevada. This paper describes this method and the equipment used to rapidly penetrate bouldery alluvial-colluvial deposits, poorly consolidated bedded and nonwelded tuff, and fractured, densely welded tuff to depths of about 130 meters. A comparison of water-content and water-potential data from drill cuttings with similar measurements on rock cores indicates that drill cuttings were only slightly disturbed for several of the rock types penetrated. Coring, sampling, and handling methods were devised to obtain minimally disturbed drive core from bouldery alluvial-colluvial deposits. Bulk-density values obtained from bulk samples dug from nearby trenches were compared to bulk-density values obtained from drive core to determine the effects of drive coring on the porosity of the core. Rotary coring methods utilizing a triple-tube core barrel and air as the drilling fluid were used to obtain core from welded and nonwelded tuff. Results indicate that the disturbance of the water content of the core was minimal. Water-content distributions in alluvium-colluvium were determined before drilling occurred by drive-core methods. After drilling, water-content distributions were determined by nuclear-logging methods. A comparison of the water-content distributions made before and after drilling indicates that Odex 115 drilling minimally disturbs the water content of the formation rock. 10 refs., 12 figs., 4 tabs

  4. Fractal analysis of fractures and microstructures in rocks

    International Nuclear Information System (INIS)

    Merceron, T.; Nakashima, S.; Velde, B.; Badri, A.

    1991-01-01

    Fractal geometry was used to characterize the distribution of fracture fields in rocks, which represent main pathways for material migration such as groundwater flow. Fractal investigations of fracture distribution were performed on granite along Auriat and Shikoku boreholes. Fractal dimensions range between 0.3 and 0.5 according to the different sets of fracture planes selected for the analyses. Shear, tension and compressional modes exhibit different fractal values while the composite fracture patterns are also fractal but with a different, median, fractal value. These observations indicate that the fractal method can be used to distinguish fracture types of different origins in a complex system. Fractal results for Shikoku borehole also correlate with geophysical parameters recorded along, drill-holes such as resistivity and possibly permeability. These results represent the first steps of the fractal investigation along drill-holes. Future studies will be conducted to verify relationships between fractal dimensions and permeability by using available geophysical data. Microstructures and microcracks were analysed in the Inada granite. Microcrack patterns are fractal but fractal dimensions values vary according to both mineral type and orientations of measurement within the mineral. Microcracks in quartz are characterized by more irregular distribution (average D = 0.40) than those in feldspars (D = 0.50) suggesting a different mode of rupture. Highest values of D are reported along main cleavage planes for feldspars or C axis for quartz. Further fractal investigations of microstructure in granite will be used to characterize the potential pathways for fluid migration and diffusion in the rock matrix. (author)

  5. Streaming potential modeling in fractured rock: Insights into the identification of hydraulically active fractures

    Science.gov (United States)

    Roubinet, D.; Linde, N.; Jougnot, D.; Irving, J.

    2016-05-01

    Numerous field experiments suggest that the self-potential (SP) geophysical method may allow for the detection of hydraulically active fractures and provide information about fracture properties. However, a lack of suitable numerical tools for modeling streaming potentials in fractured media prevents quantitative interpretation and limits our understanding of how the SP method can be used in this regard. To address this issue, we present a highly efficient two-dimensional discrete-dual-porosity approach for solving the fluid flow and associated self-potential problems in fractured rock. Our approach is specifically designed for complex fracture networks that cannot be investigated using standard numerical methods. We then simulate SP signals associated with pumping conditions for a number of examples to show that (i) accounting for matrix fluid flow is essential for accurate SP modeling and (ii) the sensitivity of SP to hydraulically active fractures is intimately linked with fracture-matrix fluid interactions. This implies that fractures associated with strong SP amplitudes are likely to be hydraulically conductive, attracting fluid flow from the surrounding matrix.

  6. Simulation of fluid flow in fractured rock: a probabilistic approach

    International Nuclear Information System (INIS)

    Samaniego, J.A.; Priest, S.D.

    1985-02-01

    This report describes the results of a research project designed to investigate the influence of discontinuities on fluid flow through fractured rock masses. The aim has been to provide a rational basis for the assessment of prospective intermediate level radioactive waste repository sites. The results of this work are presented in the form of two groups of FORTRAN computer programs. The first of these is designed to process data obtained from exposed rock faces and thereby provide an unbiased estimate of discontinuity characteristics. The resulting data are input to the second group of programs which generate a two-dimensional random realisation of discontinuity geometry. When appropriate boundary conditions have been specified, the resulting network of channels is solved numerically to determine nodal potentials, flow quantities and equivalent permeabilities. A number of validation runs are presented, together with some parametric studies, to investigate the influence of excavation size and discontinuity geometry on fluid flow. A practical application is given in the form of a case study involving the prediction of fluid flow into a 2.8 m diameter tunnel in water bearing, fractured rock. Finally, the applications and limitations of the programs in site assessment for radioactive waste repositories are discussed. (author)

  7. Applications of stochastic models to solute transport in fractured rocks

    International Nuclear Information System (INIS)

    Gelhar, L.W.

    1987-01-01

    A stochastic theory for flow and solute transport in a single variable aperture fracture bounded by sorbing porous matrix into which solutes may diffuse, is developed using a perturbation approximation and spectral solution techniques which assume local statistical homogeneity. The theory predicts that the effective aperture of the fracture for mean solute displacement will be larger than the aperture required to calculate the large-scale flow resistance of the fracture. This ratio of apertures is a function of the variance of the logarithm of the apertures. The theory also predicts the macrodispersion coefficient for large-scale transport in the fracture. The resulting macrodispersivity is proportional to the variance of the logaperture and to its correlation scale. When variable surface sorption is included, it is found that the macrodispersivity is increased significantly, in some cases more than an order of magnitude. It is also shown that the effective retardation coefficient for the sorptively heterogeneous fracture is found by simply taking the arithmetic mean of the local surface sorption coefficient. Matrix diffusion is also shown to increase the fracture macrodispesivity at very large times. A reexamination of the results of four different field tracer tests in crystalline rock in Sweden and Canada shows aperture ratios and dispersivities that are consistent with the stochastic theory. The variance of the natural logarithm of the aperture is found to be in the range of 3 to 6 and the correlation scales for logaperture ranges from .2 to 1.2 meters. Detailed recommendations for additional field investigations at scales ranging from a few meters up to a kilometer are presented. (orig.)

  8. Upscaling of permeability field of fractured rock system: Numerical examples

    KAUST Repository

    Bao, K.; Salama, Amgad; Sun, S.

    2012-01-01

    When the permeability field of a given porous medium domain is heterogeneous by the existence of randomly distributed fractures such that numerical investigation becomes cumbersome, another level of upscaling may be required. That is such complex permeability field could be relaxed (i.e., smoothed) by constructing an effective permeability field. The effective permeability field is an approximation to the real permeability field that preserves certain quantities and provides an overall acceptable description of the flow field. In this work, the effective permeability for a fractured rock system is obtained for different coarsening scenarios starting from very coarse mesh all the way towards the fine mesh simulation. In all these scenarios, the effective permeability as well as the pressure at each cell is obtained. The total flux at the exit boundary is calculated in all these cases, and very good agreement is obtained.

  9. The moderately fractured rock experiment: Background and overview

    International Nuclear Information System (INIS)

    Jensen, M.R.

    2001-01-01

    The Moderately Fractured Rock (MFR) experiment is conducted at Atomic Energy of Canada Limited's Underground Research Laboratory (URL) as part of Ontario Power Generation's Deep Geologic Repository Technology Program. The MFR experiment was initiated in the mid-1990s with the purpose of advancing the understanding of mass transport in MFR (fractures 1-5/m, k ≅ 10 -15 m 2 ) in which groundwater flow and solute migration occurs through a network of interconnected fractures. The experimental program has involved a series of multi-well forced gradient tracer tests at scales of 10-50 m within a ≅ 100,000 m 3 volume of MFR accessed from the 240 m level of the URL. The tracer tests conducted with non-reactive, reactive and colloidal tracers have served to explore the applicability of continuum models for prediction of groundwater flow and mass transport. Recently, a Modeling Task Force was created to re-examine tracer test experimental methodologies, MFR flow and transport conceptual models and provide a broader forum in which to apply alternative dual-permeability, discrete fracture and hybrid mathematical codes for flow system analysis. This paper provides a description of the MFR experiment, preliminary research findings and plans for the future

  10. Large-Scale True Triaxial Apparatus for Geophysical Studies in Fractured Rock

    KAUST Repository

    Garcia, A. V.

    2018-05-12

    The study of fractured rock masses in the laboratory remains challenging because of the large specimen sizes and bulky loading systems that are required. This article presents the design, structural analysis, and operation of a compact and self-reacting true triaxial device for fractured rock. The frame subjects a 50 cm by 50 cm by 50 cm fractured rock specimen to a maximum stress of 3 MPa along three independent axes. Concurrent measurements include long-wavelength P-wave propagation, passive acoustic emission monitoring, deformations, and thermal measurements. The device can accommodate diverse research, from rock mass properties and geophysical fractured rock characterizations, to coupled hydro-chemo-thermo-mechanical processes, drilling, and grouting. Preliminary wave propagation data gathered under isotropic and anisotropic stress conditions for an assembly of 4,000 rock blocks demonstrate the system’s versatility and provide unprecedented information related to long-wavelength propagation in fractured rock under various stress anisotropies.

  11. Large-Scale True Triaxial Apparatus for Geophysical Studies in Fractured Rock

    KAUST Repository

    Garcia, A. V.; Rached, R. M.; Santamarina, Carlos

    2018-01-01

    The study of fractured rock masses in the laboratory remains challenging because of the large specimen sizes and bulky loading systems that are required. This article presents the design, structural analysis, and operation of a compact and self-reacting true triaxial device for fractured rock. The frame subjects a 50 cm by 50 cm by 50 cm fractured rock specimen to a maximum stress of 3 MPa along three independent axes. Concurrent measurements include long-wavelength P-wave propagation, passive acoustic emission monitoring, deformations, and thermal measurements. The device can accommodate diverse research, from rock mass properties and geophysical fractured rock characterizations, to coupled hydro-chemo-thermo-mechanical processes, drilling, and grouting. Preliminary wave propagation data gathered under isotropic and anisotropic stress conditions for an assembly of 4,000 rock blocks demonstrate the system’s versatility and provide unprecedented information related to long-wavelength propagation in fractured rock under various stress anisotropies.

  12. Rock fracture grouting with microbially induced carbonate precipitation

    Science.gov (United States)

    Minto, James M.; MacLachlan, Erica; El Mountassir, Gráinne; Lunn, Rebecca J.

    2016-11-01

    Microbially induced carbonate precipitation has been proposed for soil stabilization, soil strengthening, and permeability reduction as an alternative to traditional cement and chemical grouts. In this paper, we evaluate the grouting of fine aperture rock fractures with calcium carbonate, precipitated through urea hydrolysis, by the bacteria Sporosarcina pasteurii. Calcium carbonate was precipitated within a small-scale and a near field-scale (3.1 m2) artificial fracture consisting of a rough rock lower surfaces and clear polycarbonate upper surfaces. The spatial distribution of the calcium carbonate precipitation was imaged using time-lapse photography and the influence on flow pathways revealed from tracer transport imaging. In the large-scale experiment, hydraulic aperture was reduced from 276 to 22 μm, corresponding to a transmissivity reduction of 1.71 × 10-5 to 8.75 × 10-9 m2/s, over a period of 12 days under constantly flowing conditions. With a modified injection strategy a similar three orders of magnitude reduction in transmissivity was achieved over a period of 3 days. Calcium carbonate precipitated over the entire artificial fracture with strong adhesion to both upper and lower surfaces and precipitation was controlled to prevent clogging of the injection well by manipulating the injection fluid velocity. These experiments demonstrate that microbially induced carbonate precipitation can successfully be used to grout a fracture under constantly flowing conditions and may be a viable alternative to cement based grouts when a high level of hydraulic sealing is required and chemical grouts when a more durable grout is required.

  13. A Rock Mechanics and Coupled Hydro mechanical Analysis of Geological Repository of High Level Nuclear Waste in Fractured Rocks

    International Nuclear Information System (INIS)

    Min, Kibok

    2011-01-01

    This paper introduces a few case studies on fractured hard rock based on geological data from Sweden, Korea is one of a few countries where crystalline rock is the most promising rock formation as a candidate site of geological repository of high level nuclear waste. Despite the progress made in the area of rock mechanics and coupled hydro mechanics, extensive site specific study on multiple candidate sites is essential in order to choose the optimal site. For many countries concerned about the safe isolation of nuclear wastes from the biosphere, disposal in a deep geological formation is considered an attractive option. In geological repository, thermal loading continuously disturbs the repository system in addition to disturbances a recent development in rock mechanics and coupled hydro mechanical study using DFN(Discrete Fracture Network) - DEM(Discrete Element Method) approach mainly applied in hard, crystalline rock containing numerous fracture which are main sources of deformation and groundwater flow

  14. Developing two-phase flow modelling concepts for rock fractures

    Energy Technology Data Exchange (ETDEWEB)

    Keto, V. (Fortum Nuclear Services Oy, Espoo (Finland))

    2010-01-15

    The Finnish nuclear waste disposal company, Posiva Oy, is planning an underground repository for spent nuclear fuel to be constructed on the island of Olkiluoto on the south-west coast of Finland. One element of the site investigations conducted at Olkiluoto is the excavation of the underground rock characterisation facility (ONKALO) that will be extended to the final disposal depth (approximately -400 m). The bedrock around the excavated tunnel volume is fully saturated with groundwater, which water commonly contains a mixture of dissolved gases. These gases remain dissolved due to the high hydrostatic pressure. During tunnel excavation work the natural hydrostatic pressure field is disturbed and the water pressure will decrease close to the atmospheric pressure in the immediate vicinity of the tunnel. During this pressure drop two-phase flow conditions (combined flow of both water and gas) may develop in the vicinity of the underground opening, as the dissolved gas is exsoluted under the low pressure (the term exsolution refers here to release of the dissolved gas molecules from the water phase into a separate gas phase). This report steers towards concept development for numerical two-phase flow modeling for fractured rock. The focus is on the description of gas phase formation process under disturbed hydraulic conditions by exsolution of dissolved gases from groundwater, and on understanding the effects of a possibly formed gas phase on groundwater flow conditions in rock fractures. A mathematical model of three mutually coupled nonlinear partial differential equations for two-phase flow is presented and corresponding constitutional relationships are introduced and discussed. Illustrative numerical simulations are performed in a simplified setting using COMSOL Multiphysics 3.5a - software package. Shortcomings and conceptual problems are discussed. (orig.)

  15. Developing two-phase flow modelling concepts for rock fractures

    International Nuclear Information System (INIS)

    Keto, V.

    2010-01-01

    The Finnish nuclear waste disposal company, Posiva Oy, is planning an underground repository for spent nuclear fuel to be constructed on the island of Olkiluoto on the south-west coast of Finland. One element of the site investigations conducted at Olkiluoto is the excavation of the underground rock characterisation facility (ONKALO) that will be extended to the final disposal depth (approximately -400 m). The bedrock around the excavated tunnel volume is fully saturated with groundwater, which water commonly contains a mixture of dissolved gases. These gases remain dissolved due to the high hydrostatic pressure. During tunnel excavation work the natural hydrostatic pressure field is disturbed and the water pressure will decrease close to the atmospheric pressure in the immediate vicinity of the tunnel. During this pressure drop two-phase flow conditions (combined flow of both water and gas) may develop in the vicinity of the underground opening, as the dissolved gas is exsoluted under the low pressure (the term exsolution refers here to release of the dissolved gas molecules from the water phase into a separate gas phase). This report steers towards concept development for numerical two-phase flow modeling for fractured rock. The focus is on the description of gas phase formation process under disturbed hydraulic conditions by exsolution of dissolved gases from groundwater, and on understanding the effects of a possibly formed gas phase on groundwater flow conditions in rock fractures. A mathematical model of three mutually coupled nonlinear partial differential equations for two-phase flow is presented and corresponding constitutional relationships are introduced and discussed. Illustrative numerical simulations are performed in a simplified setting using COMSOL Multiphysics 3.5a - software package. Shortcomings and conceptual problems are discussed. (orig.)

  16. Fractures inside crystalline rocks. Effects of deformations on fluid circulations

    International Nuclear Information System (INIS)

    Gentier, S.

    2005-01-01

    The modeling of fluid flows inside granite massifs is an important task for the evaluation of the feasibility of radioactive waste storage inside such formations. This document makes a synthesis of the works carried out since about 15 years, in particular by the French bureau of geological and mining research (BRGM), about the hydro-mechanical behaviour of a fracture and about the hydrodynamical characterization of fracture networks inside crystalline rocks: 1 - introduction; 2 - hydro-mechanical behaviour under normal stress: experimental results (hydro-mechanical behaviour, flow regimes, mechanical behaviour, test protocol, complementary tests, influence of samples size), geometrical interpretation of experimental results (relation with walls geometry, relation with voids geometry, relation with contacts geometry), hydro-mechanical modeling (hydraulic modeling, mechanical modeling); 3 - from the hydro-mechanical behaviour under normal stress to the coupling with heat transfers and chemistry: experiment for the study of the chemo-thermo-hydro-mechanical coupling (experimental results, relation with walls morphology), thermo-hydro-mechanical experiments, thermo-hydro-chemical experiments with fractures, conclusions; 4 - hydro-mechanical behaviour during shear: experimental results, geometrical interpretation (relation with the geometry of damaged zones, relation with voids geometry, relation with walls geometry), hydro-mechanical modeling (mechanical modeling, hydro-mechanical modeling of the behaviour during shear). (J.S.)

  17. The application of positron emission tomography to the study of mass transfer in fractured rock

    International Nuclear Information System (INIS)

    Gilling, D.; Jefferies, N.L.; Fowles, P.; Hawkesworth, M.R.; Parker, D.J.

    1991-06-01

    Water flow in hard rocks takes place dominantly in fractures. In order to predict the transport of dissolved radioelements through a fractured rock it is necessary to determine both the geometry of the fracture network and the hydraulic properties of the individual fractures. This paper describes a technique for studying mass transfer in a single fracture. The technique is positron emission tomography (PET) and it offers the potential for visualising quantitatively the migration of dissolved tracers. Preliminary experiments have been undertaken involving the flow of Na-22 and F-18 labelled solutions through artificial fractures. The results demonstrate that PET is well suited to this application. (author)

  18. Studies on groundwater transport in fractured crystalline rock under controlled conditions using nonradioactive tracers

    International Nuclear Information System (INIS)

    Gustafsson, E.; Klockars, C.-E.

    1981-04-01

    The purpose of the investigation has been study the following parameters along existing fractures between two boreholes: hydraulic properties of rock mass and fractures; adsorptive properties of some selected tracers during transport along fractures; dispersivity and dilution of tracers during transport in fractures; kinematic porosity of fractured bedrock. The procedure has been to determine the hydraulic properties of a rock mass by means of conventional hydraulic testing methods in 100 m deep boreholes, and to study transport mechanisms and properties of selected tracers in a selected fracture zone between two boreholes. (Auth.)

  19. Reactive solute transport in an asymmetrical fracture-rock matrix system

    Science.gov (United States)

    Zhou, Renjie; Zhan, Hongbin

    2018-02-01

    The understanding of reactive solute transport in a single fracture-rock matrix system is the foundation of studying transport behavior in the complex fractured porous media. When transport properties are asymmetrically distributed in the adjacent rock matrixes, reactive solute transport has to be considered as a coupled three-domain problem, which is more complex than the symmetric case with identical transport properties in the adjacent rock matrixes. This study deals with the transport problem in a single fracture-rock matrix system with asymmetrical distribution of transport properties in the rock matrixes. Mathematical models are developed for such a problem under the first-type and the third-type boundary conditions to analyze the spatio-temporal concentration and mass distribution in the fracture and rock matrix with the help of Laplace transform technique and de Hoog numerical inverse Laplace algorithm. The newly acquired solutions are then tested extensively against previous analytical and numerical solutions and are proven to be robust and accurate. Furthermore, a water flushing phase is imposed on the left boundary of system after a certain time. The diffusive mass exchange along the fracture/rock matrixes interfaces and the relative masses stored in each of three domains (fracture, upper rock matrix, and lower rock matrix) after the water flushing provide great insights of transport with asymmetric distribution of transport properties. This study has the following findings: 1) Asymmetric distribution of transport properties imposes greater controls on solute transport in the rock matrixes. However, transport in the fracture is mildly influenced. 2) The mass stored in the fracture responses quickly to water flushing, while the mass stored in the rock matrix is much less sensitive to the water flushing. 3) The diffusive mass exchange during the water flushing phase has similar patterns under symmetric and asymmetric cases. 4) The characteristic distance

  20. A Record of Uranium-Series Transport in Fractured, Unsaturated Tuff at Nopal I, Sierra Peña Blanca, Chihuahua, Mexico

    Science.gov (United States)

    Denton, J.; Goldstein, S. J.; Paviet, P.; Nunn, A. J.; Amato, R. S.; Hinrichs, K. A.

    2015-12-01

    In this study we utilize U-series disequilibria measurements to investigate mineral fluid interactions and the role fractures play in the geochemical evolution of an analogue for a high level nuclear waste repository, the Nopal I uranium ore deposit. Samples of fracture-fill materials have been collected from a vertical drill core and surface fractures. High uranium concentrations in these materials (12-7700 ppm) indicate U mobility and transport from the deposit in the past. U concentrations generally decrease with horizontal distance away from the ore deposit but show no trend with depth. Isotopic activity ratios indicate a complicated geochemical evolution in terms of the timing and extent of actinide mobility, possibly due to changing environmental (redox) conditions over the history of the deposit. 234U/238U activity ratios are generally distinct from secular equilibrium and indicate some degree of open system U behavior during the past 1.2 Ma. However, calculated closed system 238U-234U-230Th model ages are generally >313 ka and >183 ka for the surface fracture and drill core samples respectively, suggesting closed system behavior for U and Th over this most recent time period. Whole rock isochrons drawn for the drill core samples show that at two of three depths fractures have remained closed with respect to U and Th mobility for >200 ka. However, open system behavior for U in the last 350 ka is suggested at 67 m depth. 231Pa/235U activity ratios within error of unity suggest closed system behavior for U and Pa for at least the past 185 ka. 226Ra/230Th activity ratios are typically <1 (0.7-1.2), suggesting recent (<8 ka) radium loss and mobility due to ongoing fluid flow in the fractures. Overall, the mainly closed system behavior of U-Th-Pa over the past ~200 ka provides one indicator of the geochemical immobility of these actinides over long time-scales for potential nuclear waste repositories sited in fractured, unsaturated tuff.

  1. Mobilities of radionuclides in fresh and fractured crystalline rock

    International Nuclear Information System (INIS)

    Torstenfelt, B.; Ittner, T.; Allard, B.; Andersson, K.; Olofsson, U.

    1982-12-01

    Sorption and migration of technetium, cesium and americium on fracture surfaces and fresh surfaces of granites taken from drilling cores from the Finnsjoen and Studsvik areas and the Stripa mine are reported. The three elements were used as reference elements with different chemistry and behaviour in water; under the conditions used in the experiments technetium exists as the heptavalent TcO -4 -ion, cesium as the non-complexed monovalent cation Cs + and americium as the strongly hydrolysed Am(OH)super (3-x) (x-1-4). The waters used were synthetic groundwaters representative of waters from the drilling holes. After the exposure of the fracture samples to spiked groundwater solutions for a period of three up to six months the penetration depths and concentration profiles were analysed and autoradiographs of cesium and americium distribution vs depth were taken. The sorption of technetium was found to be negligible. The transport of TcO -4 depends on accessibility to fractures and micro-fissures in the rock. Cesium is sorbed through an ion-exchange process. Migration of cesium depends not only on the transport in water into fractures and micro-fissures, but also on migration through mineral veins with a high CEC. Americium is strongly sorbed on most solid surfaces and did not migrate significantly during the contact time of three months. The diffusivity in granite was found to be around 10 - 13 m 2 /s for cesium; preliminary values for technetium and americium were 10 - 12 m 2 /s and less than 10 - 16 m 2 /s, respectively. (Authors)

  2. Measurement of field-saturated hydraulic conductivity on fractured rock outcrops near Altamura (Southern Italy) with an adjustable large ring infiltrometer

    Science.gov (United States)

    Caputo, Maria C.; de Carlo, L.; Masciopinto, C.; Nimmo, J.R.

    2010-01-01

    Up to now, field studies set up to measure field-saturated hydraulic conductivity to evaluate contamination risks, have employed small cylinders that may not be representative of the scale of measurements in heterogeneous media. In this study, a large adjustable ring infiltrometer was designed to be installed on-site directly on rock to measure its field-saturated hydraulic conductivity. The proposed device is inexpensive and simple to implement, yet also very versatile, due to its large adjustable diameter that can be fixed on-site. It thus allows an improved representation of the natural system's heterogeneity, while also taking into consideration irregularities in the soil/rock surface. The new apparatus was tested on an outcrop of karstic fractured limestone overlying the deep Murge aquifer in the South of Italy, which has recently been affected by untreated sludge disposal, derived from municipal and industrial wastewater treatment plants. The quasi-steady vertical flow into the unsaturated fractures was investigated by measuring water levels during infiltrometer tests. Simultaneously, subsurface electrical resistivity measurements were used to visualize the infiltration of water in the subsoil, due to unsaturated water flow in the fractures. The proposed experimental apparatus works well on rock outcrops, and allows the repetition of infiltration tests at many locations in order to reduce model uncertainties in heterogeneous media. ?? 2009 Springer-Verlag.

  3. Mechanical interaction between swelling compacted clay and fractured rock, and the leaching of clay colloids

    NARCIS (Netherlands)

    Grindrod, P.; Peletier, M.A.; Takase, H.

    1999-01-01

    We consider the interaction between a saturated clay buffer layer and a fractured crystalline rock engineered disturbed zone. Once saturated, the clay extrudes into the available rock fractures, behaving as a compressible non-Newtonian fluid. We discuss the modelling implications of published

  4. Folding and fracturing of rock adjacent to salt diapirs

    Science.gov (United States)

    Rowan, Mark G.

    2017-04-01

    When John Ramsay wrote his groundbreaking book in 1967, deformation around salt diapirs was not something he covered. At the time, most geologists considered diapirs to form due to density inversion, rising through thick overlying strata due to buoyancy. In doing so, salt was thought to shove aside the younger rocks, shearing and fracturing them in drag folds and supposedly producing "salt gouge". Even after it was realized that the majority of diapirs spend most of their history growing at or just beneath the surface, the relative rise of salt and sinking of minibasins were (and are) still thought by many to be accommodated in part by shear and fracturing of rocks in a collar zone around the salt. There are two arguments against this model. The first is mechanical: whereas halite behaves as a viscous fluid, even young sediment deforms as a brittle material with layer anisotropy. Thus, the salt-sediment interface is the outer margin of an intrasalt shear zone caused by viscous drag against the diapir margin. The velocity of salt flow decreases dramatically toward the edge of the diapir, so that the outermost salt effectively doesn't move. Hence, no shear or fracturing is expected in surrounding strata. The second and more important argument is that empirical field data do not support the idea of drag folds and associated deformation. Certainly, strata are typically folded and thinned adjacent to diapirs. However, stratal upturn is generated by monoclinal drape folding of the diapir roof over the edge of the rising salt, and thinning is caused by deposition onto the bathymetric highs formed by the diapirs, often supplemented by roof erosion and slumping. Halokinetic sequences observed in numerous salt basins (e.g., Paradox Basin, La Popa Basin, Spanish Pyrenees, Sivas Basin, Zagros Mountains, Kuqa Basin) contain no diapir-parallel shear zones and minimal thinning and fracturing caused by diapir rise. Even megaflaps, in which strata extend for kilometers up the sides

  5. Proceedings of the International Symposium on Dynamics of Fluids in Fractured Rocks: Concepts and Recent Advances

    Energy Technology Data Exchange (ETDEWEB)

    Faybishenko, B. (ed.)

    1999-02-01

    This publication contains extended abstracts of papers presented at the International Symposium ''Dynamics of Fluids in Fractured Rocks: Concepts and Recent Advances'' held at Ernest Orlando Lawrence Berkeley National Laboratory on February 10-12, 1999. This Symposium is organized in Honor of the 80th Birthday of Paul A. Witherspoon, who initiated some of the early investigations on flow and transport in fractured rocks at the University of California, Berkeley, and at Lawrence Berkeley National Laboratory. He is a key figure in the development of basic concepts, modeling, and field measurements of fluid flow and contaminant transport in fractured rock systems. The technical problems of assessing fluid flow, radionuclide transport, site characterization, modeling, and performance assessment in fractured rocks remain the most challenging aspects of subsurface flow and transport investigations. An understanding of these important aspects of hydrogeology is needed to assess disposal of nu clear wastes, development of geothermal resources, production of oil and gas resources, and remediation of contaminated sites. These Proceedings of more than 100 papers from 12 countries discuss recent scientific and practical developments and the status of our understanding of fluid flow and radionuclide transport in fractured rocks. The main topics of the papers are: Theoretical studies of fluid flow in fractured rocks; Multi-phase flow and reactive chemical transport in fractured rocks; Fracture/matrix interactions; Hydrogeological and transport testing; Fracture flow models; Vadose zone studies; Isotopic studies of flow in fractured systems; Fractures in geothermal systems; Remediation and colloid transport in fractured systems; and Nuclear waste disposal in fractured rocks.

  6. Flow Mode Dependent Partitioning Processes of Preferential Flow Dynamics in Unsaturated Fractures - Findings From Analogue Percolation Experiments

    Science.gov (United States)

    Kordilla, J.; Noffz, T.; Dentz, M.; Sauter, M.

    2017-12-01

    To assess the vulnerability of an aquifer system it is of utmost importance to recognize the high potential for a rapid mass transport offered by ow through unsaturated fracture networks. Numerical models have to reproduce complex effects of gravity-driven flow dynamics to generate accurate predictions of flow and transport. However, the non-linear characteristics of free surface flow dynamics and partitioning behaviour at unsaturated fracture intersections often exceed the capacity of classical volume-effective modelling approaches. Laboratory experiments that manage to isolate single aspects of the mass partitioning process can enhance the understanding of underlying dynamics, which ultimately influence travel time distributions on multiple scales. Our analogue fracture network consists of synthetic cubes with dimensions of 20 x 20 x 20 cm creating simple geometries of a single or a cascade of consecutive horizontal fractures. Gravity-driven free surface flow (droplets; rivulets) is established via a high precision multichannel dispenser at flow rates ranging from 1.5 to 4.5 ml/min. Single-inlet experiments show the influence of variable flow rate, atmospheric pressure and temperature on the stability of flow modes and allow to delineate a droplet and rivulet regime. The transition between these regimes exhibits mixed flow characteristics. In addition, multi-inlet setups with constant total infow rates decrease the variance induced by erratic free-surface flow dynamics. We investigate the impacts of variable aperture widths, horizontal offsets of vertical fracture surfaces, and alternating injection methods for both flow regimes. Normalized fracture inflow rates allow to demonstrate and compare the effects of variable geometric features. Firstly, the fracture filling can be described by plug flow. At later stages it transitions into a Washburn-type flow, which we compare to an analytical solution for the case of rivulet flow. Observations show a considerably

  7. Evaluation of fracturing process of soft rocks at great depth by AE measurement and DEM simulation

    International Nuclear Information System (INIS)

    Aoki, Kenji; Mito, Yoshitada; Kurokawa, Susumu; Matsui, Hiroya; Niunoya, Sumio; Minami, Masayuki

    2007-01-01

    The authors developed the stress-based evaluation system of EDZ by AE monitoring and Distinct Element Method (DEM) simulation. In order to apply this system to the soft rock site, the authors try to grasp the relationship between AE parameters, stress change and rock fracturing process by performing the high stiffness tri-axial compression tests including AE measurements on the soft rock samples, and its simulations by DEM using bonded particle model. As the result, it is found that change in predominant AE frequency is effective to evaluate fracturing process in sedimentary soft rocks, and the relationship between stress change and fracturing process is also clarified. (author)

  8. Fracture Analysis of basement rock: A case example of the Eastern Part of the Peninsular Malaysia

    International Nuclear Information System (INIS)

    Shamsuddin, A; Ghosh, D

    2015-01-01

    In general, reservoir rocks can be defined into carbonates, tight elastics and basement rocks. Basement rocks came to be highlighted as their characteristics are quite complicated and remained as a significant challenge in exploration and production area. Motivation of this research is to solve the problem in some area in the Malay Basin which consist fractured basement reservoirs. Thus, in order to increase understanding about their characteristic, a study was conducted in the Eastern part of the Peninsular Malaysia. The study includes the main rock types that resemble the offshore rocks and analysis on the factors that give some effect on fracture characteristic that influence fracture systems and fracture networks. This study will allow better fracture prediction which will be beneficial for future hydrocarbon prediction in this region

  9. Calculation of gas migration in fractured rock - a continuum approach

    International Nuclear Information System (INIS)

    Braester, C.

    1987-09-01

    A study of gas migration from low level radioactive repositories in which the fractured rock mass was conceptualized as a continuum, was carried out by the aid of a computer program based on a finite difference numerical method of solution to the equations of flow. The calculations are intended to correspond to the prevailing in the Forsmark low level repository area where radioactive waste repository caverns are planned to be located at a depth of about 50 metres below the sea level. Calculations were worked out for a constant gas flow rate equivalent to a gas production of 20 000 normal cubic metres per year. The investigated flow domain was a vertical cross-section passing through the repository. The results show that in the empty cavern the gas formed in the cavern moves almost instantaneously upward amd accumulates below the roof of the cavern. (orig./DG)

  10. Hydro-thermo-mechanical response of a fractured rock block

    International Nuclear Information System (INIS)

    Kelkar, S.; Zyvoloski, G.

    1990-01-01

    Hydro-thermo-mechanical effects in fractured rocks are important in many engineering applications and geophysical processes. Modeling these effects is made difficult by the fact that the governing equations are nonlinear and coupled, and the problems to be solved are three dimensional. In this paper we describe a numerical code developed for this purpose. The code is finite element based to allow for complicated geometries, and the time differencing is implicit, allowing for large time steps. The use of state-of-the-art equation solvers has resulted in a practical code. The code is capable of fully three dimensional simulations, however, in this paper we consider only the case of two dimensional heat and mass flow coupled to one dimensional deformation. Partial verification of the code is obtained by comparison with published semianalytical results. Several examples are presented to demonstrate the effects of matrix expansion, due to pore pressure and heating, on fracture opening due to fluid injection. 16 refs., 11 figs

  11. Transient diffusion from a waste solid into water-saturated, fractured porous rock

    International Nuclear Information System (INIS)

    Ahn, J.; Chambre, P.L.; Pigford, T.H.; Lee, W.W.-L.

    1989-09-01

    Numerical illustrations for transient mass transfer from an infinitely long cylinder intersected by a planar fracture are shown based on Chambre's exact analytical solutions. The concentration at the cylinder surface is maintained at the solubility. In the fracture contaminant diffuses in the radial direction. In the rock matrix three-dimensional diffusion is assumed in the cylindrical coordinate. No advection is assumed. Radioactive decay and sorption equilibrium are included. Radioactive decay enhances the mass transfer from the cylinder. Due to the presence of the fracture, the mass flux from the cylinder to the rock matrix becomes smaller, but the fracture effect is limited in the vicinity of the fracture in early times. Even though the fracture is assumed to be a faster diffusion path than the rock matrix, the larger waste surface exposed to the matrix and the greater assumed matrix sorption result in greater release rate to the matrix than to the fracture. 8 refs., 4 figs

  12. On the movement of a liquid front in an unsaturated, fractured porous medium, Part 1

    International Nuclear Information System (INIS)

    Nitao, J.J.; Buscheck, T.A.

    1989-06-01

    The primary aim of this paper is to present approximate analytical solutions of the fracture flow which gives the position of the liquid fracture front as a function of time. These solutions demonstrate that the liquid movement in the fracture can be classified into distinctive time periods, or flow regimes. It is also shown that when plotted versus time using a log-log scale, the liquid fracture front position asymptotically approaches a series of line segments. Two-dimensional numerical simulations were run utilizing input data applicable to the densely welded, fractured tuff found at Yucca Mountain in order to confirm these observations. 19 refs., 15 figs., 8 tabs

  13. Study on flow and mass transport through fractured soft sedimentary rocks (Contact research)

    International Nuclear Information System (INIS)

    Shimo, Michito; Kumamoto, Sou; Maekawa, Keisuke

    2007-03-01

    It is important for safety assessment of HLW geological disposal to evaluate groundwater flow and mass transport in deep underground accurately. Though it is considered that the mass transport in sedimentary rock occurs in pores between grains mainly, fractures of sedimentary rock can be main paths. The objective of this study is to establish a conceptual model for flow and mass transport in fractured soft sedimentary rock. In previous study, a series of laboratory hydraulic and tracer tests and numerical analyses were carried out using sedimentary rock specimens obtained from Koetoi and Wakkanai formation. Single natural fractured cores and rock block specimen were used for the tests and analyses. The results indicated that the matrix diffusion played an important role for mass transport in the fractured soft sedimentary rocks. In this study, the following two tasks were carried out: (1) laboratory hydraulic and tracer experiments of rock cores of Koetoi and Wakkanai formation obtained at HDB-9, HDB-10 and HDB-11 boreholes and a rock block specimen, Wakkanai formation, obtained at an outcrop in the Horonobe area, (2) a numerical study on the conceptual model of flow and mass transport through fractured soft sedimentary rocks. Non-sorbing tracer experiments using naturally fractured cores and rock block specimens were carried out. Pottasium iodide was used as a tracer. The obtained breakthrough curves were interpreted and fitted by using a numerical simulator, and mass transport parameters, such as longitudinal dispersivity, matrix diffusion coefficient, transport aperture, were obtained. Mass transport simulations using a fracture network model, a continuum model and a double porosity model were performed to study the applicability of continuum model and double porosity model for transport in fractured sedimentary rock. (author)

  14. Convective heat transfer of supercritical CO_2 in a rock fracture for enhanced geothermal systems

    International Nuclear Information System (INIS)

    Zhang, Le; Jiang, Peixue; Wang, Zhenchuan; Xu, Ruina

    2017-01-01

    Highlights: • Contrasting experiments between a rough and a smooth fracture were performed. • A numerical model of rough fracture was reconstructed based on CT scanning data. • Heat transfer in rough fracture was affected by channeling and disturbance effects. - Abstract: Convective heat transfer characteristics of supercritical pressure fluid in a rock fracture are important for building an accurate heat transfer model of enhanced geothermal systems. This paper presents experimental investigations of laminar convection heat transfer of supercritical pressure CO_2 in an artificial smooth parallel-plate fracture and a rough and tortuous fracture that was created using the Brazilian technique. Hot rock with a relatively high initial temperature reserves more heat, which can ensure a larger heat extraction rate for a longer time when cold fluid flows through the fracture. Compared with the smooth parallel-plate fracture, CO_2 flowing through the rough and tortuous fracture with an equivalent hydraulic aperture extracted less heat from the hot rock due to the less efficient heat exchange in a rough fracture caused by channeling effect. This was illustrated by numerical simulation results of the reconstructed fracture based on micro-computed tomography scan data. The overall Nusselt number obtained from the numerical results was larger in a rough fracture with a larger Reynolds number due to disturbance effect on the boundary layer development. The heat transfer performance in a rough fracture is therefore influenced by interactions of the channeling and disturbance effects caused by the tortuous flow path.

  15. Introduction to numerical modeling of thermohydrologic flow in fractured rock masses

    International Nuclear Information System (INIS)

    Wang, J.S.Y.

    1980-01-01

    More attention is being given to the possibility of nuclear waste isolation in hard rock formations. The waste will generate heat which raises the temperature of the surrounding fractured rock masses and induces buoyancy flow and pressure change in the fluid. These effects introduce the potential hazard of radionuclides being carried to the biosphere, and affect the structure of a repository by stress changes in the rock formation. The thermohydrological and thermomechanical responses are determined by the fractures as well as the intact rock blocks. The capability of modeling fractured rock masses is essential to site characterization and repository evaluation. The fractures can be modeled either as a discrete system, taking into account the detailed fracture distributions, or as a continuum representing the spatial average of the fractures. A numerical model is characterized by the governing equations, the numerical methods, the computer codes, the validations, and the applications. These elements of the thermohydrological models are discussed. Along with the general review, some of the considerations in modeling fractures are also discussed. Some remarks on the research needs in modeling fractured rock mass conclude the paper

  16. MULTI-ATTRIBUTE SEISMIC/ROCK PHYSICS APPROACH TO CHARACTERIZING FRACTURED RESERVOIRS

    Energy Technology Data Exchange (ETDEWEB)

    Gary Mavko

    2000-10-01

    This project consists of three key interrelated Phases, each focusing on the central issue of imaging and quantifying fractured reservoirs, through improved integration of the principles of rock physics, geology, and seismic wave propagation. This report summarizes the results of Phase I of the project. The key to successful development of low permeability reservoirs lies in reliably characterizing fractures. Fractures play a crucial role in controlling almost all of the fluid transport in tight reservoirs. Current seismic methods to characterize fractures depend on various anisotropic wave propagation signatures that can arise from aligned fractures. We are pursuing an integrated study that relates to high-resolution seismic images of natural fractures to the rock parameters that control the storage and mobility of fluids. Our goal is to go beyond the current state-of-the art to develop and demonstrate next generation methodologies for detecting and quantitatively characterizing fracture zones using seismic measurements. Our study incorporates 3 key elements: (1) Theoretical rock physics studies of the anisotropic viscoelastic signatures of fractured rocks, including up scaling analysis and rock-fluid interactions to define the factors relating fractures in the lab and in the field. (2) Modeling of optimal seismic attributes, including offset and azimuth dependence of travel time, amplitude, impedance and spectral signatures of anisotropic fractured rocks. We will quantify the information content of combinations of seismic attributes, and the impact of multi-attribute analyses in reducing uncertainty in fracture interpretations. (3) Integration and interpretation of seismic, well log, and laboratory data, incorporating field geologic fracture characterization and the theoretical results of items 1 and 2 above. The focal point for this project is the demonstration of these methodologies in the Marathon Oil Company Yates Field in West Texas.

  17. Theoretical and laboratory investigations of flow through fractures in crystalline rock

    International Nuclear Information System (INIS)

    Witherspoon, P.A.; Watkins, D.J.; Tsang, Y.W.

    1981-01-01

    A theoretical model developed for flow through a deformable fracture subject to stresses was successfully tested against laboratory experiments. The model contains no arbitrary parameters and can be used to predict flow rates through a single fracture if the fractional fracture contact area can be estimated and if stress-deformation data are available. These data can be obtained from laboratory or in situ tests. The model has considerable potential for practical application. The permeability of ultralarge samples of fractured crystalline rock as a function of stresses was measured. Results from tests on a pervasively fractured 1-m-diameter specimen of granitic rock showed that drastically simplifying assumptions must be used to apply theoretical models to this type of rock mass. Simple models successfully reproduce the trend of reduced permeability as stress is applied in a direction normal to the fracture plane. The tests also demonstrated how fracture conductivity increases as a result of dilatancy associated with shear displacements. The effect of specimen size on the hydraulic properties of fractured rock was also investigated. Permeability tests were performed on specimens of charcoal black granite containing a single fracture subjected to normal stress. Results are presented for tests performed on a 0.914-m-diameter specimen and on the same specimen after it had been reduced to 0.764 m in diameter. The data show that fracture conductivity is sensitive to stress history and sample disturbance

  18. FROMS3D: New Software for 3-D Visualization of Fracture Network System in Fractured Rock Masses

    Science.gov (United States)

    Noh, Y. H.; Um, J. G.; Choi, Y.

    2014-12-01

    A new software (FROMS3D) is presented to visualize fracture network system in 3-D. The software consists of several modules that play roles in management of borehole and field fracture data, fracture network modelling, visualization of fracture geometry in 3-D and calculation and visualization of intersections and equivalent pipes between fractures. Intel Parallel Studio XE 2013, Visual Studio.NET 2010 and the open source VTK library were utilized as development tools to efficiently implement the modules and the graphical user interface of the software. The results have suggested that the developed software is effective in visualizing 3-D fracture network system, and can provide useful information to tackle the engineering geological problems related to strength, deformability and hydraulic behaviors of the fractured rock masses.

  19. Computational Modelling of Fracture Propagation in Rocks Using a Coupled Elastic-Plasticity-Damage Model

    Directory of Open Access Journals (Sweden)

    Isa Kolo

    2016-01-01

    Full Text Available A coupled elastic-plasticity-damage constitutive model, AK Model, is applied to predict fracture propagation in rocks. The quasi-brittle material model captures anisotropic effects and the distinct behavior of rocks in tension and compression. Calibration of the constitutive model is realized using experimental data for Carrara marble. Through the Weibull distribution function, heterogeneity effect is captured by spatially varying the elastic properties of the rock. Favorable comparison between model predictions and experiments for single-flawed specimens reveal that the AK Model is reliable and accurate for modelling fracture propagation in rocks.

  20. Determining the REV for Fracture Rock Mass Based on Seepage Theory

    Directory of Open Access Journals (Sweden)

    Lili Zhang

    2017-01-01

    Full Text Available Seepage problems of the fractured rock mass have always been a heated topic within hydrogeology and engineering geology. The equivalent porous medium model method is the main method in the study of the seepage of the fractured rock mass and its engineering application. The key to the method is to determine a representative elementary volume (REV. The FractureToKarst software, that is, discrete element software, is a main analysis tool in this paper and developed by a number of authors. According to the standard of rock classification established by ISRM, this paper aims to discuss the existence and the size of REV of fractured rock masses with medium tractility and provide a general method to determine the existence of REV. It can be gleaned from the study that the existence condition of fractured rock mass with medium tractility features average fracture spacing smaller than 0.6 m. If average fracture spacing is larger than 0.6 m, there is no existence of REV. The rationality of the model is verified by a case study. The present research provides a method for the simulation of seepage field in fissured rocks.

  1. Effect of rock rheology on fluid leak- off during hydraulic fracturing

    Science.gov (United States)

    Yarushina, V. M.; Bercovici, D.; Oristaglio, M. L.

    2012-04-01

    In this communication, we evaluate the effect of rock rheology on fluid leak­off during hydraulic fracturing of reservoirs. Fluid leak-off in hydraulic fracturing is often nonlinear. The simple linear model developed by Carter (1957) for flow of fracturing fluid into a reservoir has three different regions in the fractured zone: a filter cake on the fracture face, formed by solid additives from the fracturing fluid; a filtrate zone affected by invasion of the fracturing fluid; and a reservoir zone with the original formation fluid. The width of each zone, as well as its permeability and pressure drop, is assumed to remain constant. Physical intuition suggests some straightforward corrections to this classical theory to take into account the pressure dependence of permeability, the compressibility or non-Newtonian rheology of fracturing fluid, and the radial (versus linear) geometry of fluid leak­off from the borehole. All of these refinements, however, still assume that the reservoir rock adjacent to the fracture face is non­deformable. Although the effect of poroelastic stress changes on leak-off is usually thought to be negligible, at the very high fluid pressures used in hydraulic fracturing, where the stresses exceed the rock strength, elastic rheology may not be the best choice. For example, calculations show that perfectly elastic rock formations do not undergo the degree of compaction typically seen in sedimentary basins. Therefore, pseudo-elastic or elastoplastic models are used to fit observed porosity profiles with depth. Starting from balance equations for mass and momentum for fluid and rock, we derive a hydraulic flow equation coupled with a porosity equation describing rock compaction. The result resembles a pressure diffusion equation with the total compressibility being a sum of fluid, rock and pore-space compressibilities. With linear elastic rheology, the bulk formation compressibility is dominated by fluid compressibility. But the possibility

  2. Rock Fracture Toughness Study Under Mixed Mode I/III Loading

    Science.gov (United States)

    Aliha, M. R. M.; Bahmani, A.

    2017-07-01

    Fracture growth in underground rock structures occurs under complex stress states, which typically include the in- and out-of-plane sliding deformation of jointed rock masses before catastrophic failure. However, the lack of a comprehensive theoretical and experimental fracture toughness study for rocks under contributions of out-of plane deformations (i.e. mode III) is one of the shortcomings of this field. Therefore, in this research the mixed mode I/III fracture toughness of a typical rock material is investigated experimentally by means of a novel cracked disc specimen subjected to bend loading. It was shown that the specimen can provide full combinations of modes I and III and consequently a complete set of mixed mode I/III fracture toughness data were determined for the tested marble rock. By moving from pure mode I towards pure mode III, fracture load was increased; however, the corresponding fracture toughness value became smaller. The obtained experimental fracture toughness results were finally predicted using theoretical and empirical fracture models.

  3. a Predictive Model of Permeability for Fractal-Based Rough Rock Fractures during Shear

    Science.gov (United States)

    Huang, Na; Jiang, Yujing; Liu, Richeng; Li, Bo; Zhang, Zhenyu

    This study investigates the roles of fracture roughness, normal stress and shear displacement on the fluid flow characteristics through three-dimensional (3D) self-affine fractal rock fractures, whose surfaces are generated using the modified successive random additions (SRA) algorithm. A series of numerical shear-flow tests under different normal stresses were conducted on rough rock fractures to calculate the evolutions of fracture aperture and permeability. The results show that the rough surfaces of fractal-based fractures can be described using the scaling parameter Hurst exponent (H), in which H = 3 - Df, where Df is the fractal dimension of 3D single fractures. The joint roughness coefficient (JRC) distribution of fracture profiles follows a Gauss function with a negative linear relationship between H and average JRC. The frequency curves of aperture distributions change from sharp to flat with increasing shear displacement, indicating a more anisotropic and heterogeneous flow pattern. Both the mean aperture and permeability of fracture increase with the increment of surface roughness and decrement of normal stress. At the beginning of shear, the permeability increases remarkably and then gradually becomes steady. A predictive model of permeability using the mean mechanical aperture is proposed and the validity is verified by comparisons with the experimental results reported in literature. The proposed model provides a simple method to approximate permeability of fractal-based rough rock fractures during shear using fracture aperture distribution that can be easily obtained from digitized fracture surface information.

  4. Using DC electrical resistivity tomography to quantify preferential flow in fractured rock environments

    CSIR Research Space (South Africa)

    May, F

    2011-09-01

    Full Text Available . This investigation aims to identify preferential flow paths in fractured rock environments. Time-lapse Electrical Resistivity Tomography (TLERT, Lund Imaging System), is regarded as a suitable method for identifying preferential water flow....

  5. Wetted-region structure in horizontal unsaturated fractures: Water entry through the surrounding porous matrix

    International Nuclear Information System (INIS)

    Glass, R.J.; Norton, D.L.

    1991-01-01

    Small-scale processes that influence wetted structure within the plane of a horizontal fracture as the fracture wets or drains through the matrix are investigated. Our approach integrates both aperture-scale modeling and physical experimentation. Several types of aperture-scale models have been defined and implemented. A series of physical experimental systems that allow us to measure wetted-region structure as a function of system parameters and water pressure head in analogue fractures also have been designed. In our preliminary proof-of-concept experiment, hysteresis is clearly evident in the measured saturation/pressure relation, as is the process of air entrapment, which causes a reduction in the connected areas between blocks and the wetted region available for flow in the plane of the fracture. A percolation threshold where the system is quickly spanned, allowing fluid conduction in the fracture plane, is observed which is analogous to that found in the aperture-scale models. A fractal wetted and entrapped-region structure is suggested by both experiment and modeling. This structure implies that flow tortuosity for both flow in the fracture and for inter-block fluid transfer is a scale-dependent function of pressure head

  6. Experimental research on rock fracture failure characteristics under liquid nitrogen cooling conditions

    Science.gov (United States)

    Gao, Feng; Cai, Chengzheng; Yang, Yugui

    2018-06-01

    As liquid nitrogen is injected into a wellbore as fracturing fluid, it can rapidly absorb heat from warmer rock and generate cryogenic condition in downhole region. This will alter the physical conditions of reservoir rocks and further affect rock failure characteristics. To investigate rock fracture failure characteristics under liquid nitrogen cooling conditions, the fracture features of four types of sandstones and one type of marble were tested on original samples (the sample without any treatment) and cryogenic samples (the samples just taken out from the liquid nitrogen), respectively. The differences between original samples and cryogenic samples in load-displacement curves, fracture toughness, energy evolution and the crack density of ruptured samples were compared and analyzed. The results showed that at elastic deformation stage, cryogenic samples presented less plastic deformation and more obvious brittle failure characteristics than original ones. The average fracture toughness of cryogenic samples was 10.47%-158.33% greater than that of original ones, indicating that the mechanical strength of rocks used were enhanced under cooling conditions. When the samples ruptured, the cryogenic ones were required to absorb more energy and reserve more elastic energy. In general, the fracture degree of cryogenic samples was higher than that of original ones. As the samples were entirely fractured, the crack density of cryogenic samples was about 536.67% at most larger than that of original ones. This indicated that under liquid nitrogen cooling conditions, the stimulation reservoir volume is expected to be improved during fracturing. This work could provide a reference to the research on the mechanical properties and fracture failure of rock during liquid nitrogen fracturing.

  7. Analysis of gas migration patterns in fractured coal rocks under actual mining conditions

    Directory of Open Access Journals (Sweden)

    Gao Mingzhong

    2017-01-01

    Full Text Available Fracture fields in coal rocks are the main channels for gas seepage, migration, and extraction. The development, evolution, and spatial distribution of fractures in coal rocks directly affect the permeability of the coal rock as well as gas migration and flow. In this work, the Ji-15-14120 mining face at the No. 8 Coal Mine of Pingdingshan Tian’an Coal Mining Co. Ltd., Pingdingshan, China, was selected as the test site to develop a full-parameter fracture observation instrument and a dynamic fracture observation technique. The acquired video information of fractures in the walls of the boreholes was vectorized and converted to planarly expanded images on a computer-aided design platform. Based on the relative spatial distances between the openings of the boreholes, simultaneous planar images of isolated fractures in the walls of the boreholes along the mining direction were obtained from the boreholes located at various distances from the mining face. Using this information, a 3-D fracture network under mining conditions was established. The gas migration pattern was calculated using a COMSOL computation platform. The results showed that between 10 hours and 1 day the fracture network controlled the gas-flow, rather than the coal seam itself. After one day, the migration of gas was completely controlled by the fractures. The presence of fractures in the overlying rock enables the gas in coal seam to migrate more easily to the surrounding rocks or extraction tunnels situated relatively far away from the coal rock. These conclusions provide an important theoretical basis for gas extraction.

  8. Fracturing Fluid Leak-off for Deep Volcanic Rock in Zhungeer Basin: Mechanism and Control Method

    Directory of Open Access Journals (Sweden)

    Huang Bo

    2017-01-01

    Full Text Available The deep volcanic reservoir in Zhungeer Basin is buried in over 4000m depth, which is characterized by complex lithology (breccia, andesite, basalt, etc., high elastic modulus and massive natural fractures. During hydraulic fracturing, hydraulic fracture will propagate and natural fractures will be triggered by the increasing net pressure. However, the extension of fractures, especially natural fractures, would aggravate the leak-off effect of fracturing fluid, and consequently decrease the fracturing success rate. 4 out of 12 fracturing wells in the field have failed to add enough proppants due to fluid loss. In order to increase the success rate and efficiency of hydraulic fracturing for deep volcanic reservoir, based on theoretical and experimental method, the mechanism of fracturing fluid leak-off is deeply studied. We propose a dualistic proppant scheme and employ the fluid loss reducer to control the fluid leak-off in macro-fractures and micro-fractures respectively. The proposed technique remarkably improved the success rate in deep volcanic rock fracturing. It bears important theoretical value and practical significance to improve the hydraulic fracturing design for deep volcanic reservoir.

  9. The application of positron emission tomography to the study of mass transfer in fractured rock

    International Nuclear Information System (INIS)

    Gilling, D.; Jefferies, N.L.; Fowles, P.; Hawkesworth, M.R.; Parker, D.J.

    1991-06-01

    In order to predict the transport of dissolved radioelements through a fractured rock it is necessary to determine both the geometry of the fracture network and the hydraulic properties of the individual fractures. This paper describes a technique for studying mass transfer in a single fracture. The technique is positron emission tomography (PET) and it offers the potential for visualising quantitatively the migration of dissolved tracers. Preliminary experiments have been undertaken involving the flow of Na-22 and F-18 labelled solutions through artificial fractures. The results demonstrate that PET is well suited to this application. (author)

  10. Experimental and Analytical Research on Fracture Processes in ROck

    Energy Technology Data Exchange (ETDEWEB)

    Herbert H.. Einstein; Jay Miller; Bruno Silva

    2009-02-27

    Experimental studies on fracture propagation and coalescence were conducted which together with previous tests by this group on gypsum and marble, provide information on fracturing. Specifically, different fracture geometries wsere tested, which together with the different material properties will provide the basis for analytical/numerical modeling. INitial steps on the models were made as were initial investigations on the effect of pressurized water on fracture coalescence.

  11. Influence of shear and deviatoric stress on the evolution of permeability in fractured rock

    NARCIS (Netherlands)

    Faoro, Igor; Niemeijer, André; Marone, Chris; Elsworth, Derek

    The evolution of permeability in fractured rock as a function of effective normal stress, shear displacement, and damage remains a complex issue. In this contribution, we report on experiments in which rock surfaces were subject to direct shear under controlled pore pressure and true triaxial stress

  12. Study on flow and mass transport through fractured sedimentary rocks (2)

    International Nuclear Information System (INIS)

    Shimo, Michito; Kumamoto, Sou; Karasaki, Kenzi; Sato, Hisashi; Sawada, Atsushi

    2009-03-01

    It is important for safety assessment of HLW geological disposal to understand hydro-geological conditions at the investigation area, and to evaluate groundwater flow and mass transport model and parameters, at each investigation phase. Traditionally, for Neogene sedimentary rock, the grain spacing of sediments has been considered as the dominant migration path. However, fractures of sedimentary rock could act as dominant paths, although they were soft sedimentary rocks. In this study, as part of developing groundwater flow and mass transport evaluation methodologies of such a fractured sedimentary rock' distributed area, we conducted two different scale of studies; 1) core rock sample scale and 2) several kilometer scale. For the core rock sample scale, some of laboratory hydraulic and tracer experiments have conducted using the rock cores with tailored parallel fracture, obtained at pilot borehole drilled in the vicinity of ventilation shaft. From the test results, hydraulic conductivity, diffusion coefficient, transport aperture, dispersion length and etc. was evaluated. Based on these test results, the influence of these parameters onto mass transport behavior of fractures sedimentary rocks was examined. For larger scale, such as several kilometer scale, the regional scale groundwater flow was examined using temperature data observed along the boreholes at Horonobe site. The results show that the low permeable zone between the boreholes might be estimated. (author)

  13. CAPTURING UNCERTAINTY IN UNSATURATED-ZONE FLOW USING DIFFERENT CONCEPTUAL MODELS OF FRACTURE-MATRIX INTERACTION

    International Nuclear Information System (INIS)

    SUSAN J. ALTMAN, MICHAEL L. WILSON, GUMUNDUR S. BODVARSSON

    1998-01-01

    Preliminary calculations show that the two different conceptual models of fracture-matrix interaction presented here yield different results pertinent to the performance of the potential repository at Yucca Mountain. Namely, each model produces different ranges of flow in the fractures, where radionuclide transport is thought to be most important. This method of using different flow models to capture both conceptual model and parameter uncertainty ensures that flow fields used in TSPA calculations will be reasonably calibrated to the available data while still capturing this uncertainty. This method also allows for the use of three-dimensional flow fields for the TSPA-VA calculations

  14. Matrix diffusion of simple cations, anions, and neutral species in fractured crystalline rocks

    International Nuclear Information System (INIS)

    Sato, Haruo

    1999-01-01

    The diffusion of radionuclides into the pore spaces of a rock matrix and the pore properties in fractured crystalline rocks were studied. The work concentrated on the predominant water-conducting fracture system in the host granodiorite of the Kamaishi In Situ Test Site, which consists of fracture fillings and altered grandodiorite. Through-diffusion experiments to obtain effective and apparent diffusion coefficients (De and Da, respectively) for Na + , Cs + , HTO, Cl - , and SeO 3 2- as a function of ionic charge were conducted through the fracture fillings and altered and intact granodiorite. The total porosity φ, density, pore-size distribution, and specific surface area of the pores of the rocks were also determined by a water saturation method and Hg porosimetry. The average φ is, in the order from highest to lowest, as follows: fracture fillings (5.6%) greater than altered granodiorite (3.2%) greater than intact granodiorite (2.3%), and gradually it decreases into the matrix. The pore sizes of the intact and altered granodiorite range from 10 nm to 200 microm, and the fracture fillings from 50 nm to 200 microm, but almost all pores are found around 0.1 and 200 microm in the fracture fillings. The De values for all species are in the following order: fracture fillings greater than altered granodiorite greater than intact granodiorite, as with the rock porosity. In addition. no effect of ionic charge on De is found. No significant dependence for Da values on the rock porosity is found. The formation factors FF and geometric factors G of the rocks were evaluated by normalizing the free water diffusion coefficient Do for each species. The FF decreased with decreasing rock porosity, and an empirical equation for the rock porosity was derived to be FF = φ 1.57±0.02 . The G values showed a tendency to slightly decrease with decreasing rock porosity, but they were approximately constant (0.12 to 0.19) in this porosity range. This indicates that accessible pores

  15. Characterization on the Fracture system in jurassic granitic rocks: Kosung and Yusung areas

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Kyung Su; Bae, Dae Seok; Kim, Chun Soo; Park, Byung Yoon; Koh, Yong Kweon

    2001-03-01

    The safety of waste disposal can be achieved by a complete isolation of radioactive wastes from biosphere or by a retardation of nuclide migration to reach an acceptable dose level. For the deep geological disposal of high-level radioactive waste, the potential pathways of nuclide primarily depend on the spatial distribution characteristics of conductive fractures in rock mass. Major key issues in the quantification of fracture system for a disposal site are involved in classification criteria, hydraulic parameters, geometry, field investigation methods etc. This research aims to characterize the spatial distribution characteristics of regional lineaments and background fractures in eastern and western-type granite rock mass.

  16. Characterization on the Fracture system in jurassic granitic rocks: Kosung and Yusung areas

    International Nuclear Information System (INIS)

    Kim, Kyung Su; Bae, Dae Seok; Kim, Chun Soo; Park, Byung Yoon; Koh, Yong Kweon

    2001-03-01

    The safety of waste disposal can be achieved by a complete isolation of radioactive wastes from biosphere or by a retardation of nuclide migration to reach an acceptable dose level. For the deep geological disposal of high-level radioactive waste, the potential pathways of nuclide primarily depend on the spatial distribution characteristics of conductive fractures in rock mass. Major key issues in the quantification of fracture system for a disposal site are involved in classification criteria, hydraulic parameters, geometry, field investigation methods etc. This research aims to characterize the spatial distribution characteristics of regional lineaments and background fractures in eastern and western-type granite rock mass

  17. Fracture Characteristics Analysis of Double-layer Rock Plates with Both Ends Fixed Condition

    Directory of Open Access Journals (Sweden)

    S. R. Wang

    2014-07-01

    Full Text Available In order to research on the fracture and instability characteristics of double-layer rock plates with both ends fixed, the three-dimension computational model of double-layer rock plates under the concentrated load was built by using PFC3D technique (three-dimension particle flow code, and the mechanical parameters of the numerical model were determined based on the physical model tests. The results showed the instability process of the double-layer rock plates had four mechanical response phases: the elastic deformation stage, the brittle fracture of upper thick plate arching stage, two rock-arch bearing stage and two rock-arch failure stage; moreover, with the rock plate particle radius from small to large change, the maximum vertical force of double rock-arch appeared when the particle size was a certain value. The maximum vertical force showed an upward trend with the increase of the rock plate temperature, and in the case of the same thickness the maximum vertical force increased with the increase of the upper rock plate thickness. When the boundary conditions of double-layer rock plates changed from the hinged support to the fixed support, the maximum horizontal force observably decreased, and the maximum vertical force showed small fluctuations and then tended towards stability with the increase of cohesive strength of double-layer rock plates.

  18. STAFAN, Fluid Flow, Mechanical Stress in Fractured Rock of Nuclear Waste Repository

    International Nuclear Information System (INIS)

    Huyakorn, P.; Golis, M.J.

    1989-01-01

    1 - Description of program or function: STAFAN (Stress And Flow Analysis) is a two-dimensional, finite-element code designed to model fluid flow and the interaction of fluid pressure and mechanical stresses in a fractured rock surrounding a nuclear waste repository. STAFAN considers flow behavior of a deformable fractured system with fracture-porous matrix interactions, the coupling effects of fluid pressure and mechanical stresses in a medium containing discrete joints, and the inelastic response of the individual joints of the rock mass subject to the combined fluid pressure and mechanical loading. 2 - Restrictions on the complexity of the problem: STAFAN does not presently contain thermal coupling, and it is unable to simulate inelastic deformation of the rock mass and variably saturated or two-phase flow in the fractured porous medium system

  19. Analysis for preliminary evaluation of discrete fracture flow and large-scale permeability in sedimentary rocks

    International Nuclear Information System (INIS)

    Kanehiro, B.Y.; Lai, C.H.; Stow, S.H.

    1987-05-01

    Conceptual models for sedimentary rock settings that could be used in future evaluation and suitability studies are being examined through the DOE Repository Technology Program. One area of concern for the hydrologic aspects of these models is discrete fracture flow analysis as related to the estimation of the size of the representative elementary volume, evaluation of the appropriateness of continuum assumptions and estimation of the large-scale permeabilities of sedimentary rocks. A basis for preliminary analysis of flow in fracture systems of the types that might be expected to occur in low permeability sedimentary rocks is presented. The approach used involves numerical modeling of discrete fracture flow for the configuration of a large-scale hydrologic field test directed at estimation of the size of the representative elementary volume and large-scale permeability. Analysis of fracture data on the basis of this configuration is expected to provide a preliminary indication of the scale at which continuum assumptions can be made

  20. Fracture Initiation of an Inhomogeneous Shale Rock under a Pressurized Supercritical CO2 Jet

    Directory of Open Access Journals (Sweden)

    Yi Hu

    2017-10-01

    Full Text Available Due to the advantages of good fracture performance and the application of carbon capture and storage (CCS, supercritical carbon dioxide (SC-CO2 is considered a promising alternative for hydraulic fracturing. However, the fracture initiation mechanism and its propagation under pressurized SC-CO2 jet are still unknown. To address these problems, a fluid–structure interaction (FSI-based numerical simulation model along with a user-defined code was used to investigate the fracture initiation in an inhomogeneous shale rock. The mechanism of fracturing under the effect of SC-CO2 jet was explored, and the effects of various influencing factors were analyzed and discussed. The results indicated that higher velocity jets of SC-CO2 not only caused hydraulic-fracturing ring, but also resulted in the increase of stress in the shale rock. It was found that, with the increase of perforation pressure, more cracks initiated at the tip. In contrast, the length of cracks at the root decreased. The length-to-diameter ratio and the aperture ratio distinctly affected the pressurization of SC-CO2 jet, and contributed to the non-linear distribution and various maximum values of the stress in shale rock. The results proved that Weibull probability distribution was appropriate for analysis of the fracture initiation. The studied parameters explain the distribution of weak elements, and they affect the stress field in shale rock.

  1. Upscaling permeability for three-dimensional fractured porous rocks with the multiple boundary method

    Science.gov (United States)

    Chen, Tao; Clauser, Christoph; Marquart, Gabriele; Willbrand, Karen; Hiller, Thomas

    2018-02-01

    Upscaling permeability of grid blocks is crucial for groundwater models. A novel upscaling method for three-dimensional fractured porous rocks is presented. The objective of the study was to compare this method with the commonly used Oda upscaling method and the volume averaging method. First, the multiple boundary method and its computational framework were defined for three-dimensional stochastic fracture networks. Then, the different upscaling methods were compared for a set of rotated fractures, for tortuous fractures, and for two discrete fracture networks. The results computed by the multiple boundary method are comparable with those of the other two methods and fit best the analytical solution for a set of rotated fractures. The errors in flow rate of the equivalent fracture model decrease when using the multiple boundary method. Furthermore, the errors of the equivalent fracture models increase from well-connected fracture networks to poorly connected ones. Finally, the diagonal components of the equivalent permeability tensors tend to follow a normal or log-normal distribution for the well-connected fracture network model with infinite fracture size. By contrast, they exhibit a power-law distribution for the poorly connected fracture network with multiple scale fractures. The study demonstrates the accuracy and the flexibility of the multiple boundary upscaling concept. This makes it attractive for being incorporated into any existing flow-based upscaling procedures, which helps in reducing the uncertainty of groundwater models.

  2. FTRANS, Radionuclide Flow in Groundwater and Fractured Rock

    International Nuclear Information System (INIS)

    Huyakorn, P.; Golis, M.J.

    1987-01-01

    1 - Description of program or function: FTRANS (Fractured flow and Transport of Radionuclides) is a two-dimensional finite-element code designed to simulate ground-water flow and transport of radioactive nuclides in a fractured porous return medium. FTRANS takes into account fluid interactions between the fractures and porous matrix blocks, advective-dispersive transport in the fractures and diffusion in the porous matrix blocks, and chain reactions of radionuclide components. It has the capability to model the fractured system using either the dual-porosity or the discrete- fracture modeling approach or a combination of both. FTRANS can be used to perform two-dimensional near-field or far-field predictive analyses of ground-water flow and to perform risk assessments of radionuclide transport from nuclear waste repository subsystems to the biosphere. 2 - Restrictions on the complexity of the problem: Although FTRANS does cannot account for deformation processes which can affect the flow capacity and velocity field

  3. Characterising rock fracture aperture-spacing relationships using power-law relationships: some considerations

    Science.gov (United States)

    Brook, Martin; Hebblewhite, Bruce; Mitra, Rudrajit

    2016-04-01

    The size-scaling of rock fractures is a well-studied problem in geology, especially for permeability quantification. The intensity of fractures may control the economic exploitation of fractured reservoirs because fracture intensity describes the abundance of fractures potentially available for fluid flow. Moreover, in geotechnical engineering, fractures are important for parameterisation of stress models and excavation design. As fracture data is often collected from widely-spaced boreholes where core recovery is often incomplete, accurate interpretation and representation of fracture aperture-frequency relationships from sparse datasets is important. Fracture intensity is the number of fractures encountered per unit length along a sample scanline oriented perpendicular to the fractures in a set. Cumulative frequency of fractures (F) is commonly related to fracture aperture (A) in the form of a power-law (F = aA-b), with variations in the size of the a coefficient between sites interpreted to equate to fracture frequency for a given aperture (A). However, a common flaw in this approach is that even a small change in b can have a large effect on the response of the fracture frequency (F) parameter. We compare fracture data from the Late Permian Rangal Coal Measures from Australia's Bowen Basin, with fracture data from Jurassic carbonates from the Sierra Madre Oriental, northeastern Mexico. Both power-law coefficient a and exponent b control the fracture aperture-frequency relationship in conjunction with each other; that is, power-laws with relatively low a coefficients have relatively high b exponents and vice versa. Hence, any comparison of different power-laws must take both a and b into consideration. The corollary is that different sedimentary beds in the Sierra Madre carbonates do not show ˜8× the fracture frequency for a given fracture aperture, as based solely on the comparison of coefficient a. Rather, power-law "sensitivity factors" developed from both

  4. Evaluation of Fractured Basement Complex Rock Porosity by ...

    African Journals Online (AJOL)

    current resistivity sounding as complementary geophysical technique to Schlumberger vertical electrical sounding in characterizing fractured geologic systems. Previously, Schlumberger vertical electrical sounding was used to collect data.

  5. The effect of offset on fracture permeability of rocks from the Southern Andes Volcanic Zone, Chile

    Science.gov (United States)

    Pérez-Flores, P.; Wang, G.; Mitchell, T. M.; Meredith, P. G.; Nara, Y.; Sarkar, V.; Cembrano, J.

    2017-11-01

    The Southern Andes Volcanic Zone (SVZ) represents one of the largest undeveloped geothermal provinces in the world. Development of the geothermal potential requires a detailed understanding of fluid transport properties of its main lithologies. The permeability of SVZ rocks is altered by the presence of fracture damage zones produced by the Liquiñe-Ofqui Fault System (LOFS) and the Andean Transverse Faults (ATF). We have therefore measured the permeability of four representative lithologies from the volcanic basement in this area: crystalline tuff, andesitic dike, altered andesite and granodiorite. For comparative purposes, we have also measured the permeability of samples of Seljadalur basalt, an Icelandic rock with widely studied and reported hydraulic properties. Specifically, we present the results of a systematic study of the effect of fractures and fracture offsets on permeability as a function of increasing effective pressure. Baseline measurements on intact samples of SVZ rocks show that the granodiorite has a permeability (10-18 m2), two orders of magnitude higher than that of the volcanic rocks (10-20 m2). The presence of throughgoing mated macro-fractures increases permeability by between four and six orders of magnitude, with the highest permeability recorded for the crystalline tuff. Increasing fracture offset to produce unmated fractures results in large increases in permeability up to some characteristic value of offset, beyond which permeability changes only marginally. The increase in permeability with offset appears to depend on fracture roughness and aperture, and these are different for each lithology. Overall, fractured SVZ rocks with finite offsets record permeability values consistent with those commonly found in geothermal reservoirs (>10-16 m2), which potentially allow convective/advective flow to develop. Hence, our results demonstrate that the fracture damage zones developed within the SVZ produce permeable regions, especially within the

  6. Fracture toughness properties of rocks in Olkiluoto: Laboratory measurements 2008-2009

    Energy Technology Data Exchange (ETDEWEB)

    Siren, T.

    2012-05-15

    In Olkiluoto an underground rock characterization facility (ONKALO) for the final disposal site of spent nuclear fuel has been under thorough research many years, but further knowledge is needed on fracture toughness parameters. Fracture toughness parameters are important for example in fracture mechanics prediction for Posiva's Olkiluoto Spalling Experiment (POSE). This working report describes a laboratory campaign that was done between 2008 and 2009. The campaign aimed at determining the fracture mechanics parameters as well as density and ultrasonic velocities for Olkiluoto rocks. The specimens delivered were selected by Posiva; the core showed no damage and the quality of the delivered cores was good with varying sample diameter. Most of the test samples (9 out of 12) are gneissic rock. The Mode I fracture toughness was determined using two different methods to account for two different fracturing directions. The methods are the Chevron Bend (CB) test as proposed in the ISRM Suggested Method and a method based on the Brazilian Disk (BD) experiment. The Mode II fracture toughness was determined using the Punch-Through Shear with Confining Pressure experiment on the remaining pieces from the CB testing. The scatter in the results is very large, even within one piece of core sample. Usually the scatter of results is less than 5 %. The high scatter in the data at hand is believed to be due to the very inhomogeneous nature of the rock material. The magnitude of the determined Mode I fracture toughness compares well with available reported data for medium to coarse grained granitoide rocks. However the scatter of the mode II fracture toughness values is higher than experienced on other rock types, but the variability is reasonable for the inhomogeneous rock type. Distinguishing the fracture toughness values for different anisotropy directions would require more thorough testing with quality samples at different anisotropy directions. However since fracture

  7. Alternative conceptual models and codes for unsaturated flow in fractured tuff: Preliminary assessments for GWTT-95

    International Nuclear Information System (INIS)

    Ho, C.K.; Altman, S.J.; Arnold, B.W.

    1995-09-01

    Groundwater travel time (GWTT) calculations will play an important role in addressing site-suitability criteria for the potential high-level nuclear waste repository at Yucca Mountain,Nevada. In support of these calculations, Preliminary assessments of the candidate codes and models are presented in this report. A series of benchmark studies have been designed to address important aspects of modeling flow through fractured media representative of flow at Yucca Mountain. Three codes (DUAL, FEHMN, and TOUGH 2) are compared in these benchmark studies. DUAL is a single-phase, isothermal, two-dimensional flow simulator based on the dual mixed finite element method. FEHMN is a nonisothermal, multiphase, multidimensional simulator based primarily on the finite element method. TOUGH2 is anon isothermal, multiphase, multidimensional simulator based on the integral finite difference method. Alternative conceptual models of fracture flow consisting of the equivalent continuum model (ECM) and the dual permeability (DK) model are used in the different codes

  8. Determination of rock fracture parameters from crack models for failure in compression

    International Nuclear Information System (INIS)

    Kemeny, J.M.; Cook, N.G.W.

    1987-01-01

    Micromechanical models for axial splitting and for shear faulting are used to investigate parameters associated with rock fracture under compressive stresses. The fracture energies to create splitting fractures and shear faults are calculated using laboratory triaxial data. These energies are compared with the fracture energies for the propagation of microcracks that coalesce to form the larger scale fractures. It is found that for Westerly granite, the energies to create splitting fractures and shear faults are about three orders of magnitude greater than the energy needed to drive the tensile microcracks, due to the large amount of subsidiary crack surface area created in forming the larger scale fractures. A similar scale effect can be expected when extrapolating the laboratory results to field scale problems

  9. Study of the fracture behavior of mortar and concretes with crushed rock or pebble aggregates

    Directory of Open Access Journals (Sweden)

    Sebastião Ribeiro

    2011-03-01

    Full Text Available The objective of this work was to compare the fracture energy of mortar and concretes produced with crushed rock and pebble aggregates using zero, 10, 20, 30 and 40% of aggregates mixed with standard mortar and applying the wedge splitting method to achieve stable crack propagation. The samples were cast in a special mold and cured for 28 days, after which they were subjected to crack propagation tests by the wedge splitting method to determine the fracture energies of the mortar and concrete. The concretes showed higher fracture energy than the mortar, and the concretes containing crushed rock showed higher resistance to crack propagation than all the compositions containing pebbles. The fracture energy varied from 38 to 55 J.m-2. A comparison of the number of aggregates that separated from the two concrete matrices with the highest fracture energies indicated that the concrete containing pebbles crumbled more easily and was therefore less resistant to crack propagation.

  10. SIMPLE ANALYTICAL MODEL FOR HEAT FLOW IN FRACTURES - APPLICATION TO STEAM ENHANCED REMEDIATION CONDUCTED IN FRACTURED ROCK

    Science.gov (United States)

    Remediation of fractured rock sites contaminated by non-aqueous phase liquids has long been recognized as the most difficult undertaking of any site clean-up. Recent pilot studies conducted at the Edwards Air Force Base in California and the former Loring Air Force Base in Maine ...

  11. Discrete fracture modelling of the Finnsjoen rock mass: Phase 2

    International Nuclear Information System (INIS)

    Geier, J.E.; Axelsson, C.L.; Haessler, L.; Benabderrahmane, A.

    1992-04-01

    A discrete fracture network (DFN) model of the Finnsjoen site was derived from field data, and used to predict block-scale flow and transport properties. The DFN model was based on a compound Poisson process, with stochastic fracture zones, and individual fracture concentrated around the fracture zones. This formulation was used to represent the multitude of fracture zones at the site which could be observed on lineament maps and in boreholes, but were not the focus of detailed characterization efforts. Due to a shortage of data for fracture geometry at depth, distributions of fracture orientation and size were assumed to be uniform throughout the site. Transmissivity within individual fracture planes was assumed to vary according to a fractal model. Constant-head packer tests were simulated with the model, and the observed transient responses were compared with actual tests in terms of distributions of interpreted transmissivity and flow dimension, to partially validate the model. Both simulated and actual tests showed a range of flow dimension from sublinear to spherical, indicating local variations in the connectivity of the fracture population. A methodology was developed for estimation of an effective stochastic continuum from the DFN model, but this was only partly demonstrated. Directional conductivities for 40 m block were estimated using the DFN model. These show extremely poor correlation with results of multiple packer tests in the same blocks, indicating possible limitation of small-scale packer tests for predicting block-scale properties. Estimates are given of effective flow porosity and flow wetted surface, based on the block-scale flow fields calculated by the DFN model, and probabilistic models for the relationships among local fracture transmissivity, void space, and specific surface. The database for constructing these models is extremely limited. A review is given of the existing database for single fracture hydrologic properties. (127 refs

  12. Subcritical fracture propagation in rocks: An examination using the methods of fracture mechanics and non-destructive testing. Ph.D. Thesis

    Science.gov (United States)

    Swanson, P. L.

    1984-01-01

    An experimental investigation of tensile rock fracture is presented with an emphasis on characterizing time dependent crack growth using the methods of fracture mechanics. Subcritical fracture experiments were performed in moist air on glass and five different rock types at crack velocities using the double torsion technique. The experimental results suggest that subcritical fracture resistance in polycrystals is dominated by microstructural effects. Evidence for gross violations of the assumptions of linear elastic fracture mechanics and double torsion theory was found in the tests on rocks. In an effort to obtain a better understanding of the physical breakdown processes associated with rock fracture, a series of nondestructive evaluation tests were performed during subcritical fracture experiments on glass and granite. Comparison of the observed process zone shape with that expected on the basis of a critical normal principal tensile stress criterion shows that the zone is much more elongated in the crack propagation direction than predicted by the continuum based microcracking model alone.

  13. Colloid-Facilitated Transport of Cations in an Unsaturated Fractured Soil Under Transient Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Ryan, Joseph [Univ. of Colorado, Boulder, CO (United States)

    2015-01-31

    Rainfall experiments were conducted using intact soil cores and an instrumented soil pedon to examine the effect of physical heterogeneity and rainfall characteristics on the mobilization of colloids, organic matter, cesium, and strontium in a fractured soil. To measure the spatial variability of infiltration of colloids and contaminants, samples were collected through a 19-port grid placed below the soil core in laboratory study and in 27 samplers at multiple depths in the soil pedon in the field study. Cesium and strontium were applied to the soil cores and the soil pedon prior to mobilization experiments. Rainwater solutions of multiple ionic strengths and organic matter concentrations were applied to the soil cores and soil pedon to mobilize in situ colloids, cesium, and strontium. The mobilization of colloids and metal cations occurred through preferential flow paths in the soil cores. Compared to steady rainfall, greater amounts of colloids were mobilized during rainfall interrupted by pauses, which indicates that the supply of colloids to be mobilized was replenished during the pauses. A maximum in the amount of mobilized colloids were mobilized during a rainfall following a pause of 2.5 d. Pauses of shorter or longer duration resulted in less colloid mobilization. Freeze-thaw cycles, a transient condition in winter, enhanced colloid mobilization and colloid-facilitated transport of cesium and strontium in the soil cores. The exchange of solutes between the soil matrix and macropores caused a hysteretic mobilization of colloids, cesium, and strontium during changes in ionic strength. Colloid-facilitated mobilization of cesium and strontium was important at low ionic strength in fractures where slow flow allowed greater exchange of flow between the fractures and the surrounding matrix. The release of cesium and strontium by cation exchange occurred at high ionic strength in fractures where there is a little exchange of pore water with the surrounding matrix

  14. Summary of air permeability data from single-hole injection tests in unsaturated fractured tuffs at the Apache Leap Research Site: Results of steady-state test interpretation

    International Nuclear Information System (INIS)

    Guzman, A.G.; Geddis, A.M.; Henrich, M.J.; Lohrstorfer, C.F.; Neuman, S.P.

    1996-03-01

    This document summarizes air permeability estimates obtained from single hole pneumatic injection tests in unsaturated fractured tuffs at the Covered Borehole Site (CBS) within the larger apache Leap Research Site (ALRS). Only permeability estimates obtained from a steady state interpretation of relatively stable pressure and flow rate data are included. Tests were conducted in five boreholes inclined at 45 degree to the horizontal, and one vertical borehole. Over 180 borehole segments were tested by setting the packers 1 m apart. Additional tests were conducted in segments of lengths 0.5, 2.0, and 3.0 m in one borehole, and 2.0 m in another borehole, bringing the total number of tests to over 270. Tests were conducted by maintaining a constant injection rate until air pressure became relatively stable and remained so for some time. The injection rate was then incremented by a constant value and the procedure repeated. The air injection rate, pressure, temperature, and relative humidity were recorded. For each relatively stable period of injection rate and pressure, air permeability was estimated by treating the rock around each test interval as a uniform, isotropic porous medium within which air flows as a single phase under steady state, in a pressure field exhibiting prolate spheroidal symmetry. For each permeability estimate the authors list the corresponding injection rate, pressure, temperature and relative humidity. They also present selected graphs which show how the latter quantities vary with time; logarithmic plots of pressure versus time which demonstrate the importance of borehole storage effects during the early transient portion of each incremental test period; and semilogarithmic plots of pressure versus recovery time at the end of each test sequence

  15. Reaction-Infiltration Instabilities in Fractured and Porous Rocks

    Energy Technology Data Exchange (ETDEWEB)

    Ladd, Anthony [Univ. of Florida, Gainesville, FL (United States)

    2017-09-19

    In this project we are developing a multiscale analysis of the evolution of fracture permeability, using numerical simulations and linear stability analysis. Our simulations include fully three-dimensional simulations of the fracture topography, fluid flow, and reactant transport, two-dimensional simulations based on aperture models, and linear stability analysis.

  16. Complex Contact Angles Calculated from Capillary Rise Measurements on Rock Fracture Faces

    Science.gov (United States)

    Perfect, E.; Gates, C. H.; Brabazon, J. W.; Santodonato, L. J.; Dhiman, I.; Bilheux, H.; Bilheux, J. C.; Lokitz, B. S.

    2017-12-01

    Contact angles for fluids in unconventional reservoir rocks are needed for modeling hydraulic fracturing leakoff and subsequent oil and gas extraction. Contact angle measurements for wetting fluids on rocks are normally performed using polished flat surfaces. However, such prepared surfaces are not representative of natural rock fracture faces, which have been shown to be rough over multiple scales. We applied a variant of the Wilhelmy plate method for determining contact angle from the height of capillary rise on a vertical surface to the wetting of rock fracture faces by water in the presence of air. Cylindrical core samples (5.05 cm long x 2.54 cm diameter) of Mancos shale and 6 other rock types were investigated. Mode I fractures were created within the cores using the Brazilian method. Each fractured core was then separated into halves exposing the fracture faces. One fracture face from each rock type was oriented parallel to a collimated neutron beam in the CG-1D imaging instrument at ORNL's High Flux Isotope Reactor. Neutron radiography was performed using the multi-channel plate detector with a spatial resolution of 50 μm. Images were acquired every 60 s after a water reservoir contacted the base of the fracture face. The images were normalized to the initial dry condition so that the upward movement of water on the fracture face was clearly visible. The height of wetting at equilibrium was measured on the normalized images using ImageJ. Contact angles were also measured on polished flat surfaces using the conventional sessile drop method. Equilibrium capillary rise on the exposed fracture faces was up to 8.5 times greater than that predicted for polished flat surfaces from the sessile drop measurements. These results indicate that rock fracture faces are hyperhydrophilic (i.e., the height of capillary rise is greater than that predicted for a contact angle of zero degrees). The use of complex numbers permitted calculation of imaginary contact angles for

  17. Experimental Study and Numerical Modeling of Fracture Propagation in Shale Rocks During Brazilian Disk Test

    Science.gov (United States)

    Mousavi Nezhad, Mohaddeseh; Fisher, Quentin J.; Gironacci, Elia; Rezania, Mohammad

    2018-06-01

    Reliable prediction of fracture process in shale-gas rocks remains one of the most significant challenges for establishing sustained economic oil and gas production. This paper presents a modeling framework for simulation of crack propagation in heterogeneous shale rocks. The framework is on the basis of a variational approach, consistent with Griffith's theory. The modeling framework is used to reproduce the fracture propagation process in shale rock samples under standard Brazilian disk test conditions. Data collected from the experiments are employed to determine the testing specimens' tensile strength and fracture toughness. To incorporate the effects of shale formation heterogeneity in the simulation of crack paths, fracture properties of the specimens are defined as spatially random fields. A computational strategy on the basis of stochastic finite element theory is developed that allows to incorporate the effects of heterogeneity of shale rocks on the fracture evolution. A parametric study has been carried out to better understand how anisotropy and heterogeneity of the mechanical properties affect both direction of cracks and rock strength.

  18. A Review of Critical Conditions for the Onset of Nonlinear Fluid Flow in Rock Fractures

    Directory of Open Access Journals (Sweden)

    Liyuan Yu

    2017-01-01

    Full Text Available Selecting appropriate governing equations for fluid flow in fractured rock masses is of special importance for estimating the permeability of rock fracture networks. When the flow velocity is small, the flow is in the linear regime and obeys the cubic law, whereas when the flow velocity is large, the flow is in the nonlinear regime and should be simulated by solving the complex Navier-Stokes equations. The critical conditions such as critical Reynolds number and critical hydraulic gradient are commonly defined in the previous works to quantify the onset of nonlinear fluid flow. This study reviews the simplifications of governing equations from the Navier-Stokes equations, Stokes equation, and Reynold equation to the cubic law and reviews the evolutions of critical Reynolds number and critical hydraulic gradient for fluid flow in rock fractures and fracture networks, considering the influences of shear displacement, normal stress and/or confining pressure, fracture surface roughness, aperture, and number of intersections. This review provides a reference for the engineers and hydrogeologists especially the beginners to thoroughly understand the nonlinear flow regimes/mechanisms within complex fractured rock masses.

  19. Polyaxial stress-dependent permeability of a three-dimensional fractured rock layer

    Science.gov (United States)

    Lei, Qinghua; Wang, Xiaoguang; Xiang, Jiansheng; Latham, John-Paul

    2017-12-01

    A study about the influence of polyaxial (true-triaxial) stresses on the permeability of a three-dimensional (3D) fractured rock layer is presented. The 3D fracture system is constructed by extruding a two-dimensional (2D) outcrop pattern of a limestone bed that exhibits a ladder structure consisting of a "through-going" joint set abutted by later-stage short fractures. Geomechanical behaviour of the 3D fractured rock in response to in-situ stresses is modelled by the finite-discrete element method, which can capture the deformation of matrix blocks, variation of stress fields, reactivation of pre-existing rough fractures and propagation of new cracks. A series of numerical simulations is designed to load the fractured rock using various polyaxial in-situ stresses and the stress-dependent flow properties are further calculated. The fractured layer tends to exhibit stronger flow localisation and higher equivalent permeability as the far-field stress ratio is increased and the stress field is rotated such that fractures are preferentially oriented for shearing. The shear dilation of pre-existing fractures has dominant effects on flow localisation in the system, while the propagation of new fractures has minor impacts. The role of the overburden stress suggests that the conventional 2D analysis that neglects the effect of the out-of-plane stress (perpendicular to the bedding interface) may provide indicative approximations but not fully capture the polyaxial stress-dependent fracture network behaviour. The results of this study have important implications for understanding the heterogeneous flow of geological fluids (e.g. groundwater, petroleum) in subsurface and upscaling permeability for large-scale assessments.

  20. Isotope techniques in the study of the hydrology of fractured and fissured rocks

    International Nuclear Information System (INIS)

    1989-01-01

    It is generally agreed that the hydrology of fractured rocks refers to the occurrence and movement of groundwater in rocks whose porosity is due to cracks, fissures and fractures in compact rocks. Until recently, crystalline rocks were considered to be impervious (the role of karst reservoirs for groundwater storage is already known). Thus, although fractured rocks cover approximately one-third of the Earth's surface, knowledge of groundwater flow dynamics still needs to be substantively improved. The Proceedings include the papers presented at the Advisory Group Meeting on the Application of Isotope Techniques in the Study of the Hydrology of Fractured and Fissured Rocks, which took place in Vienna from 17 to 21 November 1986. The meeting was attended by 21 scientists from 10 Member States. The Group agreed that the following topics should be given the highest priority: (1) Protection of groundwater resources should be incorporated into all future activities. This implies that recharge areas have to be delineated, not only using nuclear techniques but also other hydrogeological and geochemical methods. Research efforts in this direction should be intensified. (2) The Group was aware that new isotope techniques are being developed in hydrogeology and agreed that their application in fractured and fissured rocks showed promise. It was therefore suggested that information on new isotopes such as 36 Cl and 129 I should be gathered, either in the form of the various techniques currently being used by different laboratories or through the various activities that are being undertaken. Ways of co-ordinating the work being done and exchanging information at the international level should be encouraged. The Proceedings should be of interest to scientists responsible for the evaluation of water resources in crystalline rocks. It is hoped that hydrologists and hydrogeologists working in such terrains who are not familiar with the use of isotope techniques will find ideas and

  1. Hydrogeomechanics for rock engineering: coupling subsurface hydrogeomechanical assessement and hydrogeotechnical mapping on fracturated rock masses

    OpenAIRE

    Meirinhos, João Miguel de Freitas

    2015-01-01

    The present work aims to achieve and further develop a hydrogeomechanical approach in Caldas da Cavaca hydromineral system rock mass (Aguiar da Beira, NW Portugal), and contribute to a better understanding of the hydrogeological conceptual site model. A collection of several data, namely geology, hydrogeology, rock and soil geotechnics, borehole hydraulics and hydrogeomechanics, was retrieved from three rock slopes (Lagoa, Amores and Cancela). To accomplish a comprehensive analysis and rock e...

  2. Modelling of flow and contaminant migration in single rock fractures

    International Nuclear Information System (INIS)

    Dahlblom, P.; Joensson, L.

    1990-03-01

    The report deals with flow and hydrodynamic dispersion of a nonreactive contaminant in a single, irregularly shaped fracture. The main purpose of the report is to describe the basis and development of a computational 'tool' for simulating the aperture geometry of a single fracture and the detailed flow in it. On the basis of this flow information further properties of the fracture can be studied. Some initial application to dispersion of a nonreactive contaminant are thus discussed. The spatial pattern of variation of the fracture aperture is considered as a two-dimensional stochastic process. A method for simulation of such a process is described. The stochastic properties can be chosen arbitrarily. It is assumed that the fracture aperture belongs to a log-normal distribution. For calculation of the flow pattern, the Navier-Stokes equations are simplified to describe low velocity and steady-state flow. These equations, and the continuity equation are integrated in the direction across the fracture plane. A stream function, which describes the integrated flow in the fracture, is defined. A second order partial differential equation, with respect to the stream function, is established and solved by the finite difference method. Isolines for the stream function define boundaries between channels with equal flow rates. The travel time for each channel can be calculated to achieve a measure of the dispersion. The impact of the aperture distribution on the ratio between the mass balance fracture aperture and the cubic law fracture aperture is shown by simple examples. (28 figs., 1 tab., 22 refs.)

  3. The Role of the Rock on Hydraulic Fracturing of Tight Shales

    Science.gov (United States)

    Suarez-Rivera, R.; Green, S.; Stanchits, S.; Yang, Y.

    2011-12-01

    Successful economic production of oil and gas from nano-darcy-range permeability, tight shale reservoirs, is achieved via massive hydraulic fracturing. This is so despite their limited hydrocarbon in place, on per unit rock volume basis. As a reference, consider a typical average porosity of 6% and an average hydrocarbon saturation of 50% to 75%. The importance of tight shales results from their large areal extent and vertical thickness. For example, the areal extent of the Anwar field in Saudi Arabia of 3230 square miles (and 300 ft thick), while the Marcellus shale alone is over 100,000 square miles (and 70 to 150 ft thick). The low permeability of the rock matrix, the predominantly mineralized rock fabric, and the high capillary forces to both brines and hydrocarbons, restrict the mobility of pore fluids in these reservoirs. Thus, one anticipates that fluids do not move very far within tight shales. Successful production, therefore results from maximizing the surface area of contact with the reservoir by massive hydraulic fracturing from horizontal bore holes. This was the conceptual breakthrough of the previous decade and the one that triggered the emergence of gas shales, and recently oily shales, as important economic sources of energy. It is now understood that the process can be made substantially more efficient, more sustainable, and more cost effective by understanding the rock. This will be the breakthrough of this decade. Microseismic monitoring, mass balance calculations, and laboratory experiments of hydraulic fracturing on tight shales indicate the development of fracture complexity and fracture propagation that can not be explained in detail in this layered heterogeneous media. It is now clear that in tight shales the large-scale formation fabric is responsible for fracture complexity. For example, the presence and pervasiveness of mineralized fractures, bed interfaces, lithologic contacts, and other types of discontinuities, and their orientation

  4. Time dependent fracture growth in intact crystalline rock: new laboratory procedures

    International Nuclear Information System (INIS)

    Backers, T.; Stephansson, O.

    2008-01-01

    Short term laboratory tests to determine the strength of rock material are commonly used to assess stability of rock excavations. However, loading the rock below its short term strength may lead to delayed failure due to slow stable fracture growth. This time-dependent phenomenon is called subcritical fracture growth. A fracture mechanics based approach is applied in this study to determine the parameters describing subcritical fracture growth under Mode Ⅰ (tensile) and Mode Ⅱ (in-plane shear) loading in terms of the stress intensity factors of saturated granodiorite from the) Aespoe HRL. A statistical method is applied to data from three-point bending (tension) and Punch-Through Shear with Confining Pressure, PTS/CP, (shear) experiments. One population of each set-up was subjected to rapid loading tests yielding a strength probability distribution. A second population was loaded up to a certain fraction of the statistical percentage for failure and the time-to-failure was determined. From these two populations the subcritical fracture growth parameters were determined successfully. Earlier studies demonstrated subcritical fracture growth under Mode I loading conditions, but this study shows that under a Mode Ⅱ load time-dependent fracture growth exists as well. (authors)

  5. Unified pipe network method for simulation of water flow in fractured porous rock

    Science.gov (United States)

    Ren, Feng; Ma, Guowei; Wang, Yang; Li, Tuo; Zhu, Hehua

    2017-04-01

    Rock masses are often conceptualized as dual-permeability media containing fractures or fracture networks with high permeability and porous matrix that is less permeable. In order to overcome the difficulties in simulating fluid flow in a highly discontinuous dual-permeability medium, an effective unified pipe network method is developed, which discretizes the dual-permeability rock mass into a virtual pipe network system. It includes fracture pipe networks and matrix pipe networks. They are constructed separately based on equivalent flow models in a representative area or volume by taking the advantage of the orthogonality of the mesh partition. Numerical examples of fluid flow in 2-D and 3-D domain including porous media and fractured porous media are presented to demonstrate the accuracy, robustness, and effectiveness of the proposed unified pipe network method. Results show that the developed method has good performance even with highly distorted mesh. Water recharge into the fractured rock mass with complex fracture network is studied. It has been found in this case that the effect of aperture change on the water recharge rate is more significant in the early stage compared to the fracture density change.

  6. Microseismic Analysis of Fracture of an Intact Rock Asperity Traversing a Sawcut Fault

    Science.gov (United States)

    Mclaskey, G.; Lockner, D. A.

    2017-12-01

    Microseismic events carry information related to stress state, fault geometry, and other subsurface properties, but their relationship to large and potentially damaging earthquakes is not well defined. We conducted laboratory rock mechanics experiments that highlight the interaction between a sawcut fault and an asperity composed of an intact rock "pin". The sample is a 76 mm diameter cylinder of Westerly granite with a 21 mm diameter cylinder (the pin) of intact Westerly granite that crosses the sawcut fault. Upon loading to 80 MPa in a triaxial machine, we first observed a slip event that ruptured the sawcut fault, slipped about 35 mm, but was halted by the rock pin. With continued loading, the rock pin failed in a swarm of thousands of M -7 seismic events similar to the localized microcracking that occurs during the final fracture nucleation phase in an intact rock sample. Once the pin was fractured to a critical point, it permitted complete rupture events on the sawcut fault (stick-slip instabilities). No seismicity was detected on the sawcut fault plane until the pin was sheared. Subsequent slip events were preceded by 10s of foreshocks, all located on the fault plane. We also identified an aseismic zone on the fault plane surrounding the fractured rock pin. A post-mortem analysis of the sample showed a thick gouge layer where the pin intersected the fault, suggesting that this gouge propped open the fault and prevented microseismic events in its vicinity. This experiment is an excellent case study in microseismicity since the events separate neatly into three categories: slip on the sawcut fault, fracture of the intact rock pin, and off-fault seismicity associated with pin-related rock joints. The distinct locations, timing, and focal mechanisms of the different categories of microseismic events allow us to study how their occurrence is related to the mechanics of the deforming rock.

  7. Multi-Attribute Seismic/Rock Physics Approach to Characterizing Fractured Reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Gary Mavko

    2004-11-30

    Most current seismic methods to seismically characterize fractures in tight reservoirs depend on a few anisotropic wave propagation signatures that can arise from aligned fractures. While seismic anisotropy can be a powerful fracture diagnostic, a number of situations can lessen its usefulness or introduce interpretation ambiguities. Fortunately, laboratory and theoretical work in rock physics indicates that a much broader spectrum of fracture seismic signatures can occur, including a decrease in P- and S-wave velocities, a change in Poisson's ratio, an increase in velocity dispersion and wave attenuation, as well as well as indirect images of structural features that can control fracture occurrence. The goal of this project was to demonstrate a practical interpretation and integration strategy for detecting and characterizing natural fractures in rocks. The approach was to exploit as many sources of information as possible, and to use the principles of rock physics as the link among seismic, geologic, and log data. Since no single seismic attribute is a reliable fracture indicator in all situations, the focus was to develop a quantitative scheme for integrating the diverse sources of information. The integrated study incorporated three key elements: The first element was establishing prior constraints on fracture occurrence, based on laboratory data, previous field observations, and geologic patterns of fracturing. The geologic aspects include analysis of the stratigraphic, structural, and tectonic environments of the field sites. Field observations and geomechanical analysis indicates that fractures tend to occur in the more brittle facies, for example, in tight sands and carbonates. In contrast, strain in shale is more likely to be accommodated by ductile flow. Hence, prior knowledge of bed thickness and facies architecture, calibrated to outcrops, are powerful constraints on the interpreted fracture distribution. Another important constraint is that

  8. Rock Fractures and Fluid Flow: Contemporary Understanding and Applications

    National Research Council Canada - National Science Library

    ...--has grown significantly in the past 20 years. This volume presents a comprehensive report on the state of the field, with an interdisciplinary viewpoint, case studies of fracture sites, illustrations, conclusions, and research recommendations...

  9. Modelling tracer transport in fractured rock at Stripa

    International Nuclear Information System (INIS)

    Herbert, A.

    1992-01-01

    We present the results of a modelling study, making predictions for tracer transport experiments carried out within the H-zone feature in the Stripa mine. We use a direct fracture network approach to represent the system of interconnected flow-conducting fractures comprising this zone. It is a highly fractured granite, and our fracture-network models include up to 60000 fractures. We have had to develop efficient algorithms to calculate the flow and transport through these networks; these techniques are described and justified. The first stage of modelling addressed two saline injection experiments. The results of these were known to us and so in addition to 'predicting' the results of these experiments, we used them to calibrate a flow model of the experimental site. This model was then used to make true 'blind' predictions for a set of tracer experiments carried out in the natural head-field, caused by an open drift. Where our flow model was good, our predictions were found to be very accurate, explaining the dispersion in the tracer breakthrough in terms of the fracture network geometry. Discrepancies for experiments in less well characterised regions of the H-zone are presented, and we suggest that the errors in these predictions are a consequence of the inaccuracies of the flow-field. We have demonstrated the use of large-scale fracture network modelling. It has proved very successful, and made very accurate predictions of field experiments carried out at the Stripa mine. The measured dispersion of tracers can be accounted for by the geometry of the fracture network flow system. (14 refs.) (au)

  10. Porosity, permeability and 3D fracture network characterisation of dolomite reservoir rock samples.

    Science.gov (United States)

    Voorn, Maarten; Exner, Ulrike; Barnhoorn, Auke; Baud, Patrick; Reuschlé, Thierry

    2015-03-01

    With fractured rocks making up an important part of hydrocarbon reservoirs worldwide, detailed analysis of fractures and fracture networks is essential. However, common analyses on drill core and plug samples taken from such reservoirs (including hand specimen analysis, thin section analysis and laboratory porosity and permeability determination) however suffer from various problems, such as having a limited resolution, providing only 2D and no internal structure information, being destructive on the samples and/or not being representative for full fracture networks. In this paper, we therefore explore the use of an additional method - non-destructive 3D X-ray micro-Computed Tomography (μCT) - to obtain more information on such fractured samples. Seven plug-sized samples were selected from narrowly fractured rocks of the Hauptdolomit formation, taken from wellbores in the Vienna basin, Austria. These samples span a range of different fault rocks in a fault zone interpretation, from damage zone to fault core. We process the 3D μCT data in this study by a Hessian-based fracture filtering routine and can successfully extract porosity, fracture aperture, fracture density and fracture orientations - in bulk as well as locally. Additionally, thin sections made from selected plug samples provide 2D information with a much higher detail than the μCT data. Finally, gas- and water permeability measurements under confining pressure provide an important link (at least in order of magnitude) towards more realistic reservoir conditions. This study shows that 3D μCT can be applied efficiently on plug-sized samples of naturally fractured rocks, and that although there are limitations, several important parameters can be extracted. μCT can therefore be a useful addition to studies on such reservoir rocks, and provide valuable input for modelling and simulations. Also permeability experiments under confining pressure provide important additional insights. Combining these and

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

    International Nuclear Information System (INIS)

    Motoyuki Asada; Hitoshi Nakashima; Takashi Ishii; Sumio Horiuchi

    2006-01-01

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

  12. Discrete fracture modelling of the Finnsjoen rock mass. Phase 1: Feasibility study

    International Nuclear Information System (INIS)

    Geier, J.E.; Axelsson, C.L.

    1991-03-01

    The geometry and properties of discrete fractures are expected to control local heterogeneity in flow and solute transport within crystalline rock in the Finnsjoen area. The present report describes the first phase of a discrete-fracture modelling study, the goal of which is to develop stochastic-continuum and hydrologic properties. In the first phase of this study, the FracMan discrete fracture modelling package was used to analyse discrete fracture geometrical and hyrological data. Constant-pressure packer tests were analysed using fractional dimensional methods to estimate effective transmissivities and flow dimension for the packer test intervals. Discrete fracture data on orientation, size, shape, and location were combined with hydrologic data to develop a preliminary conceptual model for the conductive fractures at the site. The variability of fracture properties was expressed in the model by probability distributions. The preliminary conceptual model was used to simulate three-dimensional populations of conductive fractures in 25 m and 50 m cubes of rock. Transient packer tests were simulated in these fracture populations, and the simulated results were used to validate the preliminary conceptual model. The calibrated model was used to estimate the components of effective conductivity tensors for the rock by simulating steady-state groundwater flow through the cubes in three orthogonal directions. Monte Carlo stochastic simulations were performed for alternative realizations of the conceptual model. The number of simulations was insufficient to give a quantitative prediction of the effective conductivity heterogeneity and anisotropy on the scales of the cubes. However, the results give preliminary, rough estimates of these properties, and provide a demonstration of how the discrete-fracture network concept can be applied to derive data that is necessary for stochastic continuum and channel network modelling. (authors)

  13. Structural and neural network analyses of fracture systems at the Aespoe Hard Rock Laboratory, SE Sweden

    International Nuclear Information System (INIS)

    Sirat, M.

    1999-01-01

    The > 10,000 fractures documented in the 450 m deep Aespoe Hard Rock Laboratory (HRL) provide a unique opportunity to study brittle deformation of a Swedish bedrock mass. The fracture population consists of six major sets, one sub-horizontal and five sub-vertical. A classical structural analysis explored the interrelations between geometry and frequency of both dry and wet fractures with respect to depth and in-situ stresses. Three main findings are: In-situ stresses govern frequency distributions of dilated, hence water-bearing fractures. About 68.5% of sub-horizontal fractures are dilated in the thrust regime above a depth of ca. 230 m while 53% of sub-vertical fractures are dilated in the underlying wrench regime. Fractures curve both horizontally and vertically, a finding confirmed by the application of artificial neural networks that included Back-Propagation and Self-Organizing (Kohonen) networks. The asymmetry of the total fracture population and tilts of the sub-Cambrian peneplain demonstrates that multiple reactivations of fractures have tilted the Aespoe rock mass 6 deg to the west. The potential space problem raised by this tilt is negated by systematic curvature of steep fractures, some of which sole out to gently dipping fracture zones. Fractures probably developed their curvature when they formed deep in crystalline crust in Precambrian times but have since reactivated at shallow depths. These findings add significantly to the conceptual model of Aespoe and should be taken into account in future studies regarding the isolation of Sweden's high-grade radioactive waste in crystalline bedrock

  14. Coupled hydro-thermo-mechanical modeling of hydraulic fracturing in quasi-brittle rocks using BPM-DEM

    Directory of Open Access Journals (Sweden)

    Ingrid Tomac

    2017-02-01

    Full Text Available This paper presents an improved understanding of coupled hydro-thermo-mechanical (HTM hydraulic fracturing of quasi-brittle rock using the bonded particle model (BPM within the discrete element method (DEM. BPM has been recently extended by the authors to account for coupled convective–conductive heat flow and transport, and to enable full hydro-thermal fluid–solid coupled modeling. The application of the work is on enhanced geothermal systems (EGSs, and hydraulic fracturing of hot dry rock (HDR is studied in terms of the impact of temperature difference between rock and a flowing fracturing fluid. Micro-mechanical investigation of temperature and fracturing fluid effects on hydraulic fracturing damage in rocks is presented. It was found that fracture is shorter with pronounced secondary microcracking along the main fracture for the case when the convective–conductive thermal heat exchange is considered. First, the convection heat exchange during low-viscosity fluid infiltration in permeable rock around the wellbore causes significant rock cooling, where a finger-like fluid infiltration was observed. Second, fluid infiltration inhibits pressure rise during pumping and delays fracture initiation and propagation. Additionally, thermal damage occurs in the whole area around the wellbore due to rock cooling and cold fluid infiltration. The size of a damaged area around the wellbore increases with decreasing fluid dynamic viscosity. Fluid and rock compressibility ratio was found to have significant effect on the fracture propagation velocity.

  15. Studying physical properties of deformed intact and fractured rocks by micro-scale hydro-mechanical-seismicity model

    Science.gov (United States)

    Raziperchikolaee, Samin

    The pore pressure variation in an underground formation during hydraulic stimulation of low permeability formations or CO2 sequestration into saline aquifers can induce microseismicity due to fracture generation or pre-existing fracture activation. While the analysis of microseismic data mainly focuses on mapping the location of fractures, the seismic waves generated by the microseismic events also contain information for understanding of fracture mechanisms based on microseismic source analysis. We developed a micro-scale geomechanics, fluid-flow and seismic model that can predict transport and seismic source behavior during rock failure. This model features the incorporation of microseismic source analysis in fractured and intact rock transport properties during possible rock damage and failure. The modeling method considers comprehensive grains and cements interaction through a bonded-particle-model. As a result of grain deformation and microcrack development in the rock sample, forces and displacements in the grains involved in the bond breakage are measured to determine seismic moment tensor. In addition, geometric description of the complex pore structure is regenerated to predict fluid flow behavior of fractured samples. Numerical experiments are conducted for different intact and fractured digital rock samples, representing various mechanical behaviors of rocks and fracture surface properties, to consider their roles on seismic and transport properties of rocks during deformation. Studying rock deformation in detail provides an opportunity to understand the relationship between source mechanism of microseismic events and transport properties of damaged rocks to have a better characterizing of fluid flow behavior in subsurface formations.

  16. HYFRAC3D, 3-D Hydraulic Rock Fracture Propagation by Finite Element Method

    International Nuclear Information System (INIS)

    Advani, S.H.; Lee, J.K.; Lee, T.S.

    2001-01-01

    1 - Description of program or function: HYFRAC3D is a finite element program for simulation of three-dimensional fracture geometries with a two-dimensional planar solution. The model predicts the height, width and wing length over time for a hydraulic fracture propagating in a multi-layered system of rock with variable fluid flow and rock mechanics properties. 2 - Method of solution: The program uses the finite element Method of solution. A backward difference scheme is used by taking the weight functions on the time axis. This implicit time matching scheme requires iteration since the fracture configuration at time t+dt is not known. 3 - Restrictions on the complexity of the problem: Graphics output is not available and program is limited to fracture propagation in a single plane without proppant transport

  17. PARTRACK - A particle tracking algorithm for transport and dispersion of solutes in a sparsely fractured rock

    International Nuclear Information System (INIS)

    Svensson, Urban

    2001-04-01

    A particle tracking algorithm, PARTRACK, that simulates transport and dispersion in a sparsely fractured rock is described. The main novel feature of the algorithm is the introduction of multiple particle states. It is demonstrated that the introduction of this feature allows for the simultaneous simulation of Taylor dispersion, sorption and matrix diffusion. A number of test cases are used to verify and demonstrate the features of PARTRACK. It is shown that PARTRACK can simulate the following processes, believed to be important for the problem addressed: the split up of a tracer cloud at a fracture intersection, channeling in a fracture plane, Taylor dispersion and matrix diffusion and sorption. From the results of the test cases, it is concluded that PARTRACK is an adequate framework for simulation of transport and dispersion of a solute in a sparsely fractured rock

  18. Quantifying Groundwater Availability in Fractured Rock Aquifers of Northern Ugandan Refugee Settlements

    Science.gov (United States)

    Frederiks, R.; Lowry, C.; Mutiibwa, R.; Moisy, S.; Thapa, L.; Oriba, J.

    2017-12-01

    In the past two years, Uganda has witnessed an influx of nearly one million refugees who have settled in the sparsely populated northwestern region of the country. This rapid population growth has created high demand for clean water resources. Water supply has been unable to keep pace with demand because the fractured rock aquifers underlying the region often produce low yielding wells. To facilitate management of groundwater resources, it is necessary to quantify the spatial distribution of groundwater. In fractured rock aquifers, there is significant spatial variability in water storage because fractures must be both connected and abundant for water to be extracted in usable quantities. Two conceptual models were evaluated to determine the groundwater storage mechanism in the fractured crystalline bedrock aquifers of northwestern Uganda where by permeability is controlled by faulting, which opens up fractures in the bedrock, or weathering, which occurs when water dissolves components of rock. In order to test these two conceptual models, geologic well logs and available hydrologic data were collected and evaluated using geostatistical and numerical groundwater models. The geostatistical analysis focused on identifying spatially distributed patterns of high and low water yield. The conceptual models were evaluated numerically using four inverse groundwater MODFLOW models based on head and estimated flux targets. The models were based on: (1) the mapped bedrock units using an equivalent porous media approach (2) bedrock units with the addition of known fault zones (3) bedrock units with predicted units of deep weathering based on surface slopes, and (4) bedrock units with discrete faults and simulated weathered zones. Predicting permeable zones is vital for water well drilling in much of East Africa and South America where there is an abundance of both fractured rock and tectonic activity. Given that the population of these developing regions is growing, the demand

  19. A numerical analytic method for electromagnetic radiation accompanying with fracture of rocks

    International Nuclear Information System (INIS)

    Zhen, Chen; Ka-Ma, Huang

    2010-01-01

    This paper studies Rabinovitch's compression experiments on granite and chalk and proposes an oscillating dipole model to analyse and simulate the electromagnetic radiation phenomenon caused by fracture of rocks. Our model assumes that the electromagnetic radiation pulses are initiated by vibrations of the charged rock grains on the tips of the crack. The vibrations of the rock grains are stimulated by the pulses of the cracks. Our simulations show comparable results with Rabinovitch's compression experiments. From the simulation results, it verifies an assumption that the crack width is inversely proportional to the circular frequency electromagnetic radiation, which is presented by Rabinovitch et al. The simulation results also imply that, by using our oscillating dipole model together with Rabinovitch's two equations about the crack length and crack width, we can quantitatively analyse and simulate the electromagnetic radiation phenomenon, which is induced from the fracture of the rocks. (fluids, plasmas and electric discharges)

  20. Scale and size effects in dynamic fracture of concretes and rocks

    Directory of Open Access Journals (Sweden)

    Petrov Y.

    2015-01-01

    Full Text Available Structural-temporal approach based on the notion of incubation time is used for interpretation of strain-rate effects in the fracture process of concretes and rocks. It is established that temporal dependences of concretes and rocks are calculated by the incubation time criterion. Experimentally observed different relations between ultimate stresses of concrete and mortar in static and dynamic conditions are explained. It is obtained that compressive strength of mortar at a low strain rate is greater than that of concrete, but at a high strain rate the opposite is true. Influence of confinement pressure on the mechanism of dynamic strength for concretes and rocks is discussed. Both size effect and scale effect for concrete and rocks samples subjected to impact loading are analyzed. Statistical nature of a size effect contrasts to a scale effect that is related to the definition of a spatio-temporal representative volume determining the fracture event on the given scale level.

  1. Long-range spatial dependence in fractured rock. Empirical evidence and implications for tracer transport

    International Nuclear Information System (INIS)

    Painter, S.

    1999-02-01

    Nonclassical stochastic continuum models incorporating long-range spatial dependence are evaluated as models for fractured crystalline rock. Open fractures and fracture zones are not modeled explicitly in this approach. The fracture zones and intact rock are modeled as a single stochastic continuum. The large contrasts between the fracture zones and unfractured rock are accounted for by making use of random field models specifically designed for highly variable systems. Hydraulic conductivity data derived from packer tests in the vicinity of the Aespoe Hard Rock Laboratory form the basis for the evaluation. The Aespoe log K data were found to be consistent with a fractal scaling model based on bounded fractional Levy motion (bfLm), a model that has been used previously to model highly variable sedimentary formations. However, the data are not sufficient to choose between this model, a fractional Brownian motion model for the normal-score transform of log K, and a conventional geostatistical model. Stochastic simulations conditioned by the Aespoe data coupled with flow and tracer transport calculations demonstrate that the models with long-range dependence predict earlier arrival times for contaminants. This demonstrates the need to evaluate this class of models when assessing the performance of proposed waste repositories. The relationship between intermediate-scale and large-scale transport properties in media with long-range dependence is also addressed. A new Monte Carlo method for stochastic upscaling of intermediate-scale field data is proposed

  2. Rock mechanics issues and research needs in the disposal of wastes in hydraulic fractures

    International Nuclear Information System (INIS)

    Doe, T.W.; McClain, W.C.

    1984-07-01

    The proposed rock mechanics studies outlined in this document are designed to answer the basic questions concerning hydraulic fracturing for waste disposal. These questions are: (1) how can containment be assured for Oak Ridge or other sites; and (2) what is the capacity of a site. The suggested rock mechanics program consists of four major tasks: (1) numerical modeling, (2) laboratory testing, (3) field testing, and (4) monitoring. These tasks are described

  3. Radionuclide Transport in Fractured Rock: Numerical Assessment for High Level Waste Repository

    Directory of Open Access Journals (Sweden)

    Claudia Siqueira da Silveira

    2013-01-01

    Full Text Available Deep and stable geological formations with low permeability have been considered for high level waste definitive repository. A common problem is the modeling of radionuclide migration in a fractured medium. Initially, we considered a system consisting of a rock matrix with a single planar fracture in water saturated porous rock. Transport in the fracture is assumed to obey an advection-diffusion equation, while molecular diffusion is considered the dominant mechanism of transport in porous matrix. The partial differential equations describing the movement of radionuclides were discretized by finite difference methods, namely, fully explicit, fully implicit, and Crank-Nicolson schemes. The convective term was discretized by the following numerical schemes: backward differences, centered differences, and forward differences. The model was validated using an analytical solution found in the literature. Finally, we carried out a simulation with relevant spent fuel nuclide data with a system consisting of a horizontal fracture and a vertical fracture for assessing the performance of a hypothetical repository inserted into the host rock. We have analysed the bentonite expanded performance at the beginning of fracture, the quantified radionuclide released from a borehole, and an estimated effective dose to an adult, obtained from ingestion of well water during one year.

  4. Dynamic Fracturing Behavior of Layered Rock with Different Inclination Angles in SHPB Tests

    Directory of Open Access Journals (Sweden)

    Jiadong Qiu

    2017-01-01

    Full Text Available The fracturing behavior of layered rocks is usually influenced by bedding planes. In this paper, five groups of bedded sandstones with different bedding inclination angles θ are used to carry out impact compression tests by split Hopkinson pressure bar. A high-speed camera is used to capture the fracturing process of specimens. Based on testing results, three failure patterns are identified and classified, including (A splitting along bedding planes; (B sliding failure along bedding planes; (C fracturing across bedding planes. The failure pattern (C can be further classified into three subcategories: (C1 fracturing oblique to loading direction; (C2 fracturing parallel to loading direction; (C3 mixed fracturing across bedding planes. Meanwhile, a numerical model of layered rock and SHPB system are established by particle flow code (PFC. The numerical results show that the shear stress is the main reason for inducing the damage along bedding plane at θ = 0°~75°. Both tensile stress and shear stress on bedding planes contribute to the splitting failure along bedding planes when the inclination angle is 90°. Besides, tensile stress is the main reason that leads to the damage in rock matrixes at θ = 0°~90°.

  5. Modeling of Hydrodynamic Chromatography for Colloid Migration in Fractured Rock

    International Nuclear Information System (INIS)

    Li Shihhai; Jen, C.-P.

    2001-01-01

    The role of colloids in the migration of radionuclides in the geosphere has been emphasized in the performance assessment of high-level radioactive waste disposal. The literature indicates that the colloid velocity may not be equal to the velocity of groundwater owing to hydrodynamic chromatography. A theoretical model for hydrodynamic chromatography of colloid migration in the fracture is proposed in the present work. In this model, the colloids are treated as nonreactive and the external forces acting on colloidal particles are considered including the inertial force, the van der Waals attractive force, and the electrical double-layer repulsive force, as well as the gravitational force. A fully developed concentration profile for colloids is obtained to elucidate migration behavior for colloids in the fracture. The effects of parameters governing these forces and the aperture of the fracture are determined using a theoretical model

  6. A NEW HIGH RESOLUTION OPTICAL METHOD FOR OBTAINING THE TOPOGRAPHY OF FRACTURE SURFACES IN ROCKS

    Directory of Open Access Journals (Sweden)

    Steven Ogilvie

    2011-05-01

    Full Text Available Surface roughness plays a major role in the movement of fluids through fracture systems. Fracture surface profiling is necessary to tune the properties of numerical fractures required in fluid flow modelling to those of real rock fractures. This is achieved using a variety of (i mechanical and (ii optical techniques. Stylus profilometry is a popularly used mechanical method and can measure surface heights with high precision, but only gives a good horizontal resolution in one direction on the fracture plane. This method is also expensive and simultaneous coverage of the surface is not possible. Here, we describe the development of an optical method which images cast copies of rough rock fractures using in-house developed hardware and image analysis software (OptiProf™ that incorporates image improvement and noise suppression features. This technique images at high resolutions, 15-200 μm for imaged areas of 10 × 7.5 mm and 100 × 133 mm, respectively and a similar vertical resolution (15 μm for a maximum topography of 4 mm. It uses in-house developed hardware and image analysis (OptiProf™ software and is cheap and non-destructive, providing continuous coverage of the fracture surface. The fracture models are covered with dye and fluid thicknesses above the rough surfaces converted into topographies using the Lambert-Beer Law. The dye is calibrated using 2 devices with accurately known thickness; (i a polycarbonate tile with wells of different depths and (ii a wedge-shaped vial made from silica glass. The data from each of the two surfaces can be combined to provide an aperture map of the fracture for the scenario where the surfaces touch at a single point or any greater mean aperture. The topography and aperture maps are used to provide data for the generation of synthetic fractures, tuned to the original fracture and used in numerical flow modelling.

  7. A study on the characteristics of site-scale fracture system in granite and volcanic rock

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Kyung Su; Kim, Chun Soo; Bae, Dae Seok; Park, Byoung Yoon; Koh, Young Kown [Korea Atomic Energy Research Institute, Taejeon (Korea)

    2000-03-01

    The safety of waste disposal can be achieved by a complete isolation of radioactive wastes from biosphere or by a retardation of nuclide migration to reach an acceptable dose level. For the deep geological disposal of high-level radioactive waste, the potential pathways of nuclide primarily depend on the spatial distribution characteristics of conductive fractures. Major key issues in the quantification of fracture system for a disposal site are involved in classification criteria, hydraulic parameters, geometry, field investigation methods etc. This research aims to characterize the spatial distribution characteristics of conductive fractures in granite and volcanic rock mass. 10 refs., 32 figs., 13 tabs. (Author)

  8. Simulation of water seepage through a vadose zone in fractured rock

    International Nuclear Information System (INIS)

    Fuentes, Nestor O.

    2003-01-01

    In order to improve our understanding of the vadose zone in fractured rock, obtaining useful tools to simulate, predict and prevent subsurface contamination, a three-dimensional model has been developed from the base of recent two-dimensional codes. Fracture systems are simulated by means of a dynamical evolution of a random-fuse network model, and the multiphase expression of Richards equation is used to describe fluid displacements. Physical situations presented here emphasized the importance of fracture connectivity and spatial variability on the seepage evolution through the vadose zone, and confirm the existence of dendritic patterns along localized preferential paths. (author)

  9. A constitutive model for representing coupled creep, fracture, and healing in rock salt

    International Nuclear Information System (INIS)

    Chan, K.S.; Bodner, S.R.; Munson, D.E.; Fossum, A.F.

    1996-01-01

    The development of a constitutive model for representing inelastic flow due to coupled creep, damage, and healing in rock salt is present in this paper. This model, referred to as Multimechanism Deformation Coupled Fracture model, has been formulated by considering individual mechanisms that include dislocation creep, shear damage, tensile damage, and damage healing. Applications of the model to representing the inelastic flow and fracture behavior of WIPP salt subjected to creep, quasi-static loading, and damage healing conditions are illustrated with comparisons of model calculations against experimental creep curves, stress-strain curves, strain recovery curves, time-to-rupture data, and fracture mechanism maps

  10. Role of large-scale permeability measurements in fractured rock and their application at Stripa

    International Nuclear Information System (INIS)

    Witherspoon, P.A.; Wilson, C.R.; Long, J.C.S.; DuBois, A.O.; Gale, J.E.; McPherson, M.

    1979-10-01

    Completion of the macropermeability experiment will provide: (i) a direct, in situ measurement of the permeability of 10 5 to 10 6 m 3 of rock; (ii) a potential method for confirming the analysis of a series of small scale permeability tests performed in surface and underground boreholes; (iii) a better understanding of the effect to open borehole zone length on pressure measurement; (iv) increased volume in fractured rock; (v) a basis for evaluating the ventilation technique for flow measurement in large scale testing of low permeability rocks

  11. Evolution of fracture permeability of ultramafic rocks undergoing serpentinization at hydrothermal conditions: An experimental study

    Science.gov (United States)

    Farough, Aida; Moore, Diane E.; Lockner, David A.; Lowell, R.P.

    2016-01-01

    We performed flow-through laboratory experiments on five cylindrically cored samples of ultramafic rocks, in which we generated a well-mated through-going tensile fracture, to investigate evolution of fracture permeability during serpentinization. The samples were tested in a triaxial loading machine at a confining pressure of 50 MPa, pore pressure of 20 MPa, and temperature of 260°C, simulating a depth of 2 km under hydrostatic conditions. A pore pressure difference of up to 2 MPa was imposed across the ends of the sample. Fracture permeability decreased by 1–2 orders of magnitude during the 200–330 h experiments. Electron microprobe and SEM data indicated the formation of needle-shaped crystals of serpentine composition along the walls of the fracture, and chemical analyses of sampled pore fluids were consistent with dissolution of ferro-magnesian minerals. By comparing the difference between fracture permeability and matrix permeability measured on intact samples of the same rock types, we concluded that the contribution of the low matrix permeability to flow is negligible and essentially all of the flow is focused in the tensile fracture. The experimental results suggest that the fracture network in long-lived hydrothermal circulation systems can be sealed rapidly as a result of mineral precipitation, and generation of new permeability resulting from a combination of tectonic and crystallization-induced stresses is required to maintain fluid circulation.

  12. External fixation to correct tarsal-metatarsal fracture in rock pigeon (Columba livia

    Directory of Open Access Journals (Sweden)

    Leandro Almeida Rui

    Full Text Available ABSTRACT Orthopedic conditions, such as bone fractures, are very common in avian medicine. External fixators have been considered the gold standard for birds, since they allow early movement of the limbs and minimal invasive surgery. Fractures in several bones have been successfully treated in pigeons. However, to the best of our knowledge, this case represents the first report of successful surgical repair of tarsal-metatarsal fracture in rock pigeon. External fixator was made with four 24G catheters, being inserted manually proximal and distal to the fracture and connected with polymerizable acrylic. Radiographic consolidation of fracture was observed 60 days post-surgery and anti-inflammatory and antibiotic protocols were successful on avoiding pain and infection during surgery and bone healing.

  13. A Study on the Fracture Control of Rock Bolts in High Ground Pressure Roadways of Deep Mines

    Directory of Open Access Journals (Sweden)

    Wen Jinglin

    2015-01-01

    Full Text Available According to the frequent fractures of rock bolts in high ground pressure roadways of deep mines, this paper analyzes the mechanism of fractures and concludes that high ground pressure and material de-fects are main reasons for the fracture of rock bolts. The basic idea of fracture control of rock bolts in high ground pressure roadways of deep mines is to increase the yield load and the limit load of rock bolt materials and reduce the actual load of rock bolts. There are four ways of controlling rock bolt fracture: increasing the rock bolt diameter, strengthening bolt materials, weakening support rigidity and the implementation of double supporting. With the roadway support of the 2302 working face of a coal mine as the project background, this paper carries out a study on the effect of two schemes, increasing the rock bolt diameter and the double supporting technique through methods of theoretical analysis, numerical simulation and so on. It determines the most reasonable diam-eter of rock bolts and the best delay distance of secondary support. Practices indicate that rock bolt fracture can be effectively controlled through the double supporting technique, which strengthens the roof and two sides through the first supporting technique and strengthens side angles through the secondary supporting technique.

  14. Free-Surface flow dynamics and its effect on travel time distribution in unsaturated fractured zones - findings from analogue percolation experiments

    Science.gov (United States)

    Noffz, Torsten; Kordilla, Jannes; Dentz, Marco; Sauter, Martin

    2017-04-01

    Flow in unsaturated fracture networks constitutes a high potential for rapid mass transport and can therefore possibly contributes to the vulnerability of aquifer systems. Numerical models are generally used to predict flow and transport and have to reproduce various complex effects of gravity-driven flow dynamics. However, many classical volume-effective modelling approaches often do not grasp the non-linear free surface flow dynamics and partitioning behaviour at fracture intersections in unsaturated fracture networks. Better process understanding can be obtained by laboratory experiments, that isolate single aspects of the mass partitioning process, which influence travel time distributions and allow possible cross-scale applications. We present a series of percolation experiments investigating partitioning dynamics of unsaturated multiphase flow at an individual horizontal fracture intersection. A high precision multichannel dispenser is used to establish gravity-driven free surface flow on a smooth and vertical PMMA (poly(methyl methacrylate)) surface at rates ranging from 1.5 to 4.5 mL/min to obtain various flow modes (droplets; rivulets). Cubes with dimensions 20 x 20 x 20 cm are used to create a set of simple geometries. A digital balance provides continuous real-time cumulative mass bypassing the network. The influence of variable flow rate, atmospheric pressure and temperature on the stability of flow modes is shown in single-inlet experiments. Droplet and rivulet flow are delineated and a transition zone exhibiting mixed flow modes can be determined. Furthermore, multi-inlet setups with constant total inflow rates are used to reduce variance and the effect of erratic free-surface flow dynamics. Investigated parameters include: variable aperture widths df, horizontal offsets dv of the vertical fracture surface and alternating injection methods for both droplet and rivulet flow. Repetitive structures with several horizontal fractures extend arrival times

  15. 3D Simulation of Multiple Simultaneous Hydraulic Fractures with Different Initial Lengths in Rock

    Science.gov (United States)

    Tang, X.; Rayudu, N. M.; Singh, G.

    2017-12-01

    Hydraulic fracturing is widely used technique for extracting shale gas. During this process, fractures with various initial lengths are induced in rock mass with hydraulic pressure. Understanding the mechanism of propagation and interaction between these induced hydraulic cracks is critical for optimizing the fracking process. In this work, numerical results are presented for investigating the effect of in-situ parameters and fluid properties on growth and interaction of multi simultaneous hydraulic fractures. A fully coupled 3D fracture simulator, TOUGH- GFEM is used for simulating the effect of different vital parameters, including in-situ stress, initial fracture length, fracture spacing, fluid viscosity and flow rate on induced hydraulic fractures growth. This TOUGH-GFEM simulator is based on 3D finite volume method (FVM) and partition of unity element method (PUM). Displacement correlation method (DCM) is used for calculating multi - mode (Mode I, II, III) stress intensity factors. Maximum principal stress criteria is used for crack propagation. Key words: hydraulic fracturing, TOUGH, partition of unity element method , displacement correlation method, 3D fracturing simulator

  16. Hydromechanical coupling in fractured rock masses: mechanisms and processes of selected case studies

    Science.gov (United States)

    Zangerl, Christian

    2015-04-01

    Hydromechanical (HM) coupling in fractured rock play an important role when events including dam failures, landslides, surface subsidences due to water withdrawal or drainage, injection-induced earthquakes and others are analysed. Generally, hydromechanical coupling occurs when a rock mass contain interconnected pores and fractures which are filled with water and pore/fracture pressures evolves. In the on hand changes in the fluid pressure can lead to stress changes, deformations and failures of the rock mass. In the other hand rock mass stress changes and deformations can alter the hydraulic properties and fluid pressures of the rock mass. Herein well documented case studies focussing on surface subsidence due to water withdrawal, reversible deformations of large-scale valley flanks and failure as well as deformation processes of deep-seated rock slides in fractured rock masses are presented. Due to pore pressure variations HM coupling can lead to predominantly reversible rock mass deformations. Such processes can be considered by the theory of poroelasticity. Surface subsidence reaching magnitudes of few centimetres and are caused by water drainage into deep tunnels are phenomenas which can be assigned to processes of poroelasticity. Recently, particular focus was given on large tunnelling projects to monitor and predict surface subsidence in fractured rock mass in oder to avoid damage of surface structures such as dams of large reservoirs. It was found that surface subsidence due to tunnel drainage can adversely effect infrastructure when pore pressure drawdown is sufficiently large and spatially extended and differential displacements which can be amplified due to topographical effects e.g. valley closure are occurring. Reversible surface deformations were also ascertained on large mountain slopes and summits with the help of precise deformation measurements i.e. permanent GPS or episodic levelling/tacheometric methods. These reversible deformations are often

  17. Finite element simulations of interactions between multiple hydraulic fractures in a poroelastic rock

    DEFF Research Database (Denmark)

    Salimzadeh, Saeed; Usui, Tomoya; Paluszny, Adriana

    2017-01-01

    A fully coupled three-dimensional finite-element model for hydraulic fractures in permeable rocks is presented, and used to investigate the ranges of applicability of the classical analytical solutions that are known to be valid in limiting cases. This model simultaneously accounts for fluid flow...

  18. Three-Dimensional poroelastic effects during hydraulic fracturing in permeable rocks

    DEFF Research Database (Denmark)

    Salimzadeh, Saeed; Paluszny, Adriana; Zimmerman, Robert W.

    2017-01-01

    A fully coupled three-dimensional finite-element model for hydraulic fractures in permeable rocks is presented, and used to investigate the ranges of applicability of the classical analytical solutions that are known to be valid in limiting cases. This model simultaneously accounts for fluid flow...

  19. Determination of static moduli in fractured rocks by T-matrix model

    Czech Academy of Sciences Publication Activity Database

    Chalupa, F.; Vilhelm, J.; Petružálek, Matěj; Bukovská, Z.

    2017-01-01

    Roč. 22, č. 1 (2017), s. 22-31 ISSN 1335-1788 Institutional support: RVO:67985831 Keywords : fractured rocks * dynamic and static moduli * T-matrix model * elastic wave velocity * well logging Subject RIV: DB - Geology ; Mineralogy OBOR OECD: Geology Impact factor: 0.769, year: 2016 http://actamont.tuke.sk/pdf/2017/n1/3chalupa.pdf

  20. Flexible parallel implicit modelling of coupled thermal-hydraulic-mechanical processes in fractured rocks

    Science.gov (United States)

    Cacace, Mauro; Jacquey, Antoine B.

    2017-09-01

    Theory and numerical implementation describing groundwater flow and the transport of heat and solute mass in fully saturated fractured rocks with elasto-plastic mechanical feedbacks are developed. In our formulation, fractures are considered as being of lower dimension than the hosting deformable porous rock and we consider their hydraulic and mechanical apertures as scaling parameters to ensure continuous exchange of fluid mass and energy within the fracture-solid matrix system. The coupled system of equations is implemented in a new simulator code that makes use of a Galerkin finite-element technique. The code builds on a flexible, object-oriented numerical framework (MOOSE, Multiphysics Object Oriented Simulation Environment) which provides an extensive scalable parallel and implicit coupling to solve for the multiphysics problem. The governing equations of groundwater flow, heat and mass transport, and rock deformation are solved in a weak sense (either by classical Newton-Raphson or by free Jacobian inexact Newton-Krylow schemes) on an underlying unstructured mesh. Nonlinear feedbacks among the active processes are enforced by considering evolving fluid and rock properties depending on the thermo-hydro-mechanical state of the system and the local structure, i.e. degree of connectivity, of the fracture system. A suite of applications is presented to illustrate the flexibility and capability of the new simulator to address problems of increasing complexity and occurring at different spatial (from centimetres to tens of kilometres) and temporal scales (from minutes to hundreds of years).

  1. Thermo-hydro-mechanical simulation of a 3D fractured porous rock: preliminary study of coupled matrix-fracture hydraulics

    International Nuclear Information System (INIS)

    Canamon, I.; Javier Elorza, F.; Ababou, R.

    2007-01-01

    We present a problem involving the modeling of coupled flow and elastic strain in a 3D fractured porous rock, which requires prior homogenization (up-scaling) of the fractured medium into an equivalent Darcian anisotropic continuum. The governing equations form a system of PDE's (Partial Differential Equations) and, depending on the case being considered, this system may involve two different types of 'couplings' (in a real system, both couplings (1) and (2) generally take place): 1) Hydraulic coupling in a single (no exchange) or in a dual matrix-fracture continuum (exchange); 2) Thermo-Hydro-Mechanical interactions between fluid flow, pressure, elastic stress, strain, and temperature. We present here a preliminary model and simulation results with FEMLAB R , for the hydraulic problem with anisotropic heterogeneous coefficients. The model is based on data collected at an instrumented granitic site (FEBEX project) for studying a hypothetical nuclear waste repository at the Grimsel Test Site in the Swiss Alps. (authors)

  2. Rock mechanics in the disposal of radioactive wastes by hydraulic fracturing

    Energy Technology Data Exchange (ETDEWEB)

    McClain, W C

    1968-01-01

    The ultimate capacity of a hydraulic-fracturing waste disposal facility is governed primarily by the integrity of the rocks overlying the injected wastes. The objective of this study is to analyze theoretically the stresses and strains generated by the injected wastes in an effort to understand the behavior of the system sufficiently well that the failure mechanism can be predicted and the capacity of the injection well estimated. The surface uplifts at Oak Ridge National Laboratory's fracturing site were compared with theoretical curves obtained by assuming the uplifts to be inversely analogous to the subsidence which occurs over mining excavations. This analysis, based on assumptions of homogeneity, isotropy, and linear elasticity, provided considerable insight into the mechanics of the process. The most probable mechanism of failure of the rock appears to be by the formation of a vertical instead of a horizontal fracture. Fracture orientation is controlled primarily by the orientation of the principal stress field in the rock. Each successive waste injection slightly modifies this stress field toward a condition more favorable to the formation of a vertical fracture. (16 refs.)

  3. Modelling of excavation depth and fractures in rock caused by tool indentation

    Energy Technology Data Exchange (ETDEWEB)

    Kou Shaoquan; Tan Xiangchun; Lindqvist, P.A. [Luleaa Univ. of Technology (Sweden)

    1997-10-01

    The hydraulic regime after excavation in the near-field rock around deposition holes and deposition tunnels in a spent nuclear fuel repository is of concern for prediction of the saturation process of bentonite buffer and tunnel backfill. The hydraulic condition of main interest in this context is a result of the fracture network that is caused by the excavation. Modelling of the excavation disturbed zone in hard rocks caused by mechanical excavation has been carried out in the Division of Mining Engineering since 1993. This report contains an overview of the work conducted. The mechanical excavation is reasonably simplified as an indentation process of the interaction between rigid indenters and rocks. A large number of experiments have been carried out in the laboratory, and the results used for identifying crushed zones and fracture systems in rock under indentation are presented based on these experiments. The indentation causes crushing and damage of the rock and results in a crushed zone and a cracked zone. The indenter penetrates the rock with a certain depth when the force is over a threshold value relevant to the rock and tool. Outside the cracked zone there are basically three systems of cracks: median cracks, radial cracks, and side cracks. Fully developed radial cracks on each side of the indented area can connect with each other and join with median crack. This forms the so-called radial/median crack system. The influence of the mechanical properties of the rock is discussed based on our conceptual model, and the main factors governing the indentation event are summarised. The cracked zone is dealt with by an analytical fracture model. The side crack is simulated by applying the boundary element method coupled with fracture mechanics. Functional relationships are established relating either the indentation depth or the length of radial/median cracks to the various quantities characterising the physical event, namely the shape and the size of the

  4. Modelling of excavation depth and fractures in rock caused by tool indentation

    International Nuclear Information System (INIS)

    Kou Shaoquan; Tan Xiangchun; Lindqvist, P.A.

    1997-10-01

    The hydraulic regime after excavation in the near-field rock around deposition holes and deposition tunnels in a spent nuclear fuel repository is of concern for prediction of the saturation process of bentonite buffer and tunnel backfill. The hydraulic condition of main interest in this context is a result of the fracture network that is caused by the excavation. Modelling of the excavation disturbed zone in hard rocks caused by mechanical excavation has been carried out in the Division of Mining Engineering since 1993. This report contains an overview of the work conducted. The mechanical excavation is reasonably simplified as an indentation process of the interaction between rigid indenters and rocks. A large number of experiments have been carried out in the laboratory, and the results used for identifying crushed zones and fracture systems in rock under indentation are presented based on these experiments. The indentation causes crushing and damage of the rock and results in a crushed zone and a cracked zone. The indenter penetrates the rock with a certain depth when the force is over a threshold value relevant to the rock and tool. Outside the cracked zone there are basically three systems of cracks: median cracks, radial cracks, and side cracks. Fully developed radial cracks on each side of the indented area can connect with each other and join with median crack. This forms the so-called radial/median crack system. The influence of the mechanical properties of the rock is discussed based on our conceptual model, and the main factors governing the indentation event are summarised. The cracked zone is dealt with by an analytical fracture model. The side crack is simulated by applying the boundary element method coupled with fracture mechanics. Functional relationships are established relating either the indentation depth or the length of radial/median cracks to the various quantities characterising the physical event, namely the shape and the size of the

  5. Characterizing fractures and shear zones in crystalline rock using seismic and GPR methods

    Science.gov (United States)

    Doetsch, Joseph; Jordi, Claudio; Laaksonlaita, Niko; Gischig, Valentin; Schmelzbach, Cedric; Maurer, Hansruedi

    2016-04-01

    Understanding the natural or artificially created hydraulic conductivity of a rock mass is critical for the successful exploitation of enhanced geothermal systems (EGS). The hydraulic response of fractured crystalline rock is largely governed by the spatial organization of permeable fractures. Defining the 3D geometry of these fractures and their connectivity is extremely challenging, because fractures can only be observed directly at their intersections with tunnels or boreholes. Borehole-based and tunnel-based ground-penetrating radar (GPR) and seismic measurements have the potential to image fractures and other heterogeneities between and around boreholes and tunnels, and to monitor subtle time-lapse changes in great detail. We present the analysis of data acquired in the Grimsel rock laboratory as part of the In-situ Stimulation and Circulation (ISC) experiment, in which a series of stimulation experiments have been and will be performed. The experiments in the granitic rock range from hydraulic fracturing to controlled fault-slip experiments. The aim is to obtain a better understanding of coupled seismo-hydro-mechanical processes associated with high-pressure fluid injections in crystalline rocks and their impact on permeability creation and enhancement. GPR and seismic data have been recorded to improve the geological model and characterize permeable fractures and shear zones. The acquired and processed data include reflection GPR profiles measured from tunnel walls, single-borehole GPR images, and borehole-to-borehole and tunnel-to-tunnel seismic and GPR tomograms. The reflection GPR data reveal the geometry of shear zones up to a distance of 30 m from the tunnels and boreholes, but the interpretation is complicated by the geometrical ambiguity around tunnels and boreholes and by spurious reflections from man-made structures such as boreholes. The GPR and seismic traveltime tomography results reveal brittle fractured rock between two ductile shear zones. The

  6. Radionuclide transport in fractured rock: quantifying releases from final disposal of high level waste

    International Nuclear Information System (INIS)

    Silveira, Claudia S. da; Alvim, Antonio C.M.

    2013-01-01

    Crystalline rock has been considered as a potentially suitable matrix for high-level radioactive waste (HLW) repository because it is found in very stable geological formations and may have very low permeability. In this study the adopted physical system consists of the rock matrix containing a discrete horizontal fracture in a water saturated porous rock and a system of vertical fractures as a lineament. The transport in the fractures - horizontal and vertical, is assumed to obey a relation convection-diffusion, while the molecular diffusion is considered dominant mechanism of transport in porous rock. In this model the decay chain is considered. We use a code in Fortran 90, where the partial differential equations that describe the movement of radionuclides were discretized by finite differences methods. We use the fully implicit method for temporal discretization schemes. The simulation was performed with relevant data of nuclides in spent fuel for performance assessment in a hypothetical repository, thus quantifying the radionuclides released into the host rock. (author)

  7. FIELD-SCALE EFFECTIVE MATRIX DIFFUSION COEFFICIENT FOR FRACTURED ROCK: RESULTS FROM LITERATURE SURVEY

    International Nuclear Information System (INIS)

    Zhou, Q.; Hui-Hai Liu; Molz, F.J.; Zhang, Y.; Bodvarsson, G.S.

    2005-01-01

    Matrix diffusion is an important mechanism for solute transport in fractured rock. We recently conducted a literature survey on the effective matrix diffusion coefficient, D m e , a key parameter for describing matrix diffusion processes at the field scale. Forty field tracer tests at 15 fractured geologic sites were surveyed and selected for the study, based on data availability and quality. Field-scale D m e values were calculated, either directly using data reported in the literature or by reanalyzing the corresponding field tracer tests. Surveyed data indicate that the effective-matrix-diffusion-coefficient factor F D (defined as the ratio of D m e to the lab-scale matrix diffusion coefficient [D m ] of the same tracer) is generally larger than one, indicating that the effective matrix diffusion coefficient in the field is comparatively larger than the matrix diffusion coefficient at the rock-core scale. This larger value can be attributed to the many mass-transfer processes at different scales in naturally heterogeneous, fractured rock systems. Furthermore, we observed a moderate trend toward systematic increase in the F D value with observation scale, indicating that the effective matrix diffusion coefficient is likely to be statistically scale dependent. The F D value ranges from 1 to 10,000 for observation scales from 5 to 2,000 m. At a given scale, the F D value varies by two orders of magnitude, reflecting the influence of differing degrees of fractured rock heterogeneity at different sites. In addition, the surveyed data indicate that field-scale longitudinal dispersivity generally increases with observation scale, which is consistent with previous studies. The scale-dependent field-scale matrix diffusion coefficient (and dispersivity) may have significant implications for assessing long-term, large-scale radionuclide and contaminant transport events in fractured rock, both for nuclear waste disposal and contaminant remediation

  8. Modelling for the Stripa site characterization and validation drift inflow: prediction of flow through fractured rock

    International Nuclear Information System (INIS)

    Herbert, A.; Gale, J.; MacLeod, R.; Lanyon, G.

    1991-12-01

    We present our approach to predicting flow through a fractured rock site; the site characterization and validation region in the Stripa mine. Our approach is based on discrete fracture network modelling using the NAPSAC computer code. We describe the conceptual models and assumptions that we have used to interpret the geometry and flow properties of the fracture networks, from measurements at the site. These are used to investigate large scale properties of the network and we show that for flows on scales larger than about 10 m, porous medium approximation should be used. The porous medium groundwater flow code CFEST is used to predict the large scale flows through the mine and the SCV region. This, in turn, is used to provide boundary conditions for more detailed models, which predict the details of flow, using a discrete fracture network model, on scales of less than 10 m. We conclude that a fracture network approach is feasible and that it provides a better understanding of details of flow than conventional porous medium approaches and a quantification of the uncertainty associated with predictive flow modelling characterised from field measurement in fractured rock. (au)

  9. Natural spatial and temporal variations in groundwater chemistry in fractured, sedimentary rocks: scale and implications for solute transport

    International Nuclear Information System (INIS)

    Hoven, Stephen J. van der; Kip Solomon, D.; Moline, Gerilynn R.

    2005-01-01

    Natural tracers (major ions, δ 18 O, and O 2 ) were monitored to evaluate groundwater flow and transport to a depth of 20 m below the surface in fractured sedimentary (primarily shale and limestone) rocks. Large temporal variations in these tracers were noted in the soil zone and the saprolite, and are driven primarily by individual storm events. During nonstorm periods, an upward flow brings water with high TDS, constant δ 18 O, and low dissolved O 2 to the water table. During storm events, low TDS, variable δ 18 O, and high dissolved O 2 water recharges through the unsaturated zone. These oscillating signals are rapidly transmitted along fracture pathways in the saprolite, with changes occurring on spatial scales of several meters and on a time scale of hours. The variations decreased markedly below the boundary between the saprolite and less weathered bedrock. Variations in the bedrock units occurred on time scales of days and spatial scales of at least 20 m. The oscillations of chemical conditions in the shallow groundwater are hypothesized to have significant implications for solute transport. Solutes and colloids that adsorb onto aquifer solids can be released into solution by decreases in ionic strength and pH. The decreases in ionic strength also cause thermodynamic undersaturation of the groundwater with respect to some mineral species and may result in mineral dissolution. Redox conditions are also changing and may result in mineral dissolution/precipitation. The net result of these chemical variations is episodic transport of a wide range of dissolved solutes or suspended particles, a phenomenon rarely considered in contaminant transport studies

  10. Relative Abundances of Calcite and Silica in Fracture Coatings as a Possible Indicator of Evaporation in a Thick Unsaturated Zone, Yucca Mountain, Nevada

    Science.gov (United States)

    Marshall, B. D.; Moscati, R. J.

    2005-12-01

    Yucca Mountain, a ridge of shallowly dipping, Miocene-age volcanic rocks in southwest Nevada, is the proposed site for a nuclear waste repository to be constructed in the 500- to 700-m-thick unsaturated zone (UZ). At the proposed repository, the 300-m-thick Topopah Spring Tuff welded unit (TSw) is overlain by approximately 30 m of nonwelded tuffs (PTn); the Tiva Canyon Tuff welded unit (TCw) overlies the PTn with a range in thickness from 0 to approximately 130 m at the site. The amount of water percolation through the UZ is low and difficult to measure directly, but local seepage into mined tunnels has been observed in the TCw. Past water seepage in the welded tuffs is recorded by widespread, thin (0.3 cm) coatings of calcite and silica on fracture surfaces and within cavities. Abundances of calcite and silica in the coatings were determined by X-ray microfluorescence mapping and subsequent multispectral image analysis of over 200 samples. The images were classified into constituent phases including opal-chalcedony-quartz (secondary silica) and calcite. In the TCw samples, the median calcite/silica ratio is 8; in the TSw samples within 35 m below the PTn, median calcite/silica falls to 2, perhaps reflecting an increase in soluble silica from the presence of glass in the nonwelded tuffs. In the deeper parts of the TSw, median calcite/silica reaches 100 and many samples contain no detectable secondary silica phase. Evaporation and changing pCO2 control precipitation of calcite from water percolating downward in the UZ, but precipitation of opal requires only evaporation. Calcite/silica ratios, therefore, can constrain the relative importance of evaporation in the UZ. Although calcite/silica values scatter widely within the TSw, reflecting the spatial variability of gas and water flow, average calcite/silica ratios increase with stratigraphic depth, indicating less evaporation at the deeper levels of the UZ. Coupled with the much smaller calcite/silica ratios

  11. Views on the calculation of flow and dispersion processes in fractured rock

    International Nuclear Information System (INIS)

    Joensson, Lennart

    1990-03-01

    In the report some basic aspects on model types, physical processes, determination of parameters are discussed in relation to a description of flow and dispersion processes in fractured rocks. As far as model types concern it is shown that Darcy's law and the dispersion equation are not especially applicable. These equations can only describe an average situation of flow and spreading while in reality very large deviations could exist between an average situation and the flow and concentration distribution for a certain fracture geometry. The reason for this is primarily the relation between the length scales for the repository and the near field and the fracture system respectively and the poor connectivity between fractures or expressed in another way - the geosphere can not be treated as a continuous medium. The statistical properties of the fractures and the fracture geometry cause large uncertainties in at least two respects: * boundary conditions as to groundwater flow at the repository and thus the mass flow of radioactive material * distribution of flows and concentrations in planes in the geosphere on different distances from the repository. A realistic evaluation of transport and spreading of radioactive material by the groundwater in the geosphere thus requires that the possible variation or uncertainty of the water conducting characteristics of the fracture system is considered. A possible approach is then to describe flow in the geosphere on the basic of the flow in single fractures which are hydraulically connected to each other so that a flow in a fracture system is obtained. The discussion on physical processes which might influence the flow description in single fractures is concentrated to three aspects - factors driving the flow besides the ordinary hydraulic gradient, the viscous properties of water in a very small space (such as a fracture), the influence on the flow of heat release from the repository. (42 figs., 28 refs.)

  12. Reflection seismic methods applied to locating fracture zones in crystalline rock

    International Nuclear Information System (INIS)

    Juhlin, C.

    1998-01-01

    The reflection seismic method is a potentially powerful tool for identifying and localising fracture zones in crystalline rock if used properly. Borehole sonic logs across fracture zones show that they have reduced P-wave velocities compared to the surrounding intact rock. Diagnostically important S-wave velocity log information across the fracture zones is generally lacking. Generation of synthetic reflection seismic data and subsequent processing of these data show that structures dipping up towards 70 degrees from horizontal can be reliably imaged using surface seismic methods. Two real case studies where seismic reflection methods have been used to image fracture zones in crystalline rock are presented. Two examples using reflection seismic are presented. The first is from the 5354 m deep SG-4 borehole in the Middle Urals, Russia where strong seismic reflectors dipping from 25 to 50 degrees are observed on surface seismic reflection data crossing over the borehole. On vertical seismic profile data acquired in the borehole, the observed P-wave reflectivity is weak from these zones, however, strong converted P to S waves are observed. This can be explained by the source of the reflectors being fracture zones with a high P wave to S wave velocity ratio compared to the surrounding rock resulting in a high dependence on the angle of incidence for the reflection coefficient. A high P wave to S wave velocity ratio (high Poisson's ratio) is to be expected in fluid filled fractured rock. The second case is from Aevroe, SE Sweden, where two 1 km long crossing high resolution seismic reflection lines were acquired in October 1996. An E-W line was shot with 5 m geophone and shotpoint spacing and a N-S one with 10 m geophone and shotpoint spacing. An explosive source with a charge size of 100 grams was used along both lines. The data clearly image three major dipping reflectors in the upper 200 ms (600 m). The dipping ones intersect or project to the surface at/or close to

  13. Study of strontium and cesium migration in fractured crystalline rock

    International Nuclear Information System (INIS)

    Gustafsson, E.; Klockars, C.E.

    1984-01-01

    The purpose of this investigation has been to study the retardation and dilution of non-active strontium and cesium relative to a non-absorbing substance (iodide) in a well-defined fracture zone in the Finnsjoen field research area. The investigation was carried out in a previously tracer-tested fracture zone. The study has encompassed two separate test runs with prolonged injection of strontium and iodide and of cesium and iodide. The test have shown that: - Strontium is not retarded, but rather absorbed to about 40% at equilibrium. - At injection stop, 36.3% of the injected mass of strontium has been absorbed and there is no deabsorption. -Cesium is retarded a factor of 2-3 and absorbed to about 30% at equilibrium. - At injection stop, 39.4% of the injected mass of cesium has been absorbed. Cesium is deabsorbed after injection stop (400h) and after 1300 hours, only 22% of the injected mass of cesium is absorbed. (author)

  14. Fracture detection in crystalline rock using ultrasonic shear waves

    International Nuclear Information System (INIS)

    Waters, K.H.; Palmer, S.P.; Farrell, W.E.

    1978-12-01

    An ultrasonic shear wave reflection profiling system for use in the detection of water-filled cracks occurring within a crystalline rock mass is being tested in a laboratory environment. Experiments were performed on an irregular tensile crack induced approximately 0.5 m below one circular face of a 1.0-m-dia, 1.8-m-long granite cylinder. Good reflection data were obtained from this irregular crack with the crack either air filled or water filled. Data were collected that suggest a frequency-dependent S/sub H/ wave reflection coefficient for a granite-water interface. Waves that propagate along the free surface of a rock mass (surface waves) can severely hinder the detection of reflected events. Two methods of reducing this surface wave noise were investigated. The first technique uses physical obstructions (such as a slit trench) to scatter the surface waves. The second technique uses a linear array of receivers located on the free surface to cancel waves that are propagating parallel to the array (e.g., surface waves), thus enhancing waves with propagation vectors orthogonal to the linear array (e.g., reflected events). Deconvolution processing was found to be another method useful in surface wave cancellation

  15. Insight into subdecimeter fracturing processes during hydraulic fracture experiment in Äspö hard rock laboratory, Sweden

    Science.gov (United States)

    Kwiatek, Grzegorz; Martínez-Garzón, Patricia; Plenkers, Katrin; Leonhardt, Maria; Zang, Arno; Dresen, Georg; Bohnhoff, Marco

    2017-04-01

    We analyze the nano- and picoseismicity recorded during a hydraulic fracturing in-situ experiment performed in Äspö Hard Rock Laboratory, Sweden. The fracturing experiment included six fracture stages driven by three different water injection schemes (continuous, progressive and pulse pressurization) and was performed inside a 28 m long, horizontal borehole located at 410 m depth. The fracturing process was monitored with two different seismic networks covering a wide frequency band between 0.01 Hz and 100000 Hz and included broadband seismometers, geophones, high-frequency accelerometers and acoustic emission sensors. The combined seismic network allowed for detection and detailed analysis of seismicity with moment magnitudes MW<-4 (source sizes approx. on cm scale) that occurred solely during the hydraulic fracturing and refracturing stages. We relocated the seismicity catalog using the double-difference technique and calculated the source parameters (seismic moment, source size, stress drop, focal mechanism and seismic moment tensors). The physical characteristics of induced seismicity are compared to the stimulation parameters and to the formation parameters of the site. The seismic activity varies significantly depending on stimulation strategy with conventional, continuous stimulation being the most seismogenic. We find a systematic spatio-temporal migration of microseismic events (propagation away and towards wellbore injection interval) and temporal transitions in source mechanisms (opening - shearing - collapse) both being controlled by changes in fluid injection pressure. The derived focal mechanism parameters are in accordance with the local stress field orientation, and signify the reactivation of pre-existing rock flaws. The seismicity follows statistical and source scaling relations observed at different scales elsewhere, however, at an extremely low level of seismic efficiency.

  16. Coupled Modeling of Flow, Transport, and Deformation during Hydrodynamically Unstable Displacement in Fractured Rocks

    Science.gov (United States)

    Jha, B.; Juanes, R.

    2015-12-01

    Coupled processes of flow, transport, and deformation are important during production of hydrocarbons from oil and gas reservoirs. Effective design and implementation of enhanced recovery techniques such as miscible gas flooding and hydraulic fracturing requires modeling and simulation of these coupled proceses in geologic porous media. We develop a computational framework to model the coupled processes of flow, transport, and deformation in heterogeneous fractured rock. We show that the hydrocarbon recovery efficiency during unstable displacement of a more viscous oil with a less viscous fluid in a fractured medium depends on the mechanical state of the medium, which evolves due to permeability alteration within and around fractures. We show that fully accounting for the coupling between the physical processes results in estimates of the recovery efficiency in agreement with observations in field and lab experiments.

  17. Hydraulic and mechanical properties of natural fractures in low-permeability rock

    International Nuclear Information System (INIS)

    Pyrack-Nolte, L.J.; Myer, L.R.; Cook, N.G.W.; Witherspoon, P.A.

    1987-01-01

    The results of a comprehensive laboratory study of the mechanical displacement, permeability, and void geometry of single rock fractures in a quartz monzonite are summarized and analyzed. A metal-injection technique was developed that provided quantitative data on the precise geometry of the void spaces between the fracture surfaces and the areas of contact at different stresses. At effective stresses of less than 20 MPa fluid flow was proportional to the mean fracture aperture raised to a power greater than 3. As stress was increased, contact area was increased and void spaces become interconnected by small tortuous channels that constitute the principal impediment to fluid flow. At effective stresses higher than 20 MPa, the mean fracture aperture continued to diminish with increasing stress, but this had little effect on flow because the small tortuous flow channels deformed little with increasing stress

  18. Nuclide transport of decay chain in the fractured rock medium: a model using continuous time Markov process

    International Nuclear Information System (INIS)

    Younmyoung Lee; Kunjai Lee

    1995-01-01

    A model using continuous time Markov process for nuclide transport of decay chain of arbitrary length in the fractured rock medium has been developed. Considering the fracture in the rock matrix as a finite number of compartments, the transition probability for nuclide from the transition intensity between and out of the compartments is represented utilizing Chapman-Kolmogorov equation, with which the expectation and the variance of nuclide distribution for the fractured rock medium could be obtained. A comparison between continuous time Markov process model and available analytical solutions for the nuclide transport of three decay chains without rock matrix diffusion has been made showing comparatively good agreement. Fittings with experimental breakthrough curves obtained with nonsorbing materials such as NaLS and uranine in the artificial fractured rock are also made. (author)

  19. Understanding large scale groundwater flow in fractured crystalline rocks to aid in repository siting

    International Nuclear Information System (INIS)

    Davison, C.; Brown, A.; Gascoyne, M.; Stevenson, D.; Ophori, D.

    2000-01-01

    Atomic Energy of Canada Limited (AECL) conducted a ten-year long groundwater flow study of a 1050 km 2 region of fractured crystalline rock in southeastern Manitoba to illustrate how an understanding of large scale groundwater flow can be used to assist in selecting a hydraulically favourable location for the deep geological disposal of nuclear fuel waste. The study involved extensive field investigations that included the drilling testing, sampling and monitoring of twenty deep boreholes distributed at detailed study areas across the region. The surface and borehole geotechnical investigations were used to construct a conceptual model of the main litho-structural features that controlled groundwater flow through the crystalline rocks of the region. Eighty-three large fracture zones and other spatial domains of moderately fractured and sparsely fractured rocks were represented in a finite element model of the area to simulate regional groundwater flow. The groundwater flow model was calibrated to match the observed groundwater recharge rate and the hydraulic heads measured in the network of deep boreholes. Particle tracking was used to determine the pathways and travel times from different depths in the velocity field of the calibrated groundwater flow model. The results were used to identify locations in the regional flow field that maximize the time it takes for groundwater to travel to surface discharge areas through long, slow groundwater pathways. One of these locations was chosen as a good hypothetical location for situating a nuclear fuel waste disposal vault at 750 m depth. (authors)

  20. A new scripting library for modeling flow and transport in fractured rock with channel networks

    Science.gov (United States)

    Dessirier, Benoît; Tsang, Chin-Fu; Niemi, Auli

    2018-02-01

    Deep crystalline bedrock formations are targeted to host spent nuclear fuel owing to their overall low permeability. They are however highly heterogeneous and only a few preferential paths pertaining to a small set of dominant rock fractures usually carry most of the flow or mass fluxes, a behavior known as channeling that needs to be accounted for in the performance assessment of repositories. Channel network models have been developed and used to investigate the effect of channeling. They are usually simpler than discrete fracture networks based on rock fracture mappings and rely on idealized full or sparsely populated lattices of channels. This study reexamines the fundamental parameter structure required to describe a channel network in terms of groundwater flow and solute transport, leading to an extended description suitable for unstructured arbitrary networks of channels. An implementation of this formalism in a Python scripting library is presented and released along with this article. A new algebraic multigrid preconditioner delivers a significant speedup in the flow solution step compared to previous channel network codes. 3D visualization is readily available for verification and interpretation of the results by exporting the results to an open and free dedicated software. The new code is applied to three example cases to verify its results on full uncorrelated lattices of channels, sparsely populated percolation lattices and to exemplify the use of unstructured networks to accommodate knowledge on local rock fractures.

  1. A new method for real-time monitoring of grout spread through fractured rocks

    International Nuclear Information System (INIS)

    Henderson, A. E.; Robertson, I. A.; Whitfield, J. M.; Garrard, G. F. G.; Swannell, N. G.; Fisch, H.

    2008-01-01

    Reducing water ingress into the Shaft at Dounreay is essential for the success of future intermediate level waste (ILW) recovery using the dry retrieval method. The reduction is being realised by forming an engineered barrier of ultrafine cementitious grout injected into the fractured rock surrounding the Shaft. Grout penetration of 6 m in <50μm fractures is being reliably achieved, with a pattern of repeated injections ultimately reducing rock mass permeability by up to three orders of magnitude. An extensive field trials period, involving over 200 grout mix designs and the construction of a full scale demonstration barrier, has yielded several new field techniques that improve the quality and reliability of cementitious grout injection for engineered barriers. In particular, a new method has been developed for tracking in real-time the spread of ultrafine cementitious grout through fractured rock and relating the injection characteristics to barrier design. Fieldwork by the multi-disciplinary international team included developing the injection and real-time monitoring techniques, pre- and post injection hydro-geological testing to quantify the magnitude and extent of changes in rock mass permeability, and correlation of grout spread with injection parameters to inform the main works grouting programme. (authors)

  2. Flexible parallel implicit modelling of coupled thermal–hydraulic–mechanical processes in fractured rocks

    Directory of Open Access Journals (Sweden)

    M. Cacace

    2017-09-01

    Full Text Available Theory and numerical implementation describing groundwater flow and the transport of heat and solute mass in fully saturated fractured rocks with elasto-plastic mechanical feedbacks are developed. In our formulation, fractures are considered as being of lower dimension than the hosting deformable porous rock and we consider their hydraulic and mechanical apertures as scaling parameters to ensure continuous exchange of fluid mass and energy within the fracture–solid matrix system. The coupled system of equations is implemented in a new simulator code that makes use of a Galerkin finite-element technique. The code builds on a flexible, object-oriented numerical framework (MOOSE, Multiphysics Object Oriented Simulation Environment which provides an extensive scalable parallel and implicit coupling to solve for the multiphysics problem. The governing equations of groundwater flow, heat and mass transport, and rock deformation are solved in a weak sense (either by classical Newton–Raphson or by free Jacobian inexact Newton–Krylow schemes on an underlying unstructured mesh. Nonlinear feedbacks among the active processes are enforced by considering evolving fluid and rock properties depending on the thermo-hydro-mechanical state of the system and the local structure, i.e. degree of connectivity, of the fracture system. A suite of applications is presented to illustrate the flexibility and capability of the new simulator to address problems of increasing complexity and occurring at different spatial (from centimetres to tens of kilometres and temporal scales (from minutes to hundreds of years.

  3. Hydraulic fracturing rock stress measurement at Haestholmen, Finland

    International Nuclear Information System (INIS)

    Ljunggren, C.; Klasson, H.

    1992-12-01

    This report presents hydraulic fracturing measurements in two boreholes located on the Haestholmen island near Loviisa, Finland. The aim of the measurements was to provide stress data, forming input for the design of an underground facility for disposal of low- and medium-level waste as well as future plant decommissioning radioactive waste from the IVO reactor units situated on Haestholmen. The theoretical background to the hydrofracturing method is summarized, as is the equipment and experimental procedures used in the present case. All results obtained are presented and critically discussed. The final stress parameters presented are magnitudes and directions of the maximum and minimum horizontal stresses. Testing was successfully completed according to schedule in both boreholes.(orig.)

  4. Healing of shear strength and its time dependency in a single rock fracture

    International Nuclear Information System (INIS)

    Kawaguchi, Yuta; Nakashima, Shinichiro; Yasuhara, Hideaki; Kishida, Kiyoshi

    2011-01-01

    Evolution of the long-term mechanical, hydraulic, and transport characteristics of rock fractures should be, in advance, predicted in considering an issue on entombment of energy byproducts of high level radioactive wastes. Under stressed and temperature conditions, those behaviors of the rock fractures of interest may be evolved in time and space likely due to the change in topographical aperture distributions. This irreversible process may be induced by pure mechanical and/or chemo-mechanical creeps such as water-rock reactions like stress corrosion and pressure solution, and chemical effects including mineral dissolution and reprecipitation in the free-walls of fractures. Specifically, the chemo-mechanical processes active at the contacting asperities within rock fractures may exert a significant influence on the mechanical, hydraulic, and transport behaviors throughout a long period, and thus, should be vigorously examined theoretically and experimentally. This paper presents the slide-hold-slide shear test results for fully saturated, single-jointed mortar specimens so as to investigate the effects of load holding on mechanical properties of rock joints. From the test results, it was confirmed that shear strength increased for mortar specimens in both short and long time holding cases. However, the evolution of shear strength recovery in two cases is different. This is because a dominant factor of shear strength recovery during the short time holding may be attributed to a pure mechanical process like creep deformation at contacting asperities, while the one during long time holding is affected by both mechanical and chemical processes like pressure solution. Moreover, to reproduce the shear strength recovery during short time holding we develop a direct shear model by including temporal variation of dilation during holding. The model predictions are in relatively good agreement with the test measurements. (author)

  5. Coupled hydromechanical paleoclimate analyses of density-dependant groundwater flow in discretely fractured crystalline rock settings

    Science.gov (United States)

    Normani, S. D.; Sykes, J. F.; Jensen, M. R.

    2009-04-01

    A high resolution sub-regional scale (84 km2) density-dependent, fracture zone network groundwater flow model with hydromechanical coupling and pseudo-permafrost, was developed from a larger 5734 km2 regional scale groundwater flow model of a Canadian Shield setting in fractured crystalline rock. The objective of the work is to illustrate aspects of regional and sub-regional groundwater flow that are relevant to the long-term performance of a hypothetical nuclear fuel repository. The discrete fracture dual continuum numerical model FRAC3DVS-OPG was used for all simulations. A discrete fracture zone network model delineated from surface features was superimposed onto an 789887 element flow domain mesh. Orthogonal fracture faces (between adjacent finite element grid blocks) were used to best represent the irregular discrete fracture zone network. The crystalline rock between these structural discontinuities was assigned properties characteristic of those reported for the Canadian Shield at the Underground Research Laboratory at Pinawa, Manitoba. Interconnectivity of permeable fracture features is an important pathway for the possibly relatively rapid migration of average water particles and subsequent reduction in residence times. The multiple 121000 year North American continental scale paleoclimate simulations are provided by W.R. Peltier using the University of Toronto Glacial Systems Model (UofT GSM). Values of ice sheet normal stress, and proglacial lake depth from the UofT GSM are applied to the sub-regional model as surface boundary conditions, using a freshwater head equivalent to the normal stress imposed by the ice sheet at its base. Permafrost depth is applied as a permeability reduction to both three-dimensional grid blocks and fractures that lie within the time varying permafrost zone. Two different paleoclimate simulations are applied to the sub-regional model to investigate the effect on the depth of glacial meltwater migration into the subsurface. In

  6. Characterizing fractured plutonic rocks of the Canadian shield for deep geological disposal of Canada's radioactive wastes

    International Nuclear Information System (INIS)

    Lodha, G.S.; Davison, C.C.; Gascoyne, M.

    1998-01-01

    Since 1978 AECL has been investigating plutonic rocks of the Canadian Shield as a potential medium for the disposal of Canada's nuclear fuel waste. During the last two years this study has been continued as part of Ontario Hydro's used fuel disposal program. Methods have been developed for characterizing the geotechnical conditions at the regional scale of the Canadian Shield as well as for characterizing conditions at the site scale and the very near-field scale needed for locating and designing disposal vault rooms and waste emplacement areas. The Whiteshell Research Area (WRA) and the Underground Research Laboratory (URL) in southeastern Manitoba have been extensively used to develop and demonstrate the different scales of characterization methods. At the regional scale, airborne magnetic and electromagnetic surveys combined with LANDSAT 5 and surface gravity survey data have been helpful in identifying boundaries of the plutonic rocks , overburden thicknesses, major lineaments that might be geological structures, lithological contacts and depths of the batholiths. Surface geological mapping of exposed rock outcrops, combined with surface VLF/EM, radar and seismic reflection surveys were useful in identifying the orientation and depth continuity of low-dipping fracture zones beneath rock outcrops to a depth of 500 to 1000 m. The surface time-domain EM method has provided encouraging results for identifying the depth of highly saline pore waters. The regional site scale investigations at the WRA included the drilling of twenty deep boreholes (> 500 m) at seven separate study areas. Geological core logging combined with borehole geophysical logging, TV/ATV logging, flowmeter logging and full waveform sonic logging in these boreholes helped to confirm the location of hydro geologically important fractures, orient cores and infer the relative permeability of some fracture zones. Single-hole radar and crosshole seismic tomography surveys were useful to establish the

  7. Consideration on the Mechanism of Microwave Emission Due to Rock Fracture

    Science.gov (United States)

    Takano, Tadashi; Sugita, Seiji; Yoshida, Shingo; Maeda, Takashi

    2010-05-01

    Microwave emission due to rock fracture was found at 300 MHz, 2 GHz, and 22 GHz, and its power was calibrated in laboratory for the first time in the world. The observed waveform is impulsive, and contains correspondent frequency component inside the envelope at each frequency band. At such high frequencies, the electro-magnetic signal power can be calibrated as a radiating wave with high accuracy. Accordingly, it was verified that a substantial power is emitted. The microwave emission phenomena were also observed on occasions of hypervelocity impact, and esteemed as phenomena generally associated with material destruction. Earthquakes and volcanic activities are association with rock fractures so that the microwave is expected to be emitted. Actually, the e emission was confirmed by the data analysis of the brightness temperature obtained by a remote sensing satellite, which flew over great earthquakes of Wuenchan and Sumatra, and great volcanic eruptions of Reventador and Chanten. It is important to show the microwave emission during rock fracture in natural phenomena. Therefore, the field test to detect the microwave due to the collapse of a crater cliff was planned and persecuted at the volcano of Miyake-jima about 100 km south of Tokyo. Volcanic activity may be more convenient than an earthquake because of the known location and time. As a result, they observed the microwave emission which was strongly correlated with the cliff collapses. Despite of the above-mentioned phenomenological fruits, the reason of the microwave emission is not fixed yet. We have investigated the mechanism of the emission in consideration of the obtained data in rock fracture experiments so far and the study results on material destruction by hypervelocity impact. This paper presents the proposal of the hypothesis and resultant discussions. The microwave sensors may be useful to monitor natural hazards such as an earthquake or a volcanic eruption, because the microwave due to rock

  8. A study on the ground water flow and hydrogeochemical interaction in fractured rock masses

    International Nuclear Information System (INIS)

    Ahn, Jong Sung; Kim, Chun Soo; Yoon, Si Tae; Kim, Sun Joon; Chung, Chan Ho; Kim, Gye Nam

    1991-01-01

    A study site, the Precambrian gneiss complex in the vincinity of Chungyang has been investigated by geologic surface mapping, tunnel mapping and core drilling with chemical analysis and microscopic observation of rock samples and fracture filling materials. Four boreholes at depths between 50 and 200m were drilled. They are located in a potential fracture zone, which was selected based on the topographic characterisitcs and the fracture survey data. The hydraulic characteristics are described based on the results of constant pressure injection test and cross hole test. In the single hole test, the test sections varied between 1 and 5 m. The hydraulic conductivity of local fracture zones ranges from 1xlO -5 to lxlO -7 m/sec whereas that of the intact rock within the depth of 50 m is in the range of 7xlO -8 to 8xlO -9 m/sec. The field dispersivity values obtained from an injection phase range from 0.15 to 4.5 m at varying depths. The whole thickness dispersivity on the 18 m section obtained from a withdrawal phase is 0.4 m. The dispersion test in two well non-circulation mode was carried out along a single fracture set at depth between 11.5-14.5m. The longitudinal dispersivity obtained from the two well test is 8.14 m. The identified minerals of host rocks are quartz, K-feldspar,plagioclase, biotite, muscovite, sericite, chlorite, calcite, pyrite, zircon and opaque minerals. The primary minerals such as feldspar and biotite are highly altered into sericite and chlorite respectively. The fracture-filling materials from core samples identified by as calcite, kaolinite, smectite, chlorite, illitite, quartz, pyrite with fe- and Mn-oxides. (Author)

  9. Analysis of the hydraulic data from the MI fracture zone at the Grimsel Rock Laboratory, Switzerland

    International Nuclear Information System (INIS)

    Davey, A.; Karasaki, K.; Long, J.C.S.; Landsfeld, M.; Mensch, A.; Martel, S.J.

    1989-10-01

    One of the major problems in analyzing flow and transport in fractured rock is that the flow may be largely confined to a poorly connected network of fractures. In order to overcome some of this problem, Lawrence Berkeley Laboratory (LBL) has been developing a new type of fracture hydrology model called an equivalent discontinuum model. In this model the authors represent the discontinuous nature of the problem through flow on a partially filled lattice. A key component in constructing an equivalent discontinuum model from this lattice is removing some of the conductive elements such that the system is partially connected in the same manner as the fracture network. This is done through a statistical inverse technique called simulated annealing. The fracture network model is annealed by continually modifying a base model, or template such that the modified systems behave more and more like the observed system. In order to see how the simulated annealing algorithm works, the authors have developed a series of synthetic real cases. In these cases, the real system is completely known so that the results of annealing to steady state data can be evaluated absolutely. The effect of the starting configuration has been studied by varying the percent of conducting elements in the initial configuration. Results have shown that the final configurations converge to about the same percentage of conducting elements. An example using Nagra field data from the Migration Experiment (MI) at Grimsel Rock Laboratory in Switzerland is also analyzed. 24 refs., 33 figs., 3 tabs

  10. Colloid-facilitated radionuclide transport in the fractured rock: effects of decay chain and limited matrix diffusion

    International Nuclear Information System (INIS)

    Park, J. B.; Park, J. W.; Lee, E. Y.; Kim, C. R.

    2002-01-01

    Colloid-facilitated radionuclide transport in the fractured rock is studies by considering radioactive decay chain and limited matrix diffusion into surrounding porous media. Semi-analytical solution in the Laplace domain is obtained from the mass balance equation of radionuclides and colloid particles. Numerical inversion of the Laplace solution is used to get the concentration profiles both in a fracture and in rock matrix. There issues are analyzed for the radionuclide concentration in a fracture by 1) formation constant of pseudo-colloid, 2) filtration coefficient of radio-colloid and 3) effective diffusion depth into the surrounding porous rock media

  11. Groundwater degassing and two-phase flow in fractured rock: Summary of results and conclusions achieved during the period 1994-2000

    International Nuclear Information System (INIS)

    Jarsjoe, J.; Destouni, G.

    2001-06-01

    Although water saturated conditions generally prevail several hundreds of metres below the ground water table, two-phase flow conditions, i.e. a mixed flow of gas and water, may develop in the vicinity of a repository situated in a regionally saturated rock mass. Deep groundwater naturally contains dissolved gases that may come out of solution if the water pressure is reduced to atmospheric pressure in the vicinity of boreholes and drifts, for instance, during hydraulic and tracer testing. Under certain conditions, this may lead to development of an unsaturated zone, affecting the local hydrology. Other possible sources of two-phase flow conditions in the vicinity of a deep repository include air entry in connection with tunnel ventilation and gas generation in the repository due to corrosion or biological processes. Quantitative two-phase flow models are needed in order to investigate the potential effects of all the above processes. However, traditional constitutive relations for two-phase/unsaturated flow were developed for porous media and are based on parameters that can be readily estimated in soil, but are difficult or impossible to determine independently in fractured rock. Despite the parameter estimation difficulties, several studies have indicated that these relations can be calibrated to reproduce observed unsaturated fracture flow behaviour. In this report, we show that a novel, fractured rock relation is at least equally capable of calibrated reproduction of unsaturated fracture flow as the widely used van Genuchten relation for porous media. Moreover, due to the fact that the novel relation is based on parameters that are physically relevant for (and independently measurable in) rock fractures in the field, it has the potential of independent prediction capabilities, which is not the case for the van Genuchten relation. We furthermore consider in detail the effects of groundwater degassing on measurements of hydraulic properties in boreholes and

  12. Single well injection withdrawal tests (SWIW) in fractured rock. Some aspects on interpretation

    International Nuclear Information System (INIS)

    Neretnieks, Ivars

    2007-08-01

    Single-Well-Injection-Withdrawal, SWIW, tests are used to try to extract information on fracture apertures, sorption and diffusion properties and dispersion information in individual fractures. It is done by injecting a given amount of traced water into an isolated fracture. After a waiting period water is withdrawn from the fracture and the tracer concentration is measured. The concentration time curve is fitted to a model and the parameter values quantifying the different interaction mechanisms are determined. A number of different mechanisms influence the recovery of the tracer. One or more of the following mechanisms are considered. They include: dispersion due to velocity differences, sorption on fracture surface and on infill, diffusion in rock fragments in the fracture, diffusion between 'streamlines', diffusion into rock matrix and other stagnant water volumes, sorption kinetics and slow drift of the plume caused by the natural gradient. Many of the interaction mechanisms can influence the recovery curve in a similar way. For example, diffusion into rock matrix water and into stagnant water in the fracture adjacent to the flowing channels cannot be distinguished if only one tracer is used. Tracers with different properties can in principle be used but they will encounter different parts of the fracture, the sorbing tracer will move out less from the injection point than a nonsorbing tracer will. Diffusion and sorption in small particles in the flowpath can influence the recovery curve in a similar way as rock matrix diffusion does. Dispersion caused by diffusion between 'streamlines', Taylor dispersion, can give very different results in channels of different shapes. Such dispersion effects can be difficult to distinguish from matrix diffusion effects. Dispersion coefficients obtained in a SWIW test may have little relation to dispersion of a tracer moving from A to B. This is partly due to the different mechanisms and partly due to different time scales

  13. Single well injection withdrawal tests (SWIW) in fractured rock. Some aspects on interpretation

    Energy Technology Data Exchange (ETDEWEB)

    Neretnieks, Ivars [Dept. of Chemical Engineering and Technology, Royal Inst. of Technology, Stockholm (Sweden)

    2007-08-15

    Single-Well-Injection-Withdrawal, SWIW, tests are used to try to extract information on fracture apertures, sorption and diffusion properties and dispersion information in individual fractures. It is done by injecting a given amount of traced water into an isolated fracture. After a waiting period water is withdrawn from the fracture and the tracer concentration is measured. The concentration time curve is fitted to a model and the parameter values quantifying the different interaction mechanisms are determined. A number of different mechanisms influence the recovery of the tracer. One or more of the following mechanisms are considered. They include: dispersion due to velocity differences, sorption on fracture surface and on infill, diffusion in rock fragments in the fracture, diffusion between 'streamlines', diffusion into rock matrix and other stagnant water volumes, sorption kinetics and slow drift of the plume caused by the natural gradient. Many of the interaction mechanisms can influence the recovery curve in a similar way. For example, diffusion into rock matrix water and into stagnant water in the fracture adjacent to the flowing channels cannot be distinguished if only one tracer is used. Tracers with different properties can in principle be used but they will encounter different parts of the fracture, the sorbing tracer will move out less from the injection point than a nonsorbing tracer will. Diffusion and sorption in small particles in the flowpath can influence the recovery curve in a similar way as rock matrix diffusion does. Dispersion caused by diffusion between 'streamlines', Taylor dispersion, can give very different results in channels of different shapes. Such dispersion effects can be difficult to distinguish from matrix diffusion effects. Dispersion coefficients obtained in a SWIW test may have little relation to dispersion of a tracer moving from A to B. This is partly due to the different mechanisms and partly due to

  14. Water level fluctuations due to earth tides in a well pumping from slightly fractured crystalline rock

    International Nuclear Information System (INIS)

    Marine, I.W.

    1975-01-01

    J At the Savannah River plant of the Atomic Energy Commission near Aiken, South Carolina, there are three distinct groundwater systems: the coastal plain sediments, the crystalline metamorphic rocks, and a buried Triassic basin. The coastal plain sediments include several Cretaceous and Tertiary granular aquifers and aquicludes, the total thickness being about 305 m. Below these sediments, water occurs in small fractures in crystalline metamorphic rock (hornblende schist and gneiss with lesser amounts of quartzite). Water level fluctuations due to earth tides are recorded in the crystalline metamorphic rock system and in the coastal plain sediments. No water level fluctuations due to earth tides have been observed in wells in the Triassic rock because of the very low permeability. The water level fluctuations due to earth tides in the crystalline rock are about 10 cm, and those in the sediments are about 1.8 cm. The use of water level fluctuations due to earth tides to calculate porosity appears to present practical difficulties both in the crystalline metamorphic rock system and in the coastal plain sediments. In a 1-yr pumping test on a well in the crystalline metamorphic rock the flow was controlled to within 0.1 percent of the total discharge, which was 0.94 1/s. The water level fluctuations due to earth tides in the pumping well were 10 cm, the same as when this well was not being pumped. (U.S.)

  15. The impact of a (hyper)alkaline plume on (fractured) crystalline rock

    International Nuclear Information System (INIS)

    Alexander, Russell

    2012-01-01

    Russell Alexander from Bedrock Geosciences, Switzerland, gave a presentation on the possible effects of cement pore waters on a crystalline host rock. Field, laboratory and natural analogue studies as well as geochemical modelling indicate that cement leachates tend to induce the sealing of fractures in the rock. These studies also indicate that strongly alkaline waters might: - Accelerate the dissolution of vitrified waste, but probably not affect the dissolution rate of spent fuel. - Degrade bentonite to some degree. To avoid some of the effects associated with the use of concrete, several approaches may be used: - Minimisation and tracking/monitoring of the concrete masses. - Development and use of low-pH cements and alternative grouting materials. - The selection of less fractured rock volumes for a repository location. The sealing of fractures evidenced in the Maquarin natural analogue study might contribute to limiting the extent of perturbations caused by an alkaline plume and is likely to create a hydraulic barrier that affects groundwater flow. The effects of these processes should be analysed in a safety case since they may support the idea of a self-sealing repository. Uncertainties in the treatment of an alkaline plume in fractured rock include: - The possible formation of colloids. - Thermodynamic data for cement components and secondary mineral stability. - Cement carbonation. - The effects of super-plasticisers. Given these uncertainties, current assessments of perturbations around a HLW or spent fuel repository caused by cementitious materials are often conservative and provide a pessimistic view of disposal system performance. Discussion of the paper included: Will groundwater flows in deep systems be fast enough to cause pervasive sealing of fractures? The process of how a network of fractures may be sealed over time is uncertain. The flow field will be altered as fractures are sealed and this may cause flow rates in other parts of the fracture

  16. Sealing of rock fractures around HLW repositories, 2

    International Nuclear Information System (INIS)

    Chigira, Masahiro

    1993-01-01

    During the flow of a silica-saturated hydrothermal solution in rock with negative temperature gradients, the behavior of silica in such solution is controlled by temperature, temperature gradient, pH, flow velocity, and solid surface area/fluid mass ratio (A/M). Such behavior could not be analysed precisely and totally at present state, but 'threshold conditions' have been found experimentally, under which solution keeps in equilibrium with solid silica in a flow field with temperature gradients. Solution keeps in equilibrium with solid silica under the conditions of A/M ratios more than 700 m 2 /kg, temperatures 80 - 120degC, temperature gradients less than 50degC/m, and pH 6 - 9, if mean pore velocities are less than 100 m/y. Under the same A/M ratios, temperature gradients, and pH, mean pore velocities must be less than 5 m/y in order to keep solution in equilibrium with solid silica in a flow field with temperatures 80 - 25degC. These 'threshold conditions' are expected to be satisfied in a near field of a repository of high-level radioactive waste, which suggests that if a groundwater is once saturated with silica under a higher temperature in a near field it would flow with decreasing temperatures in equilibrium with solid silica. In this case, the precipitation rate of amorphous silica along the flow path can be estimated without kinetic consideration. (author) 54 refs

  17. An integrated geophysical and hydraulic investigation to characterize a fractured-rock aquifer, Norwalk, Connecticut

    Science.gov (United States)

    Lane, J.W.; Williams, J.H.; Johnson, C.D.; Savino, D.M.; Haeni, F.P.

    2002-01-01

    The U.S. Geological Survey conducted an integrated geophysical and hydraulic investigation at the Norden Systems, Inc. site in Norwalk, Connecticut, where chlorinated solvents have contaminated a fractured-rock aquifer. Borehole, borehole-to-borehole, surface-geophysical, and hydraulic methods were used to characterize the site bedrock lithology and structure, fractures, and transmissive zone hydraulic properties. The geophysical and hydraulic methods included conventional logs, borehole imagery, borehole radar, flowmeter under ambient and stressed hydraulic conditions, and azimuthal square-array direct-current resistivity soundings. Integrated interpretation of geophysical logs at borehole and borehole-to-borehole scales indicates that the bedrock foliation strikes northwest and dips northeast, and strikes north-northeast to northeast and dips both southeast and northwest. Although steeply dipping fractures that cross-cut foliation are observed, most fractures are parallel or sub-parallel to foliation. Steeply dipping reflectors observed in the radar reflection data from three boreholes near the main building delineate a north-northeast trending feature interpreted as a fracture zone. Results of radar tomography conducted close to a suspected contaminant source area indicate that a zone of low electromagnetic (EM) velocity and high EM attenuation is present above 50 ft in depth - the region containing the highest density of fractures. Flowmeter logging was used to estimate hydraulic properties in the boreholes. Thirty-three transmissive fracture zones were identified in 11 of the boreholes. The vertical separation between transmissive zones typically is 10 to 20 ft. Open-hole and discrete-zone transmissivity was estimated from heat-pulse flowmeter data acquired under ambient and stressed conditions. The open-hole transmissivity ranges from 2 to 86 ft2/d. The estimated transmissivity of individual transmissive zones ranges from 0.4 to 68 ft2/d. Drawdown monitoring

  18. Summary of three dimensional pump testing of a fractured rock aquifer in the western Siberian Basin

    International Nuclear Information System (INIS)

    Nichols, R.L.; Looney, B.B.; Eddy-Dilek, C.A.; Drozhko, E.G.; Glalolenko, Y.V.; Mokrov, Y.G.; Ivanov, I.A.; Glagolev, A.V.; Vasil'kova, N.A.

    1996-01-01

    A group of scientists from the Savannah River Technology Center and Russia successfully completed a 17 day field investigation of a fractured rock aquifer at the MAYAK PA nuclear production facility in Russia. The test site is located in the western Siberian Basin near the floodplain of the Mishelyak river. The fractured rock aquifer is composed of orphyrites, tuff, tuffbreccia and lava and is overlain by 0.5--12 meters of elluvial and alluvial sediments. A network of 3 uncased wells (176, 1/96, and 2/96) was used to conduct the tests. Wells 176 and 2/96 were used as observation wells and the centrally located well 1/96 was used as the pumping well. Six packers were installed and inflated in each of the observation wells at a depth of up to 85 meters. The use of 6 packers in each well resulted in isolating 7 zones for monitoring. The packers were inflated to different pressures to accommodate the increasing hydrostatic pressure. A straddle packer assembly was installed in the pumping well to allow testing of each of the individual zones isolated in the observation wells. A constant rate pumping test was run on each of the 7 zones. The results of the pumping tests are included in Appendix A. The test provided new information about the nature of the fractured rock aquifers in the vicinity of the Mishelyak river and will be key information in understanding the behavior of contaminants originating from process wastes discharged to Lake Karachi. Results from the tests will be analyzed to determine the hydraulic properties of different zones within the fractured rock aquifer and to determine the most cost effective clean-up approach for the site

  19. State of the art of numerical modeling of thermohydrologic flow in fractured rock mass

    International Nuclear Information System (INIS)

    Wang, J.S.Y.; Tsang, C.F.; Sterbentz, R.A.

    1983-01-01

    The state of the art of numerical modeling of thermohydrologic flow in fractured rock masses is reviewed and a comparative study is made of several models which have been developed in nuclear waste isolation, geothermal energy, ground-water hydrology, petroleum engineering, and other geologic fields. The general review is followed by separate summaries of the main characteristics of the governing equations, numerical solutions, computer codes, validations, and applications for each model

  20. The state of the art of numerical modeling of thermohydrologic flow in fractured rock masses

    International Nuclear Information System (INIS)

    Wang, J.S.Y.; Sterbentz, R.A.; Tsang, C.F.

    1982-01-01

    The state of the art of numerical modeling of thermohydrologic flow in fractured rock masses is reviewed and a comparative study is made of several models which have been developed in nuclear waste isolation, geothermal energy, ground water hydrology, petroleum engineering, and other geologic fields. The general review is followed by individual summaries of each model and the main characteristics of its governing equations, numerical solutions, computer codes, validations, and applications

  1. Numerical Study of Critical Role of Rock Heterogeneity in Hydraulic Fracture Propagation

    Energy Technology Data Exchange (ETDEWEB)

    J. Zhou; H. Huang; M. Deo

    2016-03-01

    Log and seismic data indicate that most shale formations have strong heterogeneity. Conventional analytical and semi-analytical fracture models are not enough to simulate the complex fracture propagation in these highly heterogeneous formation. Without considering the intrinsic heterogeneity, predicted morphology of hydraulic fracture may be biased and misleading in optimizing the completion strategy. In this paper, a fully coupling fluid flow and geomechanics hydraulic fracture simulator based on dual-lattice Discrete Element Method (DEM) is used to predict the hydraulic fracture propagation in heterogeneous reservoir. The heterogeneity of rock is simulated by assigning different material force constant and critical strain to different particles and is adjusted by conditioning to the measured data and observed geological features. Based on proposed model, the effects of heterogeneity at different scale on micromechanical behavior and induced macroscopic fractures are examined. From the numerical results, the microcrack will be more inclined to form at the grain weaker interface. The conventional simulator with homogeneous assumption is not applicable for highly heterogeneous shale formation.

  2. On the description of the properties of fractured rock using the concept of a porous medium

    International Nuclear Information System (INIS)

    Stokes, J.

    1980-05-01

    In order to describe the flow of groundwater through fractured rock, water is either assumed to flow through a pervious continuum of through descrete fractures between impervious blocks of rock. The latter approach being the one demanding more information on the rock, problems on groundwater flow are usually discussed using the porous medium approach. It is often a question of debate wether the continuum approach is applicable to the fractured rock under consideration. Therefore, it is essential that after assuming that a certain flow region acts as a porous medium, we use a procedure for measuring the properties that at the same time gives a test of this assumption. When giving a description of groundwater flow, the goal is often a presentation of pathlines and flowtimes between points of interest and the ground surface. Using a porous medium approach, this means that hydraulic conductivity and porosity must be known through the medium. In order to cope with transient flow, we must also know the time constant governing the development of the flow. The pathlines depend to a great extent on the variation of conductivity through space. A conductivity decreasing with depth will force the pathlines to the surface giving local flow. If instead the conductivity is constant, the flow is regional. It is therefore important to know the gradient of hydraulic conductivity. Finally, as we know that the flow takes place through a geological structure, the anisotropic behaviour of the rock must be known in order to describe the flow. In this report a procedure to measure the properties listed above is developed. (author)

  3. Clay club initiative: self-healing of fractures in clay-rich host rocks

    International Nuclear Information System (INIS)

    Horseman, S.T.; Cuss, R.J.; Reeves, H.J.

    2004-01-01

    The capacity of fractures in argillaceous rocks to self-heal (or become, with the passage of time, less conductive to groundwater) is often cited as a primary factor favouring the choice of such materials as host rocks for deep disposal. The underlying processes which contribute to self-healing can be broadly subdivided into: (a) mechanical and hydro-mechanical processes linked to the change in the stress field, movement of pore water, swelling, softening, plastic deformation and creep, and (b) geochemical processes linked to chemical alterations, transport in aqueous solution and the precipitation of minerals. Since chemical alteration can cause profound changes to the mechanical properties of argillaceous rocks, it is often difficult to draw a firm line between these two subdivisions. Based on the deliberations of the recent Cluster Conference in Luxembourg, there would appear to be some support for the use of the term 'self-sealing' for processes affecting fracture conductivity in argillaceous rock that are largely mechanical or hydro-mechanical in their origin. There are four main areas in which the self-healing capacity of the host rock becomes relevant to repository design and performance assessment: - potential for radionuclide transport within the excavation damage zone (EDZ); - design and performance of repository sealing systems; - potential impact of gas migration; - long-term performance considering erosional unloading, seismicity and fault reactivation. The presence of an EDZ is acknowledged to be a particularly important issue in performance assessment. Interconnection of fractures in the EDZ could lead to the development of a preferential flow path extending along the emplacement holes, access tunnels and shafts of a repository towards overlying aquifers and the biosphere. In the preliminary French Safety Analyses, for example, the treatment of scenarios relating to early seal failure have highlighted the hydraulic role of the damaged zone as a

  4. Fractal Characteristics of Rock Fracture Surface under Triaxial Compression after High Temperature

    Directory of Open Access Journals (Sweden)

    X. L. Xu

    2016-01-01

    Full Text Available Scanning Electron Microscopy (SEM test on 30 pieces of fractured granite has been researched by using S250MK III SEM under triaxial compression of different temperature (25~1000°C and confining pressure (0~40 MPa. Research results show that (1 the change of fractal dimension (FD of rock fracture with temperature is closely related to confining pressure, which can be divided into two categories. In the first category, when confining pressure is in 0~30 MPa, FD fits cubic polynomial fitting curve with temperature, reaching the maximum at 600°C. In the second category, when confining pressure is in 30~40 MPa, FD has volatility with temperature. (2 The FD of rock fracture varies with confining pressure and is also closely related to the temperature, which can be divided into three categories. In the first category, FD has volatility with confining pressure at 25°C, 400°C, and 800°C. In the second category, it increases exponentially at 200°C and 1000°C. In the third category, it decreases exponentially at 600°C. (3 It is found that 600°C is the critical temperature and 30 MPa is the critical confining pressure of granite. The rock transfers from brittle to plastic phase transition when temperature exceeds 600°C and confining pressure exceeds 30 MPa.

  5. CRYSTAL: A model of a fractured rock geosphere for performance assessment within SKI Project-90

    International Nuclear Information System (INIS)

    Worgan, K.; Robinson, P.

    1992-02-01

    A one-dimensional model of a fractured rock geosphere (CRYSTAL) has been developed, which forms part of the toolkit for the Swedish Nuclear Power Inspectorates reference repository performance assessment programme (Project-90). CRYSTAL predicts the transport of arbitrary-length decay chains by advection, diffusion and surface sorption in the fractures and sideways diffusion into the rock matrix. The model equations are solved in Laplace transform space, and inverted numerically to the time domain. This approach avoids time-stepping and consequently is numerically very efficient. The interface of CRYSTAL with the time-series output from a near-field model, such as CALIBRE, is achieved using the method of convolution. The response of the geosphere to delta-function inputs from each nuclide is combined with the time series outputs from the near-field, to obtain the nuclide flux emerging from the far-field. The method is sufficiently flexible to allow for any general time-series input from CALIBRE or any other near-field model. Although CRYSTAL was developed to handle one-dimensional transport in a fractured rock, the equations solved are sufficiently general for it to be used in other applications, e.g. in a porous system. (au)

  6. Colloid facilitated transport in fractured rocks: parameter estimation and comparison with experimental data

    International Nuclear Information System (INIS)

    Viswanthan, H.S.; Wolfsberg, A.V.; Reimus, P.W.; Ware, D.; Lu, G.

    2003-01-01

    Colloid-facilitated migration of plutonium in fractured rock has been implicated in both field and laboratory studies. Other reactive radionuclides may also experience enhanced mobility due to groundwater colloids. Model prediction of this process is necessary for assessment of contaminant boundaries in systems for which radionuclides are already in the groundwater and for performance assessment of potential repositories for radioactive waste. Therefore, a reactive transport model is developed and parameterized using results from controlled laboratory fracture column experiments. Silica, montmorillonite and clinoptilolite colloids are used in the experiments along with plutonium and Tritium. The goal of the numerical model is to identify and parameterize the physical and chemical processes that affect the colloid-facilitated transport of plutonium in the fractures. The parameters used in this model are similar in form to those that might be used in a field-scale transport model

  7. Radionuclide migration in fractured rock: hydrological investigations at an experimental site in the Carnmennellis granite, Cornwall

    International Nuclear Information System (INIS)

    Heath, M.J.; Durrance, E.M.

    1985-01-01

    The objectives, methods and results of hydrological investigation of the granite at an experimental site in Cornwall are described and discussed. Constant head injection tests and radioactive tracer experiments have revealed a fracture permeability in which water movement is confined to discrete fractures separated by rock of very low permeability. Data on flow path frequency, orientation and effective hydraulic aperture, required for network modelling, are presented for a 700 m borehole, with additional hydraulic data from three other boreholes. In addition to fractures of average hydraulic conductivity a small number of major hydraulic features (''main drains'') with major implications for radionuclide migration have been identified. A mean hydraulic conductivity for the granite investigated of 1.57x10 -7 ms -1 has been obtained, 2.11x10 -8 ms -1 if the major hydraulic features are excluded

  8. Innovations in the characterization of fractured rocks developed within the Stripa project

    International Nuclear Information System (INIS)

    Black, J.; Brightman, M.; Holmes, D.

    1994-01-01

    This text deals with the hydrogeological work that has been carried out at Stripa Mine. First of all, the philosophy applied evolved through the years, and has finally been focused on a fractured rock approach. Second, it has been necessary to develop hydraulic testing methods - such as focused packer testing - and equipment; the key of the success of the equipment that was built, was that it was fully computer controlled and able to regulate water pressures quickly, reliably and accurately. In the end, the aim of the hydrogeological testing was to characterize both the small scale fracture network and the large scale major fracture zone which composed the site. (TEC). 13 refs., 5 figs

  9. Laboratory studies of groundwater degassing in replicas of natural fractured rock for linear flow geometry

    International Nuclear Information System (INIS)

    Geller, J.T.

    1998-02-01

    Laboratory experiments to simulate two-phase (gas and water) flow in fractured rock evolving from groundwater degassing were conducted in transparent replicas of natural rock fractures. These experiments extend the work by Geller et al. (1995) and Jarsjo and Geller (1996) that tests the hypothesis that groundwater degassing caused observed flow reductions in the Stripa Simulated Drift Experiment (SDE). Understanding degassing effects over a range of gas contents is needed due to the uncertainty in the gas contents of the water at the SDE. The main objectives of this study were to: (1) measure the effect of groundwater degassing on liquid flow rates for lower gas contents than the values used in Geller for linear flow geometry in the same fracture replicas of Geller; (2) provide a data set to develop a predictive model of two-phase flow in fractures for conditions of groundwater degassing; and (3) improve the certainty of experimental gas contents (this effort included modifications to the experimental system used by Geller et al. and separate gas-water equilibration tests). The Stripa site is being considered for a high-level radioactive waste repository

  10. Bioremediation in fractured rock: 1. Modeling to inform design, monitoring, and expectations

    Science.gov (United States)

    Tiedeman, Claire; Shapiro, Allen M.; Hsieh, Paul A.; Imbrigiotta, Thomas; Goode, Daniel J.; Lacombe, Pierre; DeFlaun, Mary F.; Drew, Scott R.; Johnson, Carole D.; Williams, John H.; Curtis, Gary P.

    2018-01-01

    Field characterization of a trichloroethene (TCE) source area in fractured mudstones produced a detailed understanding of the geology, contaminant distribution in fractures and the rock matrix, and hydraulic and transport properties. Groundwater flow and chemical transport modeling that synthesized the field characterization information proved critical for designing bioremediation of the source area. The planned bioremediation involved injecting emulsified vegetable oil and bacteria to enhance the naturally occurring biodegradation of TCE. The flow and transport modeling showed that injection will spread amendments widely over a zone of lower‐permeability fractures, with long residence times expected because of small velocities after injection and sorption of emulsified vegetable oil onto solids. Amendments transported out of this zone will be diluted by groundwater flux from other areas, limiting bioremediation effectiveness downgradient. At nearby pumping wells, further dilution is expected to make bioremediation effects undetectable in the pumped water. The results emphasize that in fracture‐dominated flow regimes, the extent of injected amendments cannot be conceptualized using simple homogeneous models of groundwater flow commonly adopted to design injections in unconsolidated porous media (e.g., radial diverging or dipole flow regimes). Instead, it is important to synthesize site characterization information using a groundwater flow model that includes discrete features representing high‐ and low‐permeability fractures. This type of model accounts for the highly heterogeneous hydraulic conductivity and groundwater fluxes in fractured‐rock aquifers, and facilitates designing injection strategies that target specific volumes of the aquifer and maximize the distribution of amendments over these volumes.

  11. Three-Dimensional Geostatistical Analysis of Rock Fracture Roughness and Its Degradation with Shearing

    Directory of Open Access Journals (Sweden)

    Nima Babanouri

    2013-12-01

    Full Text Available Three-dimensional surface geometry of rock discontinuities and its evolution with shearing are of great importance in understanding the deformability and hydro-mechanical behavior of rock masses. In the present research, surfaces of three natural rock fractures were digitized and studied before and after the direct shear test. The variography analysis of the surfaces indicated a strong non-linear trend in the data. Therefore, the spatial variability of rock fracture surfaces was decomposed to one deterministic component characterized by a base polynomial function, and one stochastic component described by the variogram of residuals. By using an image-processing technique, 343 damaged zones with different sizes, shapes, initial roughness characteristics, local stress fields, and asperity strength values were spatially located and clustered. In order to characterize the overall spatial structure of the degraded zones, the concept of ‘pseudo-zonal variogram’ was introduced. The results showed that the spatial continuity at the damage locations increased due to asperity degradation. The increase in the variogram range was anisotropic and tended to be higher in the shear direction; thus, the direction of maximum continuity rotated towards the shear direction. Finally, the regression-kriging method was used to reconstruct the morphology of the intact surfaces and degraded areas. The cross-validation error of interpolation for the damaged zones was found smaller than that obtained for the intact surface.

  12. The Fracture Influence on the Energy Loss of Compressed Air Energy Storage in Hard Rock

    Directory of Open Access Journals (Sweden)

    Hehua Zhu

    2015-01-01

    Full Text Available A coupled nonisothermal gas flow and geomechanical numerical modeling is conducted to study the influence of fractures (joints on the complex thermohydromechanical (THM performance of underground compressed air energy storage (CAES in hard rock caverns. The air-filled chamber is modeled as porous media with high porosity, high permeability, and high thermal conductivity. The present analysis focuses on the CAES in hard rock caverns at relatively shallow depth, that is, ≤100 m, and the pressure in carven is significantly higher than ambient pore pressure. The influence of one discrete crack and multiple crackson energy loss analysis of cavern in hard rock media are carried out. Two conditions are considered during each storage and release cycle, namely, gas injection and production mass being equal and additional gas injection supplemented after each cycle. The influence of the crack location, the crack length, and the crack open width on the energy loss is studied.

  13. Characterization of Gas Transport Properties of Fractured Rocks By Borehole and Chamber Tests.

    Science.gov (United States)

    Shimo, M.; Shimaya, S.; Maejima, T.

    2014-12-01

    Gas transport characteristics of fractured rocks is a great concern to variety of engineering applications such as underground storage of LPG, nuclear waste disposal, CCS and gas flooding in the oil field. Besides absolute permeability, relative permeability and capillary pressure as a function of water saturation have direct influences to the results of two phase flow simulation. However, number of the reported gas flow tests for fractured rocks are limited, therefore, the applicability of the conventional two-phase flow functions used for porous media, such as Mualem-van Genuchten model, to prediction of the gas transport in the fractured rock mass are not well understood. The authors conducted the two types of in-situ tests, with different scales, a borehole gas-injection test and a chamber gas-injection test in fractured granitic rock. These tests were conducted in the Cretaceous granitic rocks at the Namikata underground LPG storage cavern construction site in Ehime Prefecture in Japan, preceding to the cavern scale gas-tightness test. A borehole injection test was conducted using vertical and sub-vertical boreholes drilled from the water injection tunnel nearly at the depth of the top of the cavern, EL-150m. A new type downhole gas injection equipment that is capable to create a small 'cavern' within a borehole was developed. After performing a series of preliminary tests to investigate the hydraulic conductivity and gas-tightness, i.e. threshold pressure, gas injection tests were conducted under different gas pressure. Fig.1 shows an example of the test results From a chamber test using a air pressurizing chamber with volume of approximately166m3, the gas-tightness was confirmed within the uncertainty of 22Pa under the storage pressure of 0.7MPa, however, significant air leakage occurred possibly through an open fracture intersecting the chamber just after cavern pressure exceeds the initial hydrostatic pressure at the ceiling level of the chamber. Anomalies

  14. The motion of a redox front in a system of bentonite and rock, incorporating fracture transport effects

    International Nuclear Information System (INIS)

    Shaw, W.; Robinson, P.

    1992-02-01

    This report presents new calculations of the motion of a redox front in a system of bentonite and fractured rock, incorporation advection and diffusion of oxidants in fracture water. The results reported here have been incorporated into preliminary base case calculations using the source term model CALIBRE. The model presented here differs mainly in its treatment of the effects of the fracture. Previously, a 'zero-concentration' boundary condition was applied, and this resulted in retardation of the front near the fracture. When a more detailed advection-diffusion model is applied, the front is advanced in a neighbourhood of the fracture. (25 refs.) (au)

  15. Fracture Dissolution of Carbonate Rock: An Innovative Process for Gas Storage

    Energy Technology Data Exchange (ETDEWEB)

    James W. Castle; Ronald W. Falta; David Bruce; Larry Murdoch; Scott E. Brame; Donald Brooks

    2006-10-31

    The goal of the project is to develop and assess the feasibility and economic viability of an innovative concept that may lead to commercialization of new gas-storage capacity near major markets. The investigation involves a new approach to developing underground gas storage in carbonate rock, which is present near major markets in many areas of the United States. Because of the lack of conventional gas storage and the projected growth in demand for storage capacity, many of these areas are likely to experience shortfalls in gas deliverability. Since depleted gas reservoirs and salt formations are nearly non-existent in many areas, alternatives to conventional methods of gas storage are required. The need for improved methods of gas storage, particularly for ways to meet peak demand, is increasing. Gas-market conditions are driving the need for higher deliverability and more flexibility in injection/withdrawal cycling. In order to meet these needs, the project involves an innovative approach to developing underground storage capacity by creating caverns in carbonate rock formations by acid dissolution. The basic concept of the acid-dissolution method is to drill to depth, fracture the carbonate rock layer as needed, and then create a cavern using an aqueous acid to dissolve the carbonate rock. Assessing feasibility of the acid-dissolution method included a regional geologic investigation. Data were compiled and analyzed from carbonate formations in six states: Indiana, Ohio, Kentucky, West Virginia, Pennsylvania, and New York. To analyze the requirements for creating storage volume, the following aspects of the dissolution process were examined: weight and volume of rock to be dissolved; gas storage pressure, temperature, and volume at depth; rock solubility; and acid costs. Hydrochloric acid was determined to be the best acid to use because of low cost, high acid solubility, fast reaction rates with carbonate rock, and highly soluble products (calcium chloride

  16. Partitioning dynamics of unsaturated flows in fractured porous media: Laboratory studies and three-dimensional multi-scale smoothed particle hydrodynamics simulations of gravity-driven flow in fractures

    Science.gov (United States)

    Kordilla, J.; Bresinsky, L. T.; Shigorina, E.; Noffz, T.; Dentz, M.; Sauter, M.; Tartakovsky, A. M.

    2017-12-01

    Preferential flow dynamics in unsaturated fractures remain a challenging topic on various scales. On pore- and fracture-scales the highly erratic gravity-driven flow dynamics often provoke a strong deviation from classical volume-effective approaches. Against the common notion that flow in fractures (or macropores) can only occur under equilibrium conditions, i.e., if the surrounding porous matrix is fully saturated and capillary pressures are high enough to allow filling of the fracture void space, arrival times suggest the existence of rapid preferential flow along fractures, fracture networks, and fault zones, even if the matrix is not fully saturated. Modeling such flows requires efficient numerical techniques to cover various flow-relevant physics, such as surface tension, static and dynamic contact angles, free-surface (multi-phase) interface dynamics, and formation of singularities. Here we demonstrate the importance of such flow modes on the partitioning dynamics at simple fracture intersections, with a combination of laboratory experiments, analytical solutions and numerical simulations using our newly developed massively parallel smoothed particle hydrodynamics (SPH) code. Flow modes heavily influence the "bypass" behavior of water flowing along a fracture junction. Flows favoring the formation of droplets exhibit a much stronger bypass capacity compared to rivulet flows, where nearly the whole fluid mass is initially stored within the horizontal fracture. This behavior is demonstrated for a multi-inlet laboratory setup where the inlet-specific flow rate is chosen so that either a droplet or rivulet flow persists. The effect of fluid buffering within the horizontal fracture is presented in terms of dimensionless fracture inflow so that characteristic scaling regimes can be recovered. For both cases (rivulets and droplets), flow within the horizontal fracture transitions into a Washburn regime until a critical threshold is reached and the bypass efficiency

  17. Thermo-hydro-mechanical simulation of a 3D fractured porous rock: preliminary study of coupled matrix-fracture hydraulics

    Energy Technology Data Exchange (ETDEWEB)

    Canamon, I.; Javier Elorza, F. [Universidad Politecnica de Madrid, Dept. de Matematica Aplicada y Metodos Informaticas, ETSI Minas (UPM) (Spain); Ababou, R. [Institut de Mecanique des Fluides de Toulouse (IMFT), 31 (France)

    2007-07-01

    We present a problem involving the modeling of coupled flow and elastic strain in a 3D fractured porous rock, which requires prior homogenization (up-scaling) of the fractured medium into an equivalent Darcian anisotropic continuum. The governing equations form a system of PDE's (Partial Differential Equations) and, depending on the case being considered, this system may involve two different types of 'couplings' (in a real system, both couplings (1) and (2) generally take place): 1) Hydraulic coupling in a single (no exchange) or in a dual matrix-fracture continuum (exchange); 2) Thermo-Hydro-Mechanical interactions between fluid flow, pressure, elastic stress, strain, and temperature. We present here a preliminary model and simulation results with FEMLAB{sup R}, for the hydraulic problem with anisotropic heterogeneous coefficients. The model is based on data collected at an instrumented granitic site (FEBEX project) for studying a hypothetical nuclear waste repository at the Grimsel Test Site in the Swiss Alps. (authors)

  18. VSP in crystalline rocks - from downhole velocity profiling to 3-D fracture mapping

    International Nuclear Information System (INIS)

    Cosma, C.; Heikkinen, P.; Keskinen, J.; Enescu, N.

    1998-01-01

    VSP surveys have been carried out at several potential nuclear waste disposal sites in Finland since the mid 80s. To date, more than 200 three-component profiles have been measured. The main purpose of the surveys was to detect fracture zones in the crystalline bedrock and to determine their position. Most seismic events could be linked to zones of increased fracturing observed in the borehole logs. The more pronounced seismic reflectors could be correlated with hydrogeologically significant zones, which have been the main targets in the investigations. Processing and interpretation methods have been developed specifically for VSP surveys in crystalline rocks: Weak reflections from thin fracture zones are enhanced by multi-channel filtering techniques based on the Radon transform. The position and orientation of the fracture zones are determined by polarisation analysis and by combining data from several shot points. The compilation of the results from several boreholes gives a comprehensive image of the fracture zones at the scale of the whole site. The discussion of the methodology is based on examples from the Olkiluoto site, in SW Finland

  19. Joint seismic, hydrogeological, and geomechanical investigations of a fracture zone in the Grimsel Rock Laboratory, Switzerland

    International Nuclear Information System (INIS)

    Majer, E.L.; Myer, L.R.; Peterson, J.E. Jr.; Karasaki, K.; Long, J.C.S.; Martel, S.J.; Bluemling, P.; Vomvoris, S.

    1990-06-01

    This report is one of a series documenting the results of the Nagra-DOE Cooperative (NDC-I) research program in which the cooperating scientists explore the geological, geophysical, hydrological, geochemical, and structural effects anticipated from the use of a rock mass as a geologic repository for nuclear waste. From 1987 to 1989 the United States Department of Energy (DOE) and the Swiss Cooperative for the Storage of Nuclear Waste (Nagra) participated in an agreement to carryout experiments for understanding the effect of fractures in the storage and disposal of nuclear waste. As part of this joint work field and laboratory experiments were conducted at a controlled site in the Nagra underground Grimsel test site in Switzerland. The primary goal of these experiments in this fractured granite was to determine the fundamental nature of the propagation of seismic waves in fractured media, and to relate the seismological parameters to the hydrological parameters. The work is ultimately aimed at the characterization and monitoring of subsurface sites for the storage of nuclear waste. The seismic experiments utilizes high frequency (1000 to 10,000 Hertz) signals in a cross-hole configuration at scales of several tens of meters. Two-, three-, and four-sided tomographic images of the fractures and geologic structure were produced from over 60,000 raypaths through a 10 by 21 meter region bounded by two nearly horizontal boreholes and two tunnels. Intersecting this region was a dominant fracture zone which was the target of the investigations. In addition to these controlled seismic imaging experiments, laboratory work using core from this region were studied for the relation between fracture content, saturation, and seismic velocity and attenuation. In-situ geomechanical and hydrologic tests were carried out to determine the mechanical stiffness and conductivity of the fractures. 20 refs., 90 figs., 6 tabs

  20. A genetic meta-algorithm-assisted inversion approach: hydrogeological study for the determination of volumetric rock properties and matrix and fluid parameters in unsaturated formations

    Science.gov (United States)

    Szabó, Norbert Péter

    2018-03-01

    An evolutionary inversion approach is suggested for the interpretation of nuclear and resistivity logs measured by direct-push tools in shallow unsaturated sediments. The efficiency of formation evaluation is improved by estimating simultaneously (1) the petrophysical properties that vary rapidly along a drill hole with depth and (2) the zone parameters that can be treated as constant, in one inversion procedure. In the workflow, the fractional volumes of water, air, matrix and clay are estimated in adjacent depths by linearized inversion, whereas the clay and matrix properties are updated using a float-encoded genetic meta-algorithm. The proposed inversion method provides an objective estimate of the zone parameters that appear in the tool response equations applied to solve the forward problem, which can significantly increase the reliability of the petrophysical model as opposed to setting these parameters arbitrarily. The global optimization meta-algorithm not only assures the best fit between the measured and calculated data but also gives a reliable solution, practically independent of the initial model, as laboratory data are unnecessary in the inversion procedure. The feasibility test uses engineering geophysical sounding logs observed in an unsaturated loessy-sandy formation in Hungary. The multi-borehole extension of the inversion technique is developed to determine the petrophysical properties and their estimation errors along a profile of drill holes. The genetic meta-algorithmic inversion method is recommended for hydrogeophysical logging applications of various kinds to automatically extract the volumetric ratios of rock and fluid constituents as well as the most important zone parameters in a reliable inversion procedure.

  1. Dynamic seismic signatures of saturated porous rocks containing two orthogonal sets of fractures: theory versus numerical simulations

    Science.gov (United States)

    Guo, Junxin; Rubino, J. Germán; Glubokovskikh, Stanislav; Gurevich, Boris

    2018-05-01

    The dispersion and attenuation of seismic waves are potentially important attributes for the non-invasive detection and characterization of fracture networks. A primary mechanism for these phenomena is wave-induced fluid flow (WIFF), which can take place between fractures and their embedding background (FB-WIFF), as well as within connected fractures (FF-WIFF). In this work, we propose a theoretical approach to quantify seismic dispersion and attenuation related to these two manifestations of WIFF in saturated porous rocks permeated by two orthogonal sets of fractures. The methodology is based on existing theoretical models for rocks with aligned fractures, and we consider three types of fracture geometries, namely, periodic planar fractures, randomly spaced planar fractures and penny-shaped cracks. Synthetic 2-D rock samples with different degrees of fracture intersections are then explored by considering both the proposed theoretical approach and a numerical upscaling procedure that provides the effective seismic properties of generic heterogeneous porous media. The results show that the theoretical predictions are in overall good agreement with the numerical simulations, in terms of both the stiffness coefficients and the anisotropic properties. For the seismic dispersion and attenuation caused by FB-WIFF, the theoretical model for penny-shaped cracks matches the numerical simulations best, whereas for representing the effects due to FF-WIFF the periodic planar fractures model turns out to be the most suitable one. The proposed theoretical approach is easy to apply and is applicable not only to 2-D but also to 3-D fracture systems. Hence, it has the potential to constitute a useful framework for the seismic characterization of fractured reservoirs, especially in the presence of intersecting fractures.

  2. A critical review of the data requirements for fluid flow models through fractured rock

    International Nuclear Information System (INIS)

    Priest, S.D.

    1986-01-01

    The report is a comprehensive critical review of the data requirements for ten models of fluid flow through fractured rock, developed in Europe and North America. The first part of the report contains a detailed review of rock discontinuities and how their important geometrical properties can be quantified. This is followed by a brief summary of the fundamental principles in the analysis of fluid flow through two-dimensional discontinuity networks and an explanation of a new approach to the incorporation of variability and uncertainty into geotechnical models. The report also contains a review of the geological and geotechnical properties of anhydrite and granite. Of the ten fluid flow models reviewed, only three offer a realistic fracture network model for which it is feasible to obtain the input data. Although some of the other models have some valuable or novel features, there is a tendency to concentrate on the simulation of contaminant transport processes, at the expense of providing a realistic fracture network model. Only two of the models reviewed, neither of them developed in Europe, have seriously addressed the problem of analysing fluid flow in three-dimensional networks. (author)

  3. Analysis of the behavior of radionuclides migration in fractured medium in different types of rocks matrices

    International Nuclear Information System (INIS)

    Sá, Ludimila Silva Salles de; Silveira, Cláudia Siqueira da; Lima, Zelmo Rodrigues de

    2017-01-01

    In management of radioactive wastes, the current trend is to dispose the radioactive waste for long life and high activity in permanent repositories of depth, geologically stable and low permeability. Thus, it is relevant to analyze the groundwater movement process, because the mechanism by which the radionuclides in a repository with fractures could return to the surface would be through the groundwater circulation system. A common problem encountered is the modeling of the migration of radionuclides in a fractured medium. The objective of this work is to evaluate the behavior of the migration of radionuclides in two types of rock matrix, considering the following properties: volumetric density, porosity, distribution coefficient and molecular diffusion coefficient. The physical system adopted consists of the matrix rock containing a discrete fracture in a porous medium saturated with water. The partial differential equations that describe the radionuclide movement were discretized by finite differences, and the Implicit Euler method was adopted. While for the convective term the numerical scheme of progressive differences was used

  4. Solute transport in a single fracture involving an arbitrary length decay chain with rock matrix comprising different geological layers.

    Science.gov (United States)

    Mahmoudzadeh, Batoul; Liu, Longcheng; Moreno, Luis; Neretnieks, Ivars

    2014-08-01

    A model is developed to describe solute transport and retention in fractured rocks. It accounts for advection along the fracture, molecular diffusion from the fracture to the rock matrix composed of several geological layers, adsorption on the fracture surface, adsorption in the rock matrix layers and radioactive decay-chains. The analytical solution, obtained for the Laplace-transformed concentration at the outlet of the flowing channel, can conveniently be transformed back to the time domain by the use of the de Hoog algorithm. This allows one to readily include it into a fracture network model or a channel network model to predict nuclide transport through channels in heterogeneous fractured media consisting of an arbitrary number of rock units with piecewise constant properties. More importantly, the simulations made in this study recommend that it is necessary to account for decay-chains and also rock matrix comprising at least two different geological layers, if justified, in safety and performance assessment of the repositories for spent nuclear fuel. Copyright © 2014 Elsevier B.V. All rights reserved.

  5. A multidisciplinary fractured rock characterization study at Raymond field site, Raymond, California

    International Nuclear Information System (INIS)

    Karasaki, Kenzi; Freifeld, Barry; Cohen, Andrew; Cook, Paul; Vasco, Don; Grossenbacher, Ken

    2001-01-01

    A dedicated field site was developed and a suite of experiments were conducted in the Sierra Nevada foothills, near the town of Raymond, California to develop and test a multi-disciplinary approach to the characterization of groundwater flow and transport in fractured rocks. A wealth of geologic, hydrologic and geophysical data was collected at the site using a variety of unique tools. A cluster of nine approximately 90 m deep boreholes were drilled at the site in a V-shaped pattern with an angle of 60 degrees. The boreholes are spaced 7.5, 15, 30, and 60 meters from the central borehole. Various geophysical and hydrologic tests were conducted in and between these boreholes. Integration of cross-hole radar and seismic tomography, borehole flow surveys and images from a new digital borehole scanner indicated that groundwater flow is mainly confined to a few sub-horizontal fracture zones. A unique suite of hydraulic tests were conducted, in which three to four intervals in each of the nine boreholes were isolated using pneumatic packers. Some 130 injection tests were conducted, and more than 4,100 cross-hole transient pressure measurements were obtained. A computer algorithm was developed to analyze such massive interference data systematically. As a result of the analysis, an image of the fracture connections emerged, which is consistent with the geophysical data. High precision tiltmeters were effective in remotely characterizing the preferential flow path. Several radial convergent tracer tests were conducted by injecting a mixture of several conservative tracers and one sorbing tracer: deuterium, fluorescein, lithium bromide and polystyrene micro-spheres. Some differences between the breakthrough curves are observed, which may be due to possible differences among so-called 'conservative' tracers. Some characterization tools were found to be more effective than others in locating flowing fractures. However, no single tool was almighty. Characterization of

  6. The Impact of Temperatures on the Stability of Rocks Surrounding a Single Fracture

    Science.gov (United States)

    Zhang, Yan; Li, Ning; Dai, Jun

    2018-05-01

    Research on the influence of temperature and the accompanying stress on the stability of the rocks surrounding an underground tunnel has become ever more important. This paper constructs a geometric model of a single-fracture tunnel by combining a high-temperature underground tunnel as the object of study with an example that uses a high-temperature tunnel segment in the water diversion tunnel of a hydropower station in Xinjiang. Based on the relevant theoretical analysis, with the consideration of different working conditions, a numerical experimental analysis was conducted to determine the two-dimensional transient temperature field distribution of the tunnel rock mass by using a numerical analysis software. The experimental data was consistent with the measured data. The calculated results show the following: a. when the temperature difference is greater, the stress concentration is higher near the fracture of the surrounding rock; b. the degree of the stress concentration in the crack tip region is not positively correlated to the distance, and there is a sensitive region where the stress varies.

  7. A Coupled Model for Natural Convection and Condensation in Heated Subsurface Enclosures Embedded in Fractured Rock

    International Nuclear Information System (INIS)

    Halecky, N.; Birkholzer, J.T.; Webb, S.W.; Peterson, P.F.; Bodvarsson, G.S.

    2006-01-01

    In heated tunnels such as those designated for emplacement of radioactive waste at Yucca Mountain, axial temperature gradients may cause natural convection processes that can significantly influence the moisture conditions in the tunnels and in the surrounding fractured rock. Large-scale convection cells would provide an effective mechanism for axial vapor transport, driving moisture out of the formation away from the heated tunnel section into cool end sections (where no waste is emplaced). To study such processes, we have developed and applied an enhanced version of TOUGH2 (Pruess et al., 1999) adding a new module that solves for natural convection in open cavities. The new TOUGH2 simulator simultaneously handles (1) the flow and energy transport processes in the fractured rock; (2) the flow and energy transport processes in the cavity; and (3) the heat and mass exchange at the rock-cavity interface. The new module is applied to simulate the future thermal-hydrological (TH) conditions within and near a representative waste emplacement tunnel at Yucca Mountain. Particular focus is on the potential for condensation along the emplacement section, a possible result of heat output differences between individual waste packages

  8. Quantifying Fracture Heterogeneity in Different Domains of Folded Carbonate Rocks to Improve Fractured Reservoir Analog Fluid Flow Models

    NARCIS (Netherlands)

    Bisdom, K.; Bertotti, G.; Gauthier, B.D.M.; Hardebol, N.J.

    2013-01-01

    Fluid flow in carbonate reservoirs is largely controlled by multiscale fracture networks. Significant variations of fracture network porosity and permeability are caused by the 3D heterogeneity of the fracture network characteristics, such as intensity, orientation and size. Characterizing fracture

  9. Quantifying Water-Rock Interactions during Hydraulic Fracturing from the Analysis of Flowback Water

    Science.gov (United States)

    Osselin, F.; Nightingale, M.; Kloppmann, W.; Gaucher, E.; Clarkson, C.; Mayer, B.

    2017-12-01

    Hydraulic fracturing technologies have facilitated the rapid development of shale gas and other unconventional resources throughout the world. In order to get sufficient access to the trapped hydrocarbon, it is necessary to fracture the bedrock and increase its permeability. Fracturing fluids are usually composed of tens of thousand of cubic meters of low salinity water with numerous additives, such as viscosity agent or breakers. The objective of this study was to investigate and quantify the water-rock interactions during hydraulic fracturing. This study was based on repeated sampling of flowback water from a hydraulically fractured well in Alberta, Canada. The flowback water was sampled 24 times during the first week and one last time after one, and analyzed for major ions and trace elements, as well as stable isotopes of sulfate and water among others. Results showed that salinity rapidly increases up to 100 000 mg/L at the end of the first week. We demonstrate that conservative species such as Na and Cl follow a clear two end-members mixing line, while some species including sulfate had much higher concentrations (8 times higher than the expected value from the mixing line). This indicates that the rapid increase of salinity in flowback water is caused by both mixing with formation water initially present in the shale formation, and from water-rock interactions triggered by the fracturing fluid and in some cases by the additives. Stable isotope data suggest that additional sulfate is mobilized as a consequence of pyrite oxidation, releasing sulfate, iron and potentially other heavy metals into the flowback water. This release of excess sulfate can be detrimental because it has the potential to promote scaling of sulfate minerals. Moreover, pyrite oxidation is a highly acidifying reaction and this may decrease the effectiveness of other additives, and promote carbonate minerals dissolution enhancing further scaling. We propose that a better control of the

  10. Secondary and tertiary gas injection in fractured carbonate rock: Experimental study

    Energy Technology Data Exchange (ETDEWEB)

    Karimaie, H.; Torsaeter, O. [SPE, NTNU (Norway); Darvish, G.R. [SPE, STATOIL (Norway); Lindeberg, E. [SPE, SINTEF (Norway)

    2008-09-15

    The use of CO{sub 2} has received considerable interest as a method of EOR but a major drawback is its availability and increasing cost. Therefore, as the number of CO{sub 2} injection projects increase, an alternative must be considered to meet the economic considerations. For this reason attention has been directed to nitrogen injection which may be a good substitute for CO{sub 2}. The purpose of the experiments described in this paper was to investigate the efficiency of oil recovery by CO{sub 2} and N{sub 2} in fractured carbonate rock. The combined effects of gravity drainage and component exchange between gas in fracture and oil in matrix on oil recovery in fractured reservoirs subjected to CO{sub 2} or nitrogen gas injection are experimentally studied. Laboratory experiments have been carried out on a low permeable outcrop chalk, as an analogue to a North Sea reservoir rock. This was surrounded by a fracture, established with a novel experimental set-up. The experiments aimed to investigate the potential of oil recovery by secondary and tertiary CO{sub 2} and nitrogen gas injection at high pressure high temperature condition. The matrix block was saturated using recombined binary mixture live oil (C{sub 1}-C{sub 7}), while the fracture was filled with a sealing material to obtain a homogeneous saturation. The sealing material was then removed by increasing the temperature which in turn creates the fracture surrounding the core. Gas was injected into the fracture at pressures above the bubble point of the oil. Oil recovery as a function of time was monitored during the experiments. Results from secondary gas injection experiments indicate that CO{sub 2} injection at elevated pressure and temperature is more efficient than N{sub 2} injection. Results from tertiary gas injection experiments also show that injection of CO{sub 2} could significantly recover the oil, even after waterflooding, compared to N{sub 2} injection. (author)

  11. Liquid infiltration through the boiling-point isotherm in a desiccating fractured rock matrix

    International Nuclear Information System (INIS)

    Phillips, O.M.

    1994-01-01

    Over a long time interval, the integrity of the radioactive waste repository proposed at Yucca Mountain may be compromised by corrosion accelerated by intermittent wetting which could occur by episodic infiltration of meteoric water from above through the fracture network. A simple two-dimensional model is constructed for the infiltration of liquid water down a fracture in a permeable rock matrix, beyond the boiling-point isotherm. The water may derive from episodic infiltration or from the condensation of steam above a desiccating region. Boiling of the water in the fracture is maintained by heat transfer from a surrounding superheated matrix blocks. There are two intrinsic length scales in this situation, (1): l s = ρ l q o L/(k m β) which is such that the total heat flow over this lateral distance balances that needed for evaporation of the liquid water infiltration, and (2): The thermal diffusion distance l θ = (k m t) 1/2 which increases with time after the onset of infiltration. The primary results are: (a) for two-dimensional infiltration down an isolated fracture or fault, the depth of penetration below the (undisturbed) boiling point isotherm is given by 1/2 π 1/2 (l s l θ ) 1/2 , and so increases as t 1/4 . Immediately following the onset of infiltration, penetration is rapid, but quickly slows. This behavior continues until l θ (and D) become comparable with l s . (b) With continuing infiltration down an isolated fracture or cluster of fractures, when l θ >> l s the temperature distribution becomes steady and the penetration distance stabilizes at a value proportional to l s . (c) Effects such as three-dimensionality of the liquid flow paths and flow rates, matrix infiltration, etc., appear to reduce the penetration distance

  12. Heat induced fracturing of rock in an existing uniaxial stress field

    International Nuclear Information System (INIS)

    Mathis, J.; Stephansson, O.; Bjarnason, B.; Hakami, H.; Herdocia, A.; Mattila, U.; Singh, U.

    1986-01-01

    This study was initiated under the premise that it may be possible to determine the state of stress in the earth's crust by heat induced fracturing of the rock surrounding a borehole. The theory involved is superficially simple, involving the superposition of the stress field around a borehole due to the existing virgin stresses and the uniform stress field of thermally loaded rock as induced by a heater. Since the heat stress field is uniform, varying only in magnitude and gradient as a function of heater input, fracturing should be controlled by the non-uniform virgin stress field. To determine if the method was, in fact, feasible, a series of laboratory test were conducted. These tests consisted of physically loading center drilled cubes of rock, 0.3 m on a side, uniaxially from 0 to 25 MPa. The blocks were then thermally loaded with a nominally rated 3.7 kW heater until failure occurred. Results from these laboratory tests were then compared to analytical studies of the problem, i.e., finite element and discrete theoretical analysis. Overall, results were such that the method is likely eliminated as a stress measurement technique. The immediate development of a thermal compressive zone on the borehole wall overlaps the tensile zone created by the uniaxial stress field, forcing the failure is thus controlled largely by the power input of the heater, being retarded by the small compressive stresses genrated by the uniaxial stress field. This small retardation effect is of such low magnitude that the retardation effect is of such low magnitude that the fracture time is relatively insensitive to the local virgin stress field. (authors)

  13. Fractured rock modeling in the National Waste Terminal Storage Program: a review of requirements and status

    International Nuclear Information System (INIS)

    St John, C.; Krug, A.; Key, S.; Monsees, J.

    1983-05-01

    Generalized computer codes capable of forming the basis for numerical models of fractured rock masses are being used within the NWTS program. Little additional development of these codes is considered justifiable, except in the area of representation of discrete fractures. On the other hand, model preparation requires definition of medium-specific constitutive descriptions and site characteristics and is therefore legitimately conducted by each of the media-oriented projects within the National Waste Terminal Storage program. However, it is essential that a uniform approach to the role of numerical modeling be adopted, including agreement upon the contribution of modeling to the design and licensing process and the need for, and means of, model qualification for particular purposes. This report discusses the role of numerical modeling, reviews the capabilities of several computer codes that are being used to support design or performance assessment, and proposes a framework for future numerical modeling activities within the NWTS program

  14. Non-Darcy Flow Experiments of Water Seepage through Rough-Walled Rock Fractures

    Directory of Open Access Journals (Sweden)

    Xiao-dong Ni

    2018-01-01

    Full Text Available The knowledge of flow phenomena in fractured rocks is very important for groundwater-resources management in hydrogeological engineering. The most commonly used tool to approximate the non-Darcy behavior of the flow velocity is the well-known Forchheimer equation, deploying the “inertial” coefficient β that can be estimated experimentally. Unfortunately, the factor of roughness is imperfectly considered in the literature. In order to do this, we designed and manufactured a seepage apparatus that can provide different roughness and aperture in the test; the rough fracture surface is established combining JRC and 3D printing technology. A series of hydraulic tests covering various flows were performed. Experimental data suggest that Forchheimer coefficients are to some extent affected by roughness and aperture. At last, favorable semiempirical Forchheimer equation which can consider fracture aperture and roughness was firstly derived. It is believed that such studies will be quite useful in identifying the limits of applicability of the well-known “cubic law,” in further improving theoretical/numerical models associated with fluid flow through a rough fracture.

  15. Analysis of hydromechanical well tests in fractured sedimentary rock at the NAWC site, New Jersey

    Science.gov (United States)

    Murdoch, L.C.; Hisz, D.B.; Ebenhack, J.F.; Fowler, D.E.; Tiedeman, C.R.; Germanovich, L.N.

    2009-01-01

    Hydromechanical well tests involve measuring and interpreting displacements along with hydraulic heads that result when a hydraulic stress is applied to a well. The motivation behind this type of test is that the displacement measurements provide information about the constitutive properties and structure of the aquifer that go beyond what can be derived from pressure signals alone. We used a borehole extensometer to measure transient displacements with a resolution of +/- 25 nm during well tests in fractured mudstone and sandstone at the former Naval Air Warfare Center in West Trenton, New Jersey. One well showed opening displacements on the order of 300nm during slug tests with maximum head changes of 7 m. Inversion of the transient signals suggest that a conductive fracture (aperture = 380 ??m, normal stiffness = 8??10 8 Pa/m) was largely responsible for the pressure signal, but the displacement signal appears to have resulted from both the fracture and deformation of the enveloping sandstone (E = 5 GPa, permeability = 0.6 md). At another well, an anomalous but repeatable signal was characterized by closing displacements during increasing pressure. This displacement signal can be explained by a hydraulically active fracture below the extensometer that became pressurized and compressed the overly sediments. Poroelastic theoretical analyses were inverted to estimate parameters and verify interpretations. Copyright 2009 ARMA, American Rock Mechanics Association.

  16. Laboratory experiments on heat-drive two-phase flows in natural and artificial rock fractures

    International Nuclear Information System (INIS)

    Kneafsey, Timothy J.; Pruess, Karsten

    1998-01-01

    Water flow in partially saturated fractures under thermal drive may lead to fast flow along preferential localized pathways and heat pipe conditions. At the potential high-level nuclear waste repository at Yucca Mountain, water flowing in fast pathways may ultimately contact waste packages and transport radionuclides to the accessible environment. Sixteen experiments were conducted to visualize heat-driven liquid flow in fracture models that included (1) assemblies of roughened glass plates, (2) epoxy replicas of rock fractures, and (3) a fractured specimen of Topopah Spring tuff. Continuous rivulet flow was observed for high liquid flow rates, intermittent rivulet flow and drop flow for intermediate flow rates, and film flow for lower flow rates and wide apertures. Heat pipe conditions (vapor-liquid counterflow with phase change) were identified in five of the seven experiments in which spatially resolved thermal monitoring was performed but not when vapor-liquid counterflow was hindered by very narrow apertures and when an inadequate working fluid volume was used

  17. Experimental and Numerical Investigations on Colloid-facilitated Plutonium Reactive Transport in Fractured Tuffaceous Rocks

    Science.gov (United States)

    Dai, Z.; Wolfsberg, A. V.; Zhu, L.; Reimus, P. W.

    2017-12-01

    Colloids have the potential to enhance mobility of strongly sorbing radionuclide contaminants in fractured rocks at underground nuclear test sites. This study presents an experimental and numerical investigation of colloid-facilitated plutonium reactive transport in fractured porous media for identifying plutonium sorption/filtration processes. The transport parameters for dispersion, diffusion, sorption, and filtration are estimated with inverse modeling for minimizing the least squares objective function of multicomponent concentration data from multiple transport experiments with the Shuffled Complex Evolution Metropolis (SCEM). Capitalizing on an unplanned experimental artifact that led to colloid formation and migration, we adopt a stepwise strategy to first interpret the data from each experiment separately and then to incorporate multiple experiments simultaneously to identify a suite of plutonium-colloid transport processes. Nonequilibrium or kinetic attachment and detachment of plutonium-colloid in fractures was clearly demonstrated and captured in the inverted modeling parameters along with estimates of the source plutonium fraction that formed plutonium-colloids. The results from this study provide valuable insights for understanding the transport mechanisms and environmental impacts of plutonium in fractured formations and groundwater aquifers.

  18. The Practical Application of Aqueous Geochemistry in Mapping Groundwater Flow Systems in Fractured Rock Masses

    Science.gov (United States)

    Bursey, G.; Seok, E.; Gale, J. E.

    2017-12-01

    Flow to underground mines and open pits takes place through an interconnected network of regular joints/fractures and intermediate to large scale structural features such as faults and fracture zones. Large scale features can serve either as high permeability pathways or as barriers to flow, depending on the internal characteristics of the structure. Predicting long term water quality in barrier-well systems and long-term mine water inflows over a mine life, as a mine expands, requires the use of a 3D numerical flow and transport code. The code is used to integrate the physical geometry of the fractured-rock mass with porosity, permeability, hydraulic heads, storativity and recharge data and construct a model of the flow system. Once that model has been calibrated using hydraulic head and permeability/inflow data, aqueous geochemical and isotopic data provide useful tools for validating flow-system properties, when one is able to recognize and account for the non-ideal or imperfect aspects of the sampling methods used in different mining environments. If groundwater samples are collected from discrete depths within open boreholes, water in those boreholes have the opportunity to move up or down in response to the forces that drive groundwater flow, whether they be hydraulic gradients, gas pressures, or density differences associated with variations in salinity. The use of Br/Cl ratios, for example, can be used to determine if there is active flow into, or out of, the boreholes through open discontinuities in the rock mass (i.e., short-circuiting). Natural groundwater quality can also be affected to varying degrees by mixing with drilling fluids. The combined use of inorganic chemistry and stable isotopes can be used effectively to identify dilution signals and map the dilution patterns through a range of fresh, brackish and saline water types. The stable isotopes of oxygen and hydrogen are nearly ideal natural tracers of water, but situations occur when deep

  19. Characterization and quantification of preferential flow in fractured rock systems, using resistivity tomography

    CSIR Research Space (South Africa)

    May, F

    2010-11-01

    Full Text Available , N Jovanovic2 and A Rozanov1 University of Stellenbosch1 and Council for Scientific and Industrial Research (CSIR)2 Characterization and quantification of preferential flow in fractured rock systems, using resistivity tomography Introduction... of slow and fast flowing pathways. Materials and Methods TABLE 1 DATE, TIME AND WEATHER CONDITIONS DURING RESISTIVITY TOMOGRAPHY SURVEY Survey No. Date Start time End time Precipitation (mm) Description KB001 8/27/2010 12H00 13H40 0.0 Sunny KB002 8...

  20. Displacement and stress fields around rock fractures opened by irregular overpressure variations

    Directory of Open Access Journals (Sweden)

    Shigekazu eKusumoto

    2014-05-01

    Full Text Available Many rock fractures are entirely driven open by fluids such as ground water, geothermal water, gas, oil, and magma. These are a subset of extension fractures (mode I cracks; e.g., dikes, mineral veins and joints referred to as hydrofractures. Field measurements show that many hydrofractures have great variations in aperture. However, most analytical solutions for fracture displacement and stress fields assume the loading to be either constant or with a linear variation. While these solutions have been widely used, it is clear that a fracture hosted by heterogeneous and anisotropic rock is normally subject to loading that is neither constant nor with a linear variation. Here we present new general solutions for the displacement and stress fields around hydrofractures, modelled as two-dimensional elastic cracks, opened by irregular overpressure variations given by the Fourier cosine series. Each solution has two terms. The first term gives the displacement and stress fields due to the average overpressure acting inside the crack; it is given by the initial term of the Fourier coefficients expressing the overpressure variation. The second term gives the displacement and stress fields caused by the overpressure variation; it is given by general terms of the Fourier coefficients and solved through numerical integration. Our numerical examples show that the crack aperture variation closely reflects the overpressure variation. Also, that the general displacement and stress fields close to the crack follow the overpressure variation but tend to be more uniform far from the crack. The present solutions can be used to estimate the displacement and stress fields around any fluid-driven crack, that is, any hydrofracture, as well as its aperture, provided the variation in overpressure can be described by Fourier series. The solutions add to our understanding of local stresses, displacements, and fluid transport associated with hydrofractures in the crust.

  1. Solute transport processes in a highly permeable fault zone of Lindau fractured rock test site (Germany)

    Energy Technology Data Exchange (ETDEWEB)

    Himmelsbach, T. [Ruhr-Univ., Bochum (Germany). Dept. of Applied Geology; Hoetzl, H. [Univ. of Karlsruhe (Germany). Dept. of Applied Geology; Maloszewski, P. [GSF-Inst. for Hydrology, Munich-Neuherberg (Germany)

    1998-09-01

    The results of field tracer experiments performed in the Lindau fractured rock test site (southern Black Forest, Germany) and subsequent modeling are presented. A vertical, hydrothermally mineralized fault zone, with a permeability much greater than the surrounding granite mass, lies beneath a planned dam site. A dense network of boreholes and tunnels were used to investigate scaling effects of solute transport processes in fractured rock. A series of tracer experiments using deuterium and dye tracers were performed over varying distances and under different testing procedures, resulting in different flow field conditions. Large-scale tracer experiments were performed under natural flow field conditions, while small-scale tracer experiments were performed under artificially induced radial-convergent and injection-withdrawal flow fields. The tracer concentration curves observed in all experiments were strongly influenced by the matrix diffusion. The curves were evaluated with the one-dimensional single fissure dispersion model (SFDM) adjusted for the different flow field conditions. The fitting model parameters found determined the fracture aperture, and matrix and fissure porosities. The determined fracture aperture varied between the sections having different hydraulic conductivity. The determined values of matrix porosity seemed to be independent of the scale of the experiment. The modeled matrix porosities agreed well with values determined in independent laboratory investigations of drill cores using mercury porosimetry. In situ fissure porosity, determined only in small-scale experiments, was independent of the applied geometry of the artificially induced flow fields. The dispersivities were found to be independent of the scale of experiment but dependent on the flow conditions. The values found in forced gradient tests lie between 0.2 and 0.3 m, while values in experiments performed under natural flow conditions were one order of magnitude higher.

  2. Hydrogeology of the unsaturated zone, Yucca Mountain, Nevada

    International Nuclear Information System (INIS)

    Montazer, P.; Wilson, W.E.

    1985-01-01

    The unsaturated volcanic tuff beneath Yucca Mountain, Nevada, is being evaluated by the US Department of Energy as a host rock for a potential mined geologic repository for high-level radioactive waste. Assessment of site suitability needs an efficient and focused investigative program. A conceptual hydrogeologic model that simulates the flow of fluids through the unsaturated zone at Yucca Mountain was developed to guide the program and to provide a basis for preliminary assessment of site suitability. The study was made as part of the Nevada Nuclear Waste Storage Investigations Project of the US Department of Energy. Thickness of the unsaturated zone is about 1640 to 2460 feet (500 to 750 meters). Based on physical properties, the rocks in the unsaturated zone are grouped for the purpose of this paper into five informal hydrogeologic units. From top to bottom these units are: Tiva Canyon welded unit, Paintbrush nonwelded unit. Topopah Spring welded unit, Calico Hills nonwelded unit, and Crater Flat unit. Welded units have a mean fracture density of 8 to 40 fractures per unit cubic meter, mean matrix porosities of 12 to 23%, matrix hydraulic conductivities with geometric means ranging from 6.5 x 10 -6 to 9.8 x 10 -6 foot per day (2 x 10 -6 to 3 x 10 -6 meter per day), and bulk hydraulic conductivities of 0.33 to 33 feet per day (0.1 to 10 meters per day). The nonwelded units have a mean fracture density of 1 to 3 fractures per unit cubic meter, mean matrix porosities of 31 to 46%, and saturated hydraulic conductivities with geometric means ranging from 2.6 x 10 -5 to 2.9 x 10 -2 foot per day (8 x 10 -6 to 9 x 10 -3 meter per day). 15 refs., 4 figs., 1 tab

  3. Preliminary analysis of the potential for thermally-induced rock fracture around high-level waste containers

    International Nuclear Information System (INIS)

    Ratigan, J.L.

    1976-01-01

    The major results are: the development of parametric formulations relating the potential for thermally induced fracturing in the high-level radioactive waste repository concept to the elastic and thermal properties of the site rock and the depth of the excavation, and the recognition of a need to determine the actual ''failure envelope'' for any potential site rock in the laboratory and adjust the parametric relations appropriately. Analysis of five rock types indicated that none would experience elastic/brittle failure due to the thermal stresses induced by the introduction of a 5 kW heat source. However, the rock strengths and elastic properties are laboratory values and not in situ values

  4. Characterizing and modelling the radionuclide transport properties of fracture zones in plutonic rocks of the Canadian Shield

    International Nuclear Information System (INIS)

    Davison, C.C.; Kozak, E.T.; Frost, L.H.; Everitt, R.A.; Brown, A.; Gascoyne, M.; Scheier, N.W.

    1999-01-01

    Plutonic rocks of the Canadian Shield were investigated as a potential host medium for nuclear fuel waste disposal of used CANDU nuclear fuel. Field investigations at several geologic research areas on the Shield have shown that major fracture zones are the dominant pathways for the large scale movement of groundwater and solutes through plutonic rock bodies. Because of this, a significant amount of the geoscience work has focused on methods to identify, characterize and model the radionuclide transport properties of major fracture zones in the fractured plutonic rocks of the Shield. In order to quantify the transport properties of such fracture zones a series of, groundwater tracer tests were performed over a period of several years in several major, low dipping fracture zones. Sixteen tracer tests were performed using dipole recirculation methods to evaluate transport over distance scales ranging from 17 m to 700 m. It was concluded that only tracer tests can provide useful estimates of the effective porosity and dispersivity characteristics of these large fracture zones in plutonic rocks of the Canadian Shield. (author)

  5. Evaluation of Low or High Permeability of Fractured Rock using Well Head Losses from Step-Drawdown Tests

    International Nuclear Information System (INIS)

    Kim, Byung Woo; Kim, Geon Young; Koh, Yong Kwon; Kim, Hyoung Soo

    2012-01-01

    The equation of the step-drawdown test 's w = BQ+CQ p ' written by Rorabaugh (1953) is suitable for drawdown increased non-linearly in the fractured rocks. It was found that value of root mean square error (RMSE) between observed and calculated drawdowns was very low. The calculated C (well head loss coefficient) and P (well head loss exponent) value of well head losses (CQ p ) ranged 3.689 x 10 -19 - 5.825 x 10 -7 and 3.459 - 8.290, respectively. It appeared that the deeper depth in pumping well the larger drawdowns due to pumping rate increase. The well head loss in the fractured rocks, unlike that in porous media, is affected by properties of fractures (fractures of aperture, spacing, and connection) around pumping well. The C and P value in the well head loss is very important to interpret turbulence interval and properties of high or low permeability of fractured rock. As a result, regression analysis of C and P value in the well head losses identified the relationship of turbulence interval and hydraulic properties. The relationship between C and P value turned out very useful to interpret hydraulic properties of the fractured rocks.

  6. Electromagnetic Emissions During Rock-fracturing Experiments Inside Magnetic Field Free Space

    Science.gov (United States)

    Wang, H.; Zhou, J.; Zhu, T.; Jin, H.

    2012-12-01

    Abnormal electromagnetic emission (EME) signal is one type of the most important precursors before earthquake, which has been widely observed and recorded before large earthquake, but the physical mechanism underlying the phenomenon is unclear and under controversy. Monitoring the EME signals during rock-fracturing experiments in laboratory is an effective way to study the phenomena and their underlying mechanism. Electromagnetic noise is everywhere because industrial and civilian electrical equipments have been widely used, which make difficulties to the in-lab experiments and field monitoring. To avoid the interference from electromagnetic noise, electromagnetic experiments must be carried out inside shielded space. Magnetic Field Free Space (MFFS) was constructed by Institute of Geophysics, China Earthquake Administration in 1980s. MFFS is a near-spherical polyhedron 'space' with 26 faces and inside diameter about 2.3 m. It is enclosed by 8-layer permalloy 1J85 for shielding magnetic field and 2-layer purified aluminium for shielding electric field. MFFS mainly shields static magnetic field by a factor of 160-4000 for the magnetic signals with the frequencies ranging from 0.01 Hz to 10 Hz. The intensity of magnetic field inside the space is less than 20 nT and its fluctuation is less than 0.3 nT in 90 hours. MFFS can dramatically shield EME signals in the frequency range of EME antennas utilized in our experiments, (several to ~320) kHz, by at least 90%, based on observation. Rock specimens (granite, marble) were fractured by two ways inside MFFS. 1) Cuboid bulk specimens were drilled, filled with static cracking agent, and then dilated from inside until fracture. 2) Cylindrical rock specimens were stressed until fracture by using a non-magnetic rock testing machine with the maximum testing force 300kN. EME, acoustic emission (AE) and strain signals were collected synchronously by the same data acquisitor, Acoustic Emission Workstation made by Physical Acoustics

  7. Self-sealing of excavation induced fractures in clay host rock

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Chun-Liang [Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) mbH, Braunschweig (Germany)

    2015-07-01

    Excavation of an underground repository for disposal of radioactive waste in clay formations generates fractures around the openings, which may act as pathways for water transport and radionuclides migration. Because of the favorable properties of the clay rocks such as the rheological deformability and swelling capability, a recovery process of the excavation damaged zone (EDZ) can be expected due to the combined impact of rock compression, backfill resistance, and clay swelling during the post-closure phase. Another important issue is the impact of gases produced from anoxic corrosion of waste containers and other metallic components within the repository. The EDZ may act as a conduit for preferential gas flow, depending on the extent of the recovery process. For the safety assessment of a repository, the self-sealing behaviour and impact on water and gas transport through the EDZ have to be characterized, understood, and predicted. Recently, GRS has extensively investigated these important issues with various kinds of laboratory and in- situ experiments under relevant repository conditions. Test samples were taken from the Callovo-Oxfordian argillite at Bure in France and the Opalinus clay (shaly facies) at Mont Terri in Switzerland. Major findings are summarized as follows. As observed in laboratory and in-situ, the gas permeabilities of the claystones increase with stress-induced damage by several orders of magnitude from the impermeable state up to high levels of 10{sup -12}-10{sup -13} m{sup 2}. When hydrostatic confining stress is applied and increased, the fractures in the claystones tend to close up, leading to a decrease in gas permeability down to different levels of 10{sup -16}-10{sup -21} m{sup 2} at stresses in a range of 10 to 20 MPa. As water enters and flows through fractures, the clay matrix can take up a great amount of the water and expand into the interstices. Consequently, the hydraulic conductivity decreases dramatically by several orders of

  8. Trends, prospects and challenges in quantifying flow and transport through fractured rocks

    Science.gov (United States)

    Neuman, Shlomo P.

    2005-03-01

    Among the current problems that hydrogeologists face, perhaps there is none as challenging as the characterization of fractured rock (Faybishenko and Benson 2000). This paper discusses issues associated with the quantification of flow and transport through fractured rocks on scales not exceeding those typically associated with single- and multi-well pressure (or flow) and tracer tests. As much of the corresponding literature has focused on fractured crystalline rocks and hard sedimentary rocks such as sandstones, limestones (karst is excluded) and chalk, so by default does this paper. Direct quantification of flow and transport in such rocks is commonly done on the basis of fracture geometric data coupled with pressure (or flow) and tracer tests, which therefore form the main focus. Geological, geophysical and geochemical (including isotope) data are critical for the qualitative conceptualization of flow and transport in fractured rocks, and are being gradually incorporated in quantitative flow and transport models, in ways that this paper unfortunately cannot describe but in passing. The hydrogeology of fractured aquifers and other earth science aspects of fractured rock hydrology merit separate treatments. All evidence suggests that rarely can one model flow and transport in a fractured rock consistently by treating it as a uniform or mildly nonuniform isotropic continuum. Instead, one must generally account for the highly erratic heterogeneity, directional dependence, dual or multicomponent nature and multiscale behavior of fractured rocks. One way is to depict the rock as a network of discrete fractures (with permeable or impermeable matrix blocks) and another as a nonuniform (single, dual or multiple) continuum. A third way is to combine these into a hybrid model of a nonuniform continuum containing a relatively small number of discrete dominant features. In either case the description can be deterministic or stochastic. The paper contains a brief assessment

  9. Permeability in fractured rocks from deep geothermal boreholes in the Upper Rhine Graben

    Science.gov (United States)

    Vidal, Jeanne; Whitechurch, Hubert; Genter, Albert; Schmittbuhl, Jean; Baujard, Clément

    2015-04-01

    Permeability in fractured rocks from deep geothermal boreholes in the Upper Rhine Graben Vidal J.1, Whitechurch H.1, Genter A.2, Schmittbuhl J.1, Baujard C.2 1 EOST, Université de Strasbourg 2 ES-Géothermie, Strasbourg The thermal regime of the Upper Rhine Graben (URG) is characterized by a series of geothermal anomalies on its French part near Soultz-sous-Forêts, Rittershoffen and in the surrounding area of Strasbourg. Sedimentary formations of these areas host oil field widely exploited in the past which exhibit exceptionally high temperature gradients. Thus, geothermal anomalies are superimposed to the oil fields which are interpreted as natural brine advection occurring inside a nearly vertical multi-scale fracture system cross-cutting both deep-seated Triassic sediments and Paleozoic crystalline basement. The sediments-basement interface is therefore very challenging for geothermal industry because most of the geothermal resource is trapped there within natural fractures. Several deep geothermal projects exploit local geothermal energy to use the heat or produce electricity and thus target permeable fractured rocks at this interface. In 1980, a geothermal exploration well was drilled close to Strasbourg down to the Permian sediments at 3220 m depth. Bottom hole temperature was estimated to 148°C but the natural flow rate was too low for an economic profitability (geothermal site by drilling five boreholes, three of which extend to 5 km depth. They identified a temperature of 200° C at 5 km depth in the granitic basement but with a variable flow rate. Hydraulic and chemical stimulation operations were applied in order to increase the initial low permeability by reactivating and dissolving sealed fractures in basement. The productivity was considerably improved and allows geothermal exploitation at 165° C and 20 L/s. Recent studies revealed the occurrences of permeable fractures in the limestones of Muschelkalk and the sandstones of Buntsandstein also. For

  10. Thermo-hydro-mechanical modelling of fractured rock masses application to radioactive wastes storage

    International Nuclear Information System (INIS)

    Vuillod, E.

    1995-01-01

    This work belongs to the Decovalex project (international cooperative project for the development of coupled models and their validation against experiments in nuclear waste isolation) of thermo-hydro-mechanical (THM) modeling of fractured rock massifs inside which high level radioactive waste disposal sites are simulated. The mathematical laws controlling the behaviour of the environment are resolved analytically in the case of a continuous environment (definition of an equivalent environment) and numerically if the environment is discontinuous (modeling of joints behaviour). The coupled THM models strongly influence the behaviour of a model. Modeling performed with the UDEC code shows the importance of HM couplings depending on whether the calculations are made in permanent or transient regime, and the influence of the loading path in the case of TM modeling. The geometry of fractures also influences the behaviour of the model. Studying the connexity of a fractures network allows to determine its degree of homogeneity. The comparison between two methods, continuous environment and discontinuous environment, has been carried out by determining the permeability tensor and the stress-deformation relations on fractured test-samples. It shows the differences in behaviour between an homogenized environment and a discrete environment. Finally two exercises of THM modeling of radioactive waste disposal sites illustrate the researches carried out. A far field model has permitted to compare the results obtained with calculation codes using different logics. The second model, a near field one, focusses more on the importance played by fracturing on the behaviour of the massif. The high density of the reference network has required some mathematical developments, in order to determine the representative equivalent volume (continuous approaches), and some mathematical analyses, to correctly simplify the environment (discontinuous approaches). These methods and analyses are

  11. Discrimination of Rock Fracture and Blast Events Based on Signal Complexity and Machine Learning

    Directory of Open Access Journals (Sweden)

    Zilong Zhou

    2018-01-01

    Full Text Available The automatic discrimination of rock fracture and blast events is complex and challenging due to the similar waveform characteristics. To solve this problem, a new method based on the signal complexity analysis and machine learning has been proposed in this paper. First, the permutation entropy values of signals at different scale factors are calculated to reflect complexity of signals and constructed into a feature vector set. Secondly, based on the feature vector set, back-propagation neural network (BPNN as a means of machine learning is applied to establish a discriminator for rock fracture and blast events. Then to evaluate the classification performances of the new method, the classifying accuracies of support vector machine (SVM, naive Bayes classifier, and the new method are compared, and the receiver operating characteristic (ROC curves are also analyzed. The results show the new method obtains the best classification performances. In addition, the influence of different scale factor q and number of training samples n on discrimination results is discussed. It is found that the classifying accuracy of the new method reaches the highest value when q = 8–15 or 8–20 and n=140.

  12. Effects of Host-rock Fracturing on Elastic-deformation Source Models of Volcano Deflation.

    Science.gov (United States)

    Holohan, Eoghan P; Sudhaus, Henriette; Walter, Thomas R; Schöpfer, Martin P J; Walsh, John J

    2017-09-08

    Volcanoes commonly inflate or deflate during episodes of unrest or eruption. Continuum mechanics models that assume linear elastic deformation of the Earth's crust are routinely used to invert the observed ground motions. The source(s) of deformation in such models are generally interpreted in terms of magma bodies or pathways, and thus form a basis for hazard assessment and mitigation. Using discontinuum mechanics models, we show how host-rock fracturing (i.e. non-elastic deformation) during drainage of a magma body can progressively change the shape and depth of an elastic-deformation source. We argue that this effect explains the marked spatio-temporal changes in source model attributes inferred for the March-April 2007 eruption of Piton de la Fournaise volcano, La Reunion. We find that pronounced deflation-related host-rock fracturing can: (1) yield inclined source model geometries for a horizontal magma body; (2) cause significant upward migration of an elastic-deformation source, leading to underestimation of the true magma body depth and potentially to a misinterpretation of ascending magma; and (3) at least partly explain underestimation by elastic-deformation sources of changes in sub-surface magma volume.

  13. Rock deformation in hydrothermal systems: the nature of fractures in plutons and their host rocks. Technical progress report

    Energy Technology Data Exchange (ETDEWEB)

    Norton, D.

    1981-11-01

    The purpose of this program is to accumulate the types of field data which are important for the analysis of magma-hydrothermal systems. The structural effects of thermal processes were identified in order to distinguish the thermally induced deformations from the deformations that occurred subsequent to complete cooling of the system. Mapping techniques were developed to record the structural data on the ground from local domains characteristic of larger areas in the magma chamber, and in the air from low-angle oblique aerial photography of the entire region. The ground system is complete and preliminary testing is currently being carried out to verify the method. The results indicate that granitic crystalline rocks have no structural resistance to thermal perturbations. If nuclear wastes are to be stored in granite, precautionary buffers would have to be incorporated into the system. A total of 30 fossil magma chambers have been studied over the past 2 years. An extensive set of fracture imagery has been collected, together with information related to the geological history of the plutons. Fossil magma chambers in Arizona, Utah, California, Washington, Montana, and British Columbia have been studied.

  14. Contamination in fractured-rock aquifers: Research at the former Naval Air Warfare Center, West Trenton, New Jersey

    Science.gov (United States)

    Goode, Daniel J.; Tiedeman, Claire; Lacombe, Pierre J.; Imbrigiotta, Thomas E.; Shapiro, Allen M.; Chapelle, Francis H.

    2007-01-01

    The U.S. Geological Survey and cooperators are studying chlorinated solvents in a fractured sedimentary rock aquifer underlying the former Naval Air Warfare Center (NAWC), West Trenton, New Jersey. Fractured-rock aquifers are common in many parts of the United States and are highly susceptible to contamination, particularly at industrial sites. Compared to 'unconsolidated' aquifers, there can be much more uncertainty about the direction and rate of contaminant migration and about the processes and factors that control chemical and microbial transformations of contaminants. Research at the NAWC is improving understanding of the transport and fate of chlorinated solvents in fractured-rock aquifers and will compare the effectiveness of different strategies for contaminant remediation.

  15. Mechanisms of recharge in a fractured porous rock aquifer in a semi-arid region

    Science.gov (United States)

    Manna, Ferdinando; Walton, Kenneth M.; Cherry, John A.; Parker, Beth L.

    2017-12-01

    Eleven porewater profiles in rock core from an upland exposed sandstone vadose zone in southern California, with thickness varying between 10 and 62 m, were analyzed for chloride (Cl) concentration to examine recharge mechanisms, estimate travel times in the vadose zone, assess spatial and temporal variability of recharge, and determine effects of land use changes on recharge. As a function of their location and the local terrain, the profiles were classified into four groups reflecting the range of site characteristics. Century- to millennium-average recharge varied from 4 to 23 mm y-1, corresponding to different average Cl concentrations in the vadose zone and in groundwater, the contribution of diffuse flow (estimated at 80%) and preferential flow (20%) to the total recharge was quantified. This model of dual porosity recharge was tested by simulating transient Cl transport along a physically based narrow column using a discrete fracture-matrix numerical model. Using a new approach based on partitioning both water and Cl between matrix and fracture flow, porewater was dated and vertical displacement rates estimated to range in the sandstone matrix from 3 to 19 cm y-1. Moreover, the temporal variability of recharge was estimated and, along each profile, past recharge rates calculated based on the sequence of Cl concentrations in the vadose zone. Recharge rates increased at specific times coincident with historical changes in land use. The consistency between the timing of land use modifications and changes in Cl concentration and the match between observed and simulated Cl concentration values in the vadose zone provide confidence in porewater age estimates, travel times, recharge estimates, and reconstruction of recharge histories. This study represents an advancement of the application of the chloride mass balance method to simultaneously determine recharge mechanisms and reconstruct location-specific recharge histories in fractured porous rock aquifers. The

  16. The Effect of Boiling on Seismic Properties of Water-Saturated Fractured Rock

    Science.gov (United States)

    Grab, Melchior; Quintal, Beatriz; Caspari, Eva; Deuber, Claudia; Maurer, Hansruedi; Greenhalgh, Stewart

    2017-11-01

    Seismic campaigns for exploring geothermal systems aim at detecting permeable formations in the subsurface and evaluating the energy state of the pore fluids. High-enthalpy geothermal resources are known to contain fluids ranging from liquid water up to liquid-vapor mixtures in regions where boiling occurs and, ultimately, to vapor-dominated fluids, for instance, if hot parts of the reservoir get depressurized during production. In this study, we implement the properties of single- and two-phase fluids into a numerical poroelastic model to compute frequency-dependent seismic velocities and attenuation factors of a fractured rock as a function of fluid state. Fluid properties are computed while considering that thermodynamic interaction between the fluid phases takes place. This leads to frequency-dependent fluid properties and fluid internal attenuation. As shown in a first example, if the fluid contains very small amounts of vapor, fluid internal attenuation is of similar magnitude as attenuation in fractured rock due to other mechanisms. In a second example, seismic properties of a fractured geothermal reservoir with spatially varying fluid properties are calculated. Using the resulting seismic properties as an input model, the seismic response of the reservoir is then computed while the hydrothermal structure is assumed to vary over time. The resulting seismograms demonstrate that anomalies in the seismic response due to fluid state variability are small compared to variations caused by geological background heterogeneity. However, the hydrothermal structure in the reservoir can be delineated from amplitude anomalies when the variations due to geology can be ruled out such as in time-lapse experiments.

  17. Numerical probabilistic analysis for slope stability in fractured rock masses using DFN-DEM approach

    Directory of Open Access Journals (Sweden)

    Alireza Baghbanan

    2017-06-01

    Full Text Available Due to existence of uncertainties in input geometrical properties of fractures, there is not any unique solution for assessing the stability of slopes in jointed rock masses. Therefore, the necessity of applying probabilistic analysis in these cases is inevitable. In this study a probabilistic analysis procedure together with relevant algorithms are developed using Discrete Fracture Network-Distinct Element Method (DFN-DEM approach. In the right abutment of Karun 4 dam and downstream of the dam body, five joint sets and one major joint have been identified. According to the geometrical properties of fractures in Karun river valley, instability situations are probable in this abutment. In order to evaluate the stability of the rock slope, different combinations of joint set geometrical parameters are selected, and a series of numerical DEM simulations are performed on generated and validated DFN models in DFN-DEM approach to measure minimum required support patterns in dry and saturated conditions. Results indicate that the distribution of required bolt length is well fitted with a lognormal distribution in both circumstances. In dry conditions, the calculated mean value is 1125.3 m, and more than 80 percent of models need only 1614.99 m of bolts which is a bolt pattern with 2 m spacing and 12 m length. However, as for the slopes with saturated condition, the calculated mean value is 1821.8 m, and more than 80 percent of models need only 2653.49 m of bolts which is equivalent to a bolt pattern with 15 m length and 1.5 m spacing. Comparison between obtained results with numerical and empirical method show that investigation of a slope stability with different DFN realizations which conducted in different block patterns is more efficient than the empirical methods.

  18. Continuum-based DFN-consistent simulations of oxygen ingress in fractured crystalline rocks

    Science.gov (United States)

    Trinchero, P.; Puigdomenech, I.; Molinero, J.; Ebrahimi, H.; Gylling, B.; Svensson, U.; Bosbach, D.; Deissmann, G.

    2016-12-01

    The potential transient infiltration of oxygenated glacial meltwater into initially anoxic and reducing fractured crystalline rocks during glaciation events is an issue of concern for some of the prospected deep geological repositories for spent nuclear fuel. Here, this problem is assessed using reactive transport calculations. First, a novel parameterisation procedure is presented, where flow, transport and geochemical parameters (i.e. hydraulic conductivity, effective/kinetic porosity, and mineral specific surface and abundance) are defined on a finite volume numerical grid based on the (spatially varying) properties of an underlying Discrete Fracture Network (DFN). Second, using this approach, a realistic reactive transport model of Forsmark, i.e. the selected site for the proposed Swedish spent nuclear fuel repository, is implemented. The model consists of more than 70 million geochemical transport degrees of freedom and simulates the ingress of oxygen-rich water from the recharge area of the domain and its depletion due to reactions with the Fe(II) mineral chlorite. Third, the calculations are solved in the supercomputer JUQUEEN of the Jülich Supercomputing Centre. The results of the simulations show that oxygen infiltrates relatively quickly along fractures and deformation zones until a steady state profile is reached, where geochemical reactions counterbalance advective transport processes. Interestingly, most of the iron-bearing minerals are consumed in the highly conductive zones, where larger mineral surfaces are available for reactions. An analysis based on mineral mass balance shows that the considered rock medium has enough capacity to buffer oxygen infiltration for a long period of time (i.e. some thousand years).

  19. HRL Aespoe - two-phase flow experiment - gas and water flow in fractured crystalline rock

    International Nuclear Information System (INIS)

    Kull, H.; Liedtke, L.

    1998-01-01

    (The full text of the contribution follows:) Gas generated from radioactive waste may influence the hydraulic and mechanical properties of the man-made barriers and the immediate surroundings of the repository. Prediction of alteration in fractured crystalline rock is difficult. There is a lack of experimental data, and calibrated models are not yet available. Because of the general importance of this matter the German Federal Ministry for Education, Science, Research and Technology decided to conduct a two-phase flow study at HRL Aespoe within the scope of the co-operation agreement with SKB. Within the presentation an overview of field experiments and modelling studies scheduled until end of '99 are given. Conceptual models for one- and two-phase flow, methodologies and with respect to numerical calculations necessary parameter set-ups are discussed. Common objective of in-situ experiments is to calibrate flow models to improve the reliability of predictions for gas migration through fractured rock mass. Hence, in a defined dipole flow field in niche 2/715 at HRL Aespoe effective hydraulic parameters are evaluated. Numerical modelling of non-isothermal, two-phase, two-component processes is feasible only for two-dimensional representation of a porous medium. To overcome this restriction a computer program will be developed to model three-dimensional, fractured, porous media. Rational aspects of two-phase flow studies are for the designing of geotechnical barriers and for the long-term safety analysis of potential radionuclide transport in a future repository required for the licensing process

  20. Steady-state flow in a rock mass intersected by permeable fracture zones

    International Nuclear Information System (INIS)

    Lindbom, B.

    1986-12-01

    Level 1 of HYDROCOIN consists of seven well-defined test problems. This paper is concerned with Case 2, which is formulated as a generic groundwater flow situation often found in crystalline rock with highly permeable fracture zones in a less permeable rock mass. The case is two-dimensional and modelled with 8-noded, isoparametric, rectangular elements. According to the case definition, calculations of hydraulic head and particle tracking are performed. The computations are carried out with varying degree of discretisation in order to analyse possible impact on the result with respect to nodal density. Further calculations have been performed mainly devoted to mass balance deviations and how these are affected by permeability contrasts, varying degree of spatial discretisation and distortion of finite elements. The distribution of hydraulic head in the domain is less sensitive to differences in nodal density than the trajectories. The hydraulic heads show similar behaviour for three meshes with varying degrees of discretisation. The particle tracking seems to be more sensitive to the level of discretisation. The results obtained with a coarse and medium mesh indicate completely different solutions for one of the pathlines. The coarse mesh is too sparsely discretised for the specified problem. The local mass balance is evaluated for seven runs. The mass balance deviation seems to be considerably more sensitive to the level of discretisation than to both permeability contrasts and deformation of elements. The permeability contrasts between the rock mass and fracture zones vary from a factor of 1000 to 1 (homogeneous properties) with increments of a factor of 10. These calculations in fact give better mass balance with increasing permeability contrasts, contrary to what could be expected. (orig./HP)

  1. Geomass: geological modelling analysis and simulation software for the characterisation of fractured hard rock environments

    International Nuclear Information System (INIS)

    White, M.J.; Humm, J.P.; Todaka, N.; Takeuchi, S.

    1998-01-01

    This paper presents the development and functionality of a suite of applications which are being developed to support the geological investigations in the Tono URL. GEOMASS will include 3D geological modelling, 3D fluid flow and solute transport and 3D visualisation capabilities. The 3D geological modelling in GEOMASS will be undertaken using a commercially available 3D geological modelling system, EarthVision. EarthVision provides 3D mapping, interpolation, analysis and well planning software. It is being used in the GEOMASS system to provide the geological framework (structure of the tectonic faults and stratigraphic and lithological contacts) to the 3D flow code. It is also being used to gather the geological data into a standard format for use throughout the investigation programme. The 3D flow solver to be used in GEOMASS is called Frac-Affinity. Frac-Affinity models the 3D geometry of the flow system as a hybrid medium, in which the rock contains both permeable, intact rock and fractures. Frac-Affinity also performs interpolation of heterogeneous rock mass property data using a fractal based approach and the generation of stochastic fracture networks. The code solves for transient flow over a user defined sub-region of the geological framework supplied by EarthVision. The results from Frac-Affinity are passed back to EarthVision so that the flow simulation can be visualized alongside the geological structure. This work-flow allows rapid assessment of the role of geological features in controlling flow. This paper will present the concepts and approach of GEOMASS and illustrate the practical application of GEOMASS using data from Tono

  2. Colloid and radionuclide retention mechanisms in fractured rock under near-natural flow conditions

    International Nuclear Information System (INIS)

    Delos, A.; Schaefer, T.; Geckeis, H.; Guimera, J.; Carrera, J.; Fanghaenel, T.

    2005-01-01

    Full text of publication follows: Experiments in fractured host rock (Grimsel Test Site, GTS, Switzerland) revealed that the colloid relevance for actinide migration is high due to the specific geochemical groundwater conditions [1]. However, even under such conditions it is found that retention of colloids and colloid-borne actinides becomes significant under near-natural groundwater flow rates (1-10 m/a) [2]. Underlying mechanisms of colloid and radionuclide retention are not well understood up to now. The present study co-funded by the NoE ACTINET-6 focuses on (i) the kinetics of actinide-colloid interactions and (ii) the relevance of matrix diffusion as a competition process to other retention mechanisms which affect the actinides behavior in fractured rock systems such as the Grimsel granodiorite. Colloid migration is studied with well defined model colloids as e.g. fluorescence dyed carboxylated polystyrene particles, and natural colloids extracted from bentonite (FEBEX) and from fracture filling material (GTS). In order to study the influence of matrix porosity on actinides migration, those experiments are performed in columns of well defined geometry filled with microporous unmodified silica spheres, porous ceramic material and natural fracture filling material from the GTS. The behaviour of actinides (Pu(IV) and Am(III)) sorbed onto bentonite colloids is investigated in column and batch experiments. All experiments are performed under anoxic conditions. Colloid characterization methods used in this study include the combination of photon correlation spectroscopy (PCS), laser-induced breakdown detection (LIBD), fluorimetry and field flow fractionation (FFF). Experimental results and their application to the parametrisation of reactive colloid transport models are discussed. [1] Geckeis H, Schaefer T, Hauser W, Rabung T, Missana T, Degueldre C, Moeri A, Eikenberg J, Fierz T, Alexander WR (2004) Results of the Colloid and Radionuclide Retention experiment

  3. Investigated conductive fracture in the granitic rocks by flow-meter logging

    International Nuclear Information System (INIS)

    Ogata, Nobuhisa; Koide, Kaoru; Takeichi, Atsushi

    1997-01-01

    Test of the use of a measurement technique for the hydraulic conductivity of geological structures which act as flow paths or are impermeable to groundwater flow. In order to prove the value of flow-meter logging as an in-situ technique for detecting conductive fractures in granitic rocks, the method has been applied to a borehole near the Tono uranium mine, Gifu, Japan. This study in involved with detecting a conductive fracture and calculating the hydraulic conductivities. The results were as follows: (1) In a zone of groundwater inflow into the borehole, the hydraulic conductivity was calculated to be of the order of the 10 -3 - 10 -4 (cm/sec) from flow-meter logging. This value agreed with the results of a in-situ borehole permeability test carried out with a similar depth interval. (2) The study showed that flow-meter logging is effective for detecting the distribution of high conductivity fractures and calculating the hydraulic conductivity. (author)

  4. Fracture detection in crystalline rock using ultrasonic reflection techniques: Volume 1

    International Nuclear Information System (INIS)

    Palmer, S.P.

    1982-11-01

    This research was initiated to investigate using ultrasonic seismic reflection techniques to detect fracture discontinuities in a granitic rock. Initial compressional (P) and shear (SH) wave experiments were performed on a 0.9 x 0.9 x 0.3 meter granite slab in an attempt to detect seismic energy reflected from the opposite face of the slab. It was found that processing techniques such as deconvolution and array synthesis could improve the standout of the reflection event. During the summers of 1979 and 1980 SH reflection experiments were performed at a granite quarry near Knowles, California. The purpose of this study was to use SH reflection methods to detect an in situ fracture located one to three meters behind the quarry face. These SH data were later analyzed using methods similar to those applied in the laboratory. Interpretation of the later-arriving events observed in the SH field data as reflections from a steeply-dipping fracture was inconclusive. 41 refs., 43 figs., 7 tabs

  5. Summary report on the up-scaling of the retention properties by matrix diffusion in fractured rock

    International Nuclear Information System (INIS)

    Poteri, A.

    2009-02-01

    Fractured rocks are composed of porous but almost impermeable rock matrix and water conducting fractures. The main characteristic of the fractured rock is the great heterogeneity in different scales that leads to preferential flow paths and channelling of the flow. Three distinct flow environments can be identified: channeling that causes variable flow in the individual fracture planes, transmissivity differences between fractures that leads to preferential flow paths and extensive fracture zones that provide highly transmissive connections over long distances. Large and transmissive fractures have an important role to the flow and transport properties of the fractured rock. Flow paths tend to accumulate on the large features that carry the majority of the flow. Modelling exercises have indicated persistence of the flow properties along the flow paths. This means that once a particle has entered a major flow path it tends to follow the high flow rate channel. The main challenge in spatial up-scaling of the retention properties is connected to the description of the flow characteristics in the fractured rock. The importance of individual fractures to the overall retention is proportional to the flow rate along the fracture. This means that simulations need to consider individual fractures. Fracture network modelling offers a suitable approach that is able to take into account the multiscale structure of the fractured rock and to determine retention properties of the flow paths. It also provides a straightforward way to up-scale transport properties along the preferential flow paths through the fracture network. However, the computational feasibility of the site scale applications in the performance assessment limits the range of different size fractures that can be taken into account in the fracture network simulations. Heterogeneity in the immobile zone properties may influence effective retention properties if the heterogeneity is coupled with a limited capacity

  6. Repository site data report for unsaturated tuff, Yucca Mountain, Nevada

    International Nuclear Information System (INIS)

    Tien, P.L.; Updegraff, C.D.; Siegel, M.D.; Wahi, K.K.; Guzowski, R.V.

    1985-11-01

    The US Department of Energy is currently considering the thick sequences of unsaturated, fractured tuff at Yucca Mountain, on the southwestern boundary of the Nevada Test Site, as a possible candidate host rock for a nuclear-waste repository. Yucca Mountain is in one of the most arid areas in the United States. The site is within the south-central part of the Great Basin section of the Basin and Range physiographic province and is located near a number of silicic calderas of Tertiary age. Although localized zones of seismic activity are common throughout the province, and faults are present at Yucca Mountain, the site itself is basically aseismic. No data are available on the composition of ground water in the unsaturated zone at Yucca Mountain. It has been suggested that the composition is bounded by the compositions of water from wells USW-H3, UE25p-1, J-13, and snow or rain. There are relatively few data available from Yucca Mountain on the moisture content and saturation, hydraulic conductivity, and characteristic curves of the unsaturated zone. The available literature on thermomechanical properties of tuff does not always distinguish between data from the saturated zone and data from the unsaturated zone. Geochemical, hydrologic, and thermomechanical data available on the unsaturated tuffs of Yucca Mountain are tabulated in this report. Where the data are very sparse, they have been supplemented by data from the saturated zone or from areas other than Yucca Mountain. 316 refs., 58 figs., 37 tabs

  7. Repository site data report for unsaturated tuff, Yucca Mountain, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Tien, P.L.; Updegraff, C.D.; Siegel, M.D.; Wahi, K.K.; Guzowski, R.V.

    1985-11-01

    The US Department of Energy is currently considering the thick sequences of unsaturated, fractured tuff at Yucca Mountain, on the southwestern boundary of the Nevada Test Site, as a possible candidate host rock for a nuclear-waste repository. Yucca Mountain is in one of the most arid areas in the United States. The site is within the south-central part of the Great Basin section of the Basin and Range physiographic province and is located near a number of silicic calderas of Tertiary age. Although localized zones of seismic activity are common throughout the province, and faults are present at Yucca Mountain, the site itself is basically aseismic. No data are available on the composition of ground water in the unsaturated zone at Yucca Mountain. It has been suggested that the composition is bounded by the compositions of water from wells USW-H3, UE25p-1, J-13, and snow or rain. There are relatively few data available from Yucca Mountain on the moisture content and saturation, hydraulic conductivity, and characteristic curves of the unsaturated zone. The available literature on thermomechanical properties of tuff does not always distinguish between data from the saturated zone and data from the unsaturated zone. Geochemical, hydrologic, and thermomechanical data available on the unsaturated tuffs of Yucca Mountain are tabulated in this report. Where the data are very sparse, they have been supplemented by data from the saturated zone or from areas other than Yucca Mountain. 316 refs., 58 figs., 37 tabs.

  8. Aespoe Hard Rock Laboratory. Analysis of fracture networks based on the integration of structural and hydrogeological observations on different scales

    Energy Technology Data Exchange (ETDEWEB)

    Bossart, P. [Geotechnical Inst. Ltd., Bern (Switzerland); Hermanson, Jan [Golder Associates, Stockholm (Sweden); Mazurek, M. [Univ. of Bern (Switzerland)

    2001-05-01

    Fracture networks at Aespoe have been studied for several rock types exhibiting different degrees of ductile and brittle deformation, as well as on different scales. Mesoscopic fault systems have been characterised and classified in an earlier report, this report focuses mainly on fracture networks derived on smaller scales, but also includes mesoscopic and larger scales. The TRUE-1 block has been selected for detailed structural analysis on a small scale due to the high density of relevant information. In addition to the data obtained from core materials, structural maps, BIP data and the results of hydro tests were synthesised to derive a conceptual structural model. The approach used to derive this conceptual model is based on the integration of deterministic structural evidence, probabilistic information and both upscaling and downscaling of observations and concepts derived on different scales. Twelve fracture networks mapped at different sites and scales and exhibiting various styles of tectonic deformation were analysed for fractal properties and structural and hydraulic interconnectedness. It was shown that these analysed fracture networks are not self-similar. An important result is the structural and hydraulic interconnectedness of fracture networks on all scales in the Aespoe rocks, which is further corroborated by geochemical evidence. Due to the structural and hydraulic interconnectedness of fracture systems on all scales at Aespoe, contaminants from waste canisters placed in tectonically low deformation environments would be transported - after having passed through the engineered barriers -from low-permeability fractures towards higher permeability fractures and may thus eventually reach high-permeability features.

  9. Aespoe Hard Rock Laboratory. Analysis of fracture networks based on the integration of structural and hydrogeological observations on different scales

    International Nuclear Information System (INIS)

    Bossart, P.; Hermanson, Jan; Mazurek, M.

    2001-05-01

    Fracture networks at Aespoe have been studied for several rock types exhibiting different degrees of ductile and brittle deformation, as well as on different scales. Mesoscopic fault systems have been characterised and classified in an earlier report, this report focuses mainly on fracture networks derived on smaller scales, but also includes mesoscopic and larger scales. The TRUE-1 block has been selected for detailed structural analysis on a small scale due to the high density of relevant information. In addition to the data obtained from core materials, structural maps, BIP data and the results of hydro tests were synthesised to derive a conceptual structural model. The approach used to derive this conceptual model is based on the integration of deterministic structural evidence, probabilistic information and both upscaling and downscaling of observations and concepts derived on different scales. Twelve fracture networks mapped at different sites and scales and exhibiting various styles of tectonic deformation were analysed for fractal properties and structural and hydraulic interconnectedness. It was shown that these analysed fracture networks are not self-similar. An important result is the structural and hydraulic interconnectedness of fracture networks on all scales in the Aespoe rocks, which is further corroborated by geochemical evidence. Due to the structural and hydraulic interconnectedness of fracture systems on all scales at Aespoe, contaminants from waste canisters placed in tectonically low deformation environments would be transported - after having passed through the engineered barriers -from low-permeability fractures towards higher permeability fractures and may thus eventually reach high-permeability features

  10. Experimental and numerical study on the fracture of rocks during injection of CO2-saturated water

    Science.gov (United States)

    Li, Qi; Wu, Zhishen; Lei, Xing-Lin; Murakami, Yutaka; Satoh, Takashi

    2007-02-01

    Geological sequestration of CO2 into depleted hydrocarbon reserviors or saline aquifers presents the enormous potential to reduce greenhouse gas emission from fossil fuels. However, it may give rise to a complicated coupling physical and chemical process. One of the processes is the hydro-mechanical impact of CO2 injection. During the injection project, the increase of pore pressures of storing formations can induce the instability, which finally results in a catastrophic failure of disposal sites. This paper focuses mainly on the role of CO2-saturated water in the fracturing behavior of rocks. To investigate how much the dissolved CO2 can influence the pore pressure change of rocks, acoustic emission (AE) experiments were performed on sandstone and granite samples under triaxial conditions. The main innovation of this paper is to propose a time dependent porosity method to simulate the abrupt failure process, which is observed in the laboratory and induced by the pore pressure change due to the volume dilatancy of rocks, using a finite element scheme associated with two-phase characteristics. The results successfully explained the phenomena obtained in the physical experiments.

  11. Mathematical algorithm development and parametric studies with the GEOFRAC three-dimensional stochastic model of natural rock fracture systems

    Science.gov (United States)

    Ivanova, Violeta M.; Sousa, Rita; Murrihy, Brian; Einstein, Herbert H.

    2014-06-01

    This paper presents results from research conducted at MIT during 2010-2012 on modeling of natural rock fracture systems with the GEOFRAC three-dimensional stochastic model. Following a background summary of discrete fracture network models and a brief introduction of GEOFRAC, the paper provides a thorough description of the newly developed mathematical and computer algorithms for fracture intensity, aperture, and intersection representation, which have been implemented in MATLAB. The new methods optimize, in particular, the representation of fracture intensity in terms of cumulative fracture area per unit volume, P32, via the Poisson-Voronoi Tessellation of planes into polygonal fracture shapes. In addition, fracture apertures now can be represented probabilistically or deterministically whereas the newly implemented intersection algorithms allow for computing discrete pathways of interconnected fractures. In conclusion, results from a statistical parametric study, which was conducted with the enhanced GEOFRAC model and the new MATLAB-based Monte Carlo simulation program FRACSIM, demonstrate how fracture intensity, size, and orientations influence fracture connectivity.

  12. Rock fragmentation

    Energy Technology Data Exchange (ETDEWEB)

    Brown, W.S.; Green, S.J.; Hakala, W.W.; Hustrulid, W.A.; Maurer, W.C. (eds.)

    1976-01-01

    Experts in rock mechanics, mining, excavation, drilling, tunneling and use of underground space met to discuss the relative merits of a wide variety of rock fragmentation schemes. Information is presented on novel rock fracturing techniques; tunneling using electron beams, thermocorer, electric spark drills, water jets, and diamond drills; and rock fracturing research needs for mining and underground construction. (LCL)

  13. A gas migration test in saturated, fractured rock. Final report for the Joint UKDOE/AECL Project. Phase 2

    Energy Technology Data Exchange (ETDEWEB)

    Gascoyne, M.; Wuschke, D.M.; Brown, A.; Hayles, J.G.; Kozak, E.T.; Lodha, G.S.; Thorne, G.A. [Atomic Energy of Canada Ltd., Pinawa, MB (Canada). Whiteshell Labs.

    1991-12-31

    Helium gas was injected at constant pressure into an inclined fracture zone through an access borehole at a depth of about 40 m, in the Lac du Bonnet granite, southeastern Manitoba. The gas flow rate, arrival time and pattern of distribution of gas at the surface were monitored by soil gas surveys. The field results were compared with predictions of a simple analytical model. Good agreement was found when the influence of vertical fracturing in the bedrock and a low-permeability overburden were included in the model. The model was then used to determine the hydraulic conductivity of individual gas flow paths in the fractured rock. (author).

  14. A gas migration test in saturated, fractured rock. Final report for the Joint UKDOE/AECL Project. Phase 2

    Energy Technology Data Exchange (ETDEWEB)

    Gascoyne, M; Wuschke, D M; Brown, A; Hayles, J G; Kozak, E T; Lodha, G S; Thorne, G A [Atomic Energy of Canada Ltd., Pinawa, MB (Canada). Whiteshell Labs.

    1992-12-31

    Helium gas was injected at constant pressure into an inclined fracture zone through an access borehole at a depth of about 40 m, in the Lac du Bonnet granite, southeastern Manitoba. The gas flow rate, arrival time and pattern of distribution of gas at the surface were monitored by soil gas surveys. The field results were compared with predictions of a simple analytical model. Good agreement was found when the influence of vertical fracturing in the bedrock and a low-permeability overburden were included in the model. The model was then used to determine the hydraulic conductivity of individual gas flow paths in the fractured rock. (author).

  15. Influence of scale-dependent fracture intensity on block size distribution and rock slope failure mechanisms in a DFN framework

    Science.gov (United States)

    Agliardi, Federico; Galletti, Laura; Riva, Federico; Zanchi, Andrea; Crosta, Giovanni B.

    2017-04-01

    An accurate characterization of the geometry and intensity of discontinuities in a rock mass is key to assess block size distribution and degree of freedom. These are the main controls on the magnitude and mechanisms of rock slope instabilities (structurally-controlled, step-path or mass failures) and rock mass strength and deformability. Nevertheless, the use of over-simplified discontinuity characterization approaches, unable to capture the stochastic nature of discontinuity features, often hampers a correct identification of dominant rock mass behaviour. Discrete Fracture Network (DFN) modelling tools have provided new opportunities to overcome these caveats. Nevertheless, their ability to provide a representative picture of reality strongly depends on the quality and scale of field data collection. Here we used DFN modelling with FracmanTM to investigate the influence of fracture intensity, characterized on different scales and with different techniques, on the geometry and size distribution of generated blocks, in a rock slope stability perspective. We focused on a test site near Lecco (Southern Alps, Italy), where 600 m high cliffs in thickly-bedded limestones folded at the slope scale impend on the Lake Como. We characterized the 3D slope geometry by Structure-from-Motion photogrammetry (range: 150-1500m; point cloud density > 50 pts/m2). Since the nature and attributes of discontinuities are controlled by brittle failure processes associated to large-scale folding, we performed a field characterization of meso-structural features (faults and related kinematics, vein and joint associations) in different fold domains. We characterized the discontinuity populations identified by structural geology on different spatial scales ranging from outcrops (field surveys and photo-mapping) to large slope sectors (point cloud and photo-mapping). For each sampling domain, we characterized discontinuity orientation statistics and performed fracture mapping and circular

  16. A study on the stochastic model for nuclide transport in the fractured porous rock using continuous time Markov process

    International Nuclear Information System (INIS)

    Lee, Youn Myoung

    1995-02-01

    As a newly approaching model, a stochastic model using continuous time Markov process for nuclide decay chain transport of arbitrary length in the fractured porous rock medium has been proposed, by which the need for solving a set of partial differential equations corresponding to various sets of side conditions can be avoided. Once the single planar fracture in the rock matrix is represented by a series of finite number of compartments having region wise constant parameter values in them, the medium is continuous in view of various processes associated with nuclide transport but discrete in medium space and such geologic system is assumed to have Markov property, since the Markov process requires that only the present value of the time dependent random variable be known to determine the future value of random variable, nuclide transport in the medium can then be modeled as a continuous time Markov process. Processes that are involved in nuclide transport are advective transport due to groundwater flow, diffusion into the rock matrix, adsorption onto the wall of the fracture and within the pores in the rock matrix, and radioactive decay chain. The transition probabilities for nuclide from the transition intensities between and out of the compartments are represented utilizing Chapman-Kolmogorov equation, through which the expectation and the variance of nuclide distribution for each compartment or the fractured rock medium can be obtained. Some comparisons between Markov process model developed in this work and available analytical solutions for one-dimensional layered porous medium, fractured medium with rock matrix diffusion, and porous medium considering three member nuclide decay chain without rock matrix diffusion have been made showing comparatively good agreement for all cases. To verify the model developed in this work another comparative study was also made by fitting the experimental data obtained with NaLS and uranine running in the artificial fractured

  17. Field assessment of the use of borehole pressure transients to measure the permeability of fractured rock masses

    International Nuclear Information System (INIS)

    Forster, C.B.; Gale, J.E.

    1981-06-01

    A field experiment to evaluate the transient pressure pulse technique as a method of determining the in-situ hydraulic conductivity of low permeability fractured rock was made. The experiment attempted to define: the radius of influence of a pressure pulse-test in fractured rock and the correlation between pressure-pulse tests and steady-state flow tests performed in five boreholes drilled in fractured granite. Twenty-five test intervals, 2 to 3 m in length, were isolated in the boreholes, using air-inflated packers. During pressure pulse and steady-state tests, pressures were monitored in both the test and observation cavities. Rock-mass conductivities were calculated from steady-state test results and were found to range from less than 10 - 11 to 10 - 7 cm/sec. However, there was no consistent correlation between the steady-state conductivity and the pressure pulse decay characteristics of individual intervals. These conflicting test results can be attributed to the following factors: differences in volumes of rock affected by the test techniques; effects of equipment configuration and compliance; and complexity of the fracture network. Although the steady-state flow tests indicate that hydraulic connections exist between most of the test cavities, no pressure responses were noted in the observation cavities (located at least 0.3 m from the test cavities) during the pulse tests. This does not mean, however, that the pressure-pulse radius of influence is <0.3 m, because the observation cavities were too large (about 7 liters). The lack of correlation between steady-state conductivities and the corresponding pressure pulse decay times does not permit use of existing single-fracture type curves to analyze pulse tests performed in multiple-fracture intervals. Subsequent work should focus on the detailed interpretation of field results with particular reference to the effects of the fracture system at the test site

  18. Near Wellbore Hydraulic Fracture Propagation from Perforations in Tight Rocks: The Roles of Fracturing Fluid Viscosity and Injection Rate

    Directory of Open Access Journals (Sweden)

    Seyed Hassan Fallahzadeh

    2017-03-01

    Full Text Available Hydraulic fracture initiation and near wellbore propagation is governed by complex failure mechanisms, especially in cased perforated wellbores. Various parameters affect such mechanisms, including fracturing fluid viscosity and injection rate. In this study, three different fracturing fluids with viscosities ranging from 20 to 600 Pa.s were used to investigate the effects of varying fracturing fluid viscosities and fluid injection rates on the fracturing mechanisms. Hydraulic fracturing tests were conducted in cased perforated boreholes made in tight 150 mm synthetic cubic samples. A true tri-axial stress cell was used to simulate real far field stress conditions. In addition, dimensional analyses were performed to correspond the results of lab experiments to field-scale operations. The results indicated that by increasing the fracturing fluid viscosity and injection rate, the fracturing energy increased, and consequently, higher fracturing pressures were observed. However, when the fracturing energy was transferred to a borehole at a faster rate, the fracture initiation angle also increased. This resulted in more curved fracture planes. Accordingly, a new parameter, called fracturing power, was introduced to relate fracture geometry to fluid viscosity and injection rate. Furthermore, it was observed that the presence of casing in the wellbore impacted the stress distribution around the casing in such a way that the fracture propagation deviated from the wellbore vicinity.

  19. Analysis of constant-head well tests in nonporous fractured rock

    International Nuclear Information System (INIS)

    Doe, T.; Remer, J.

    1981-01-01

    If one compares the results of steady analyses and transient flowrate analyses, the error in assuming steady flow is less than an order of magnitude for reasonable values of storativity, and this error can be minimized through proper choice of radius of influence. Although the steady flow assumptions do not result in large errors in the calculation of permeability, careful design of constant-head well tests can yield not only storativity, but also qualitative information on the areal extent of permeable zones or fractures tested. Constant-head well tests have several major advantages over other well test techniques in low permeability rock. Unlike pump tests, wellbore storage effects are virtually nonexistant. Provided low-flow measurement apparatus is available, constant-level tests are far more rapid than slug tests and, unlike pulse tests, compliance of equipment is not a factor, since the system is maintained at constant pressure throughout the test

  20. Hydrogeloogic characterization of fractured rock formations: A guide for groundwater remediators

    International Nuclear Information System (INIS)

    Cohen, A.J.B.

    1995-10-01

    A field site was developed in the foothills of the Sierra Nevada, California to develop and test a multi-disciplinary approach to the characterization of ground water flow and transport in fractured rocks. Nine boreholes were drilled into the granitic bedrock, and a wide variety of new and traditional subsurface characterization tools were implemented. The hydrogeologic structure and properties of the field site were deduced by integrating results from the various geologic, geophysical, hydrologic, and other investigative methods. The findings of this work are synthesized into this report, which is structured in a guidebook format. The applications of the new and traditional technologies, suggestions on how best to use, integrate, and analyze field data, and comparisons of the shortcoming and benefits of the different methods are presented

  1. Hydrogeloogic characterization of fractured rock formations: A guide for groundwater remediators

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, A.J.B.

    1995-10-01

    A field site was developed in the foothills of the Sierra Nevada, California to develop and test a multi-disciplinary approach to the characterization of ground water flow and transport in fractured rocks. Nine boreholes were drilled into the granitic bedrock, and a wide variety of new and traditional subsurface characterization tools were implemented. The hydrogeologic structure and properties of the field site were deduced by integrating results from the various geologic, geophysical, hydrologic, and other investigative methods. The findings of this work are synthesized into this report, which is structured in a guidebook format. The applications of the new and traditional technologies, suggestions on how best to use, integrate, and analyze field data, and comparisons of the shortcoming and benefits of the different methods are presented.

  2. Rock-water interaction involving uranium and thorium isotopes in the fractures of El Berrocal granite, Spain

    International Nuclear Information System (INIS)

    Ivanovich, M.; Cahmbers, N.; Hernandez-Benitez, A.

    1996-01-01

    In the framework of a number of R and D programmes, low permeability rocks in which the groundwater flow is governed by fractures are being considered as potentially suitable candidates for the long-term storage of radioactive waste at depth [1]. Such rocks are often one of the main sources of the radionuclides deriving from the natural radioactive decay chains headed by U and Th. This characteristic makes this type of rock very useful in providing geochemical analogues for the behaviour of transuranic radionuclides present in the nuclear waste [2,3]. The main aim of the work reported here is to study in detail the distribution of naturally occurring radionuclides in several types of fracture infill material from the El Berrocal granitic pluton. The pluton in situated at the southern edge of the Spanish Central System and contains a uranium-mineralized quartz vein (UQV) that has been mined for uranium in the past [4]. Groundwaters as well as natural colloids have been sampled from some of the boreholes with the ultimate intention to model rock/water interaction processes which may take place in the water-bearing fractures in the batholith. The second aim of this work has been to date some of the calcite-rich fracture infills derived from the drill cores at depth, especially at water-bearing horizons. (Author)

  3. A global sensitivity analysis of two-phase flow between fractured crystalline rock and bentonite with application to spent nuclear fuel disposal.

    Science.gov (United States)

    Dessirier, Benoît; Frampton, Andrew; Jarsjö, Jerker

    2015-11-01

    Geological disposal of spent nuclear fuel in deep crystalline rock is investigated as a possible long term solution in Sweden and Finland. The fuel rods would be cased in copper canisters and deposited in vertical holes in the floor of deep underground tunnels, embedded within an engineered bentonite buffer. Recent experiments at the Äspö Hard Rock Laboratory (Sweden) showed that the high suction of unsaturated bentonite causes a de-saturation of the adjacent rock at the time of installation, which was also independently predicted in model experiments. Remaining air can affect the flow patterns and alter bio-geochemical conditions, influencing for instance the transport of radionuclides in the case of canister failure. However, thus far, observations and model realizations are limited in number and do not capture the conceivable range and combination of parameter values and boundary conditions that are relevant for the thousands of deposition holes envisioned in an operational final repository. In order to decrease this knowledge gap, we introduce here a formalized, systematic and fully integrated approach to study the combined impact of multiple factors on air saturation and dissolution predictions, investigating the impact of variability in parameter values, geometry and boundary conditions on bentonite buffer saturation times and on occurrences of rock de-saturation. Results showed that four parameters consistently appear in the top six influential factors for all considered output (target) variables: the position of the fracture intersecting the deposition hole, the background rock permeability, the suction representing the relative humidity in the open tunnel and the far field pressure value. The combined influence of these compared to the other parameters increases as one targets a larger fraction of the buffer reaching near-saturation. Strong interaction effects were found, which means that some parameter combinations yielded results (e.g., time to

  4. Groundwater flow into underground openings in fractured crystalline rocks: an interpretation based on long channels

    Science.gov (United States)

    Black, John H.; Woodman, Nicholas D.; Barker, John A.

    2017-03-01

    Rethinking an old tracer experiment in fractured crystalline rock suggests a concept of groundwater flow in sparse networks of long channels that is supported by results from an innovative lattice network model. The model, HyperConv, can vary the mean length of `strings' of connected bonds, and the gaps between them, using two independent probability functions. It is found that networks of long channels are able to percolate at lower values of (bond) density than networks of short channels. A general relationship between mean channel length, mean gap length and probability of percolation has been developed which incorporates the well-established result for `classical' lattice network models as a special case. Using parameters appropriate to a 4-m diameter drift located 360 m below surface at Stripa Mine Underground Research Laboratory in Sweden, HyperConv is able to reproduce values of apparent positive skin, as observed in the so-called Macropermeability Experiment, but only when mean channel length exceeds 10 m. This implies that such channel systems must cross many fracture intersections without bifurcating. A general relationship in terms of flow dimension is suggested. Some initial investigations using HyperConv show that the commonly observed feature, `compartmentalization', only occurs when channel density is just above the percolation threshold. Such compartments have been observed at Kamaishi Experimental Mine (Japan) implying a sparse flow network. It is suggested that compartments and skin are observable in the field, indicate sparse channel systems, and could form part of site characterization for deep nuclear waste repositories.

  5. Natural analogue studies in crystalline rock: the influence of water-bearing fractures on radionuclide immobilisation in a granitic rock repository

    International Nuclear Information System (INIS)

    Alexander, W.R.; MacKenzie, A.B.; Scott, R.D.; McKinley, I.G.

    1990-06-01

    Current Swiss concepts for the disposal of radioactive waste involve disposal in deep mined repositories to ensure that only insignificant quantities of radionuclides will ever reach the surface and so enter the biosphere. The rock formations presently considered as potential candidates for hosting radwaste repositories have thus been selected on the basis of their capacity to isolate radionuclides from the biosphere. An important factor in ensuring such containment is a very low solute transport rate through the host formation. However, it is considered likely that, in the formations of interest in the Swiss programme (eg. granites, argillaceous sediments, anhydrite), the rocks will be fractured to some extent even at repository depth. In the instance of the cumulative failure of near-field barriers in the repository, these hydraulically connected fractures in the host formation could be very important far-field routes of migration (and possible sites of retardation) of radionuclides dissolved in the groundwaters. In this context, the so-called 'matrix diffusion' mechanism is potentially very important for radionuclide retardation. This report is the culmination of a programme which has attempted to assess the potential influence of these water-bearing fractures on radionuclide transport in a crystalline rock radwaste repository. 162 refs., 36 figs., 16 tabs

  6. Borehole radar applied to the characterization of hydraulically conductive fracture zones in crystalline rock

    International Nuclear Information System (INIS)

    Olsson, O.; Falk, L.; Forslund, O.; Lundmark, L.; Sandberg, E.

    1992-01-01

    This paper discusses the borehole radar system, RAMAC, developed within the framework of the International Stripa Project, which can be used in three different measuring modes; single-hole reflection, cross-hole reflection and cross-hole tomography. The reflection modes basically provide geometrical data on features located at some distance from the borehole. In addition the strength of the reflections indicate the contrast in electrical properties. Single-hole reflection data are cylindrically symmetrical with respect to the borehole, which means that a unique fracture orientation cannot be obtained. A method has been devised where absolute orientation of fracture zones is obtained by combining single-hole reflection data from adjacent holes. Similar methods for the analysis of cross-hole reflection data have also been developed and found to be efficient. The radar operates in the frequency range 20-60 MHz which gives a resolution of 1-3 m in crystalline rock. The investigation range obtained in the Stripa granite is approximately 100 m in the single-hole mode and 200-300 m in the cross-hole model. Variations in the arrival time and amplitude of the direct wave between transmitter and receiver have been used for cross-hole tomographic imaging to yield maps of radar velocity and attenuation. The cross-hole measurement configuration coupled with tomographic inversion has less resolution than the reflection methods but provides better quantitative estimates of the values of measured properties. The analysis of the radar data has provided a consistent description of the fracture zones at the Stripa Cross-hole site in agreement with both geological and geophysical observations

  7. Fracturing Fluid Leak-off for Deep Volcanic Rock in Zhungeer Basin: Mechanism and Control Method

    OpenAIRE

    Huang Bo; Cheng Hao; He Yidong; Fu Yanming

    2017-01-01

    The deep volcanic reservoir in Zhungeer Basin is buried in over 4000m depth, which is characterized by complex lithology (breccia, andesite, basalt, etc.), high elastic modulus and massive natural fractures. During hydraulic fracturing, hydraulic fracture will propagate and natural fractures will be triggered by the increasing net pressure. However, the extension of fractures, especially natural fractures, would aggravate the leak-off effect of fracturing fluid, and consequently decrease the ...

  8. An Experimental Investigation into Failure and Localization Phenomena in the Extension to Shear Fracture Transition in Rock

    Science.gov (United States)

    Choens, R. C., II; Chester, F. M.; Bauer, S. J.; Flint, G. M.

    2014-12-01

    Fluid-pressure assisted fracturing can produce mesh and other large, interconnected and complex networks consisting of both extension and shear fractures in various metamorphic, magmatic and tectonic systems. Presently, rock failure criteria for tensile and low-mean compressive stress conditions is poorly defined, although there is accumulating evidence that the transition from extension to shear fracture with increasing mean stress is continuous. We report on the results of experiments designed to document failure criteria, fracture mode, and localization phenomena for several rock types (sandstone, limestone, chalk and marble). Experiments were conducted in triaxial extension using a necked (dogbone) geometry to achieve mixed tension and compression stress states with local component-strain measurements in the failure region. The failure envelope for all rock types is similar, but are poorly described using Griffith or modified Griffith (Coulomb or other) failure criteria. Notably, the mode of fracture changes systematically from pure extension to shear with increase in compressive mean stress and display a continuous change in fracture orientation with respect to principal stress axes. Differential stress and inelastic strain show a systematic increase with increasing mean stress, whereas the axial stress decreases before increasing with increasing mean stress. The stress and strain data are used to analyze elastic and plastic strains leading to failure and compare the experimental results to predictions for localization using constitutive models incorporating on bifurcation theory. Although models are able to describe the stability behavior and onset of localization qualitatively, the models are unable to predict fracture type or orientation. Constitutive models using single or multiple yield surfaces are unable to predict the experimental results, reflecting the difficulty in capturing the changing micromechanisms from extension to shear failure. Sandia

  9. Interpretation of tracer tests performed in fractured rock of the Lange Bramke basin, Germany

    Science.gov (United States)

    Maloszewski, Piotr; Herrmann, Andreas; Zuber, Andrzej

    Two multitracer tests performed in one of the major cross-fault zones of the Lange Bramke basin (Harz Mountains, Germany) confirm the dominant role of the fault zone in groundwater flow and solute transport. Tracers having different coefficients of molecular diffusion (deuterium, bromide, uranine, and eosine) yielded breakthrough curves that can only be explained by a model that couples the advective-dispersive transport in the fractures with the molecular diffusion exchange in the matrix. For the scale of the tests (maximum distance of 225m), an approximation was used in which the influence of adjacent fractures is neglected. That model yielded nearly the same rock and transport parameters for each tracer, which means that the single-fracture approximation is acceptable and that matrix diffusion plays an important role. The hydraulic conductivity of the fault zone obtained from the tracer tests is about 1.5×10-2m/s, whereas the regional hydraulic conductivity of the fractured rock mass is about 3×10-7m/s, as estimated from the tritium age and the matrix porosity of about 2%. These values show that the hydraulic conductivity along the fault is several orders of magnitude larger than that of the remaining fractured part of the aquifer, which confirms the dominant role of the fault zones as collectors of water and conductors of fast flow. Résumé Deux multitraçages ont été réalisés dans l'une des zones principales de failles du bassin de Lange Bramke (massif du Harz, Allemagne); les résultats confirment le rôle prédominant de la zone de failles pour l'écoulement souterrain et le transport de soluté. Les traceurs, possédant des coefficients de diffusion différents (deutérium, bromure, uranine et éosine), ont fourni des courbes de restitution qui ne peuvent être expliquées que par un modèle qui associe un transport advectif-dispersif dans les fractures à un échange par diffusion moléculaire dans la matrice. A l'échelle des expériences (distance

  10. Changes of the groundwater composition in fractured rocks of low permeability as a consequence of deglaciation

    International Nuclear Information System (INIS)

    Delos, A.; Duro, L.; Guimera, J.; Bruno, J.; Puigdomenech, I.

    2005-01-01

    ) Effects of ice melting and redox front migration in fractured rocks of low permeability. SKB TR-99-19, 86 pp [3] Gascoyne, M. (1999) Long-term maintenance of reducing conditions in a spent nuclear fuel repository. A re-examination of critical factors. SKB R 99-41, 56 pp. (authors)

  11. Conceptual characterization of the system of fractures of the rock mass known as Sierra del Medio (Chubut)

    International Nuclear Information System (INIS)

    Ventura, M.A.

    1990-01-01

    This work characterizes conceptually the system of fractures of the rock mass known as Sierra del Medio and its surroundings. The purpose of this characterization is to define the spectra of flow regimes which must be covered in computational models to be used in the prediction of the thermohydraulic effects of the eventual emplacement of a high-level radioactive waste repository. The analysis of the available data from previous studies was performed in order to determine qualitative data to be used in the stage of feasibility studied. The flow of water roughly N-S is defined by two systems of vertical, almost orthogonal fractures and surrounded by large faults. A set of hypotheses were considered which allow, supposing a given distribution of surface fractures, to establish the variations according to depth. The usual ways of obtaining the permeability and the hydraulic conductivity in fractured porous media are summarized in an appendix. (Author) [es

  12. Combined interpretation of radar, hydraulic, and tracer data from a fractured-rock aquifer near Mirror Lake, New Hampshire, USA

    Science.gov (United States)

    Day-Lewis, F. D.; Lane, J.W.; Gorelick, S.M.

    2006-01-01

    An integrated interpretation of field experimental cross-hole radar, tracer, and hydraulic data demonstrates the value of combining time-lapse geophysical monitoring with conventional hydrologic measurements for improved characterization of a fractured-rock aquifer. Time-lapse difference-attenuation radar tomography was conducted during saline tracer experiments at the US Geological Survey Fractured Rock Hydrology Research Site near Mirror Lake, Grafton County, New Hampshire, USA. The presence of electrically conductive saline tracer effectively illuminates permeable fractures or pathways for geophysical imaging. The geophysical results guide the construction of three-dimensional numerical models of ground-water flow and solute transport. In an effort to explore alternative explanations for the tracer and tomographic data, a suite of conceptual models involving heterogeneous hydraulic conductivity fields and rate-limited mass transfer are considered. Calibration data include tracer concentrations, the arrival time of peak concentration at the outlet, and steady-state hydraulic head. Results from the coupled inversion procedure suggest that much of the tracer mass migrated outside the three tomographic image planes, and that solute is likely transported by two pathways through the system. This work provides basic and site-specific insights into the control of permeability heterogeneity on ground-water flow and solute transport in fractured rock. ?? Springer-Verlag 2004.

  13. Modeling reactive transport processes in fractured rock using the time domain random walk approach within a dual-porosity framework

    Science.gov (United States)

    Roubinet, D.; Russian, A.; Dentz, M.; Gouze, P.

    2017-12-01

    Characterizing and modeling hydrodynamic reactive transport in fractured rock are critical challenges for various research fields and applications including environmental remediation, geological storage, and energy production. To this end, we consider a recently developed time domain random walk (TDRW) approach, which is adapted to reproduce anomalous transport behaviors and capture heterogeneous structural and physical properties. This method is also very well suited to optimize numerical simulations by memory-shared massive parallelization and provide numerical results at various scales. So far, the TDRW approach has been applied for modeling advective-diffusive transport with mass transfer between mobile and immobile regions and simple (theoretical) reactions in heterogeneous porous media represented as single continuum domains. We extend this approach to dual-continuum representations considering a highly permeable fracture network embedded into a poorly permeable rock matrix with heterogeneous geochemical reactions occurring in both geological structures. The resulting numerical model enables us to extend the range of the modeled heterogeneity scales with an accurate representation of solute transport processes and no assumption on the Fickianity of these processes. The proposed model is compared to existing particle-based methods that are usually used to model reactive transport in fractured rocks assuming a homogeneous surrounding matrix, and is used to evaluate the impact of the matrix heterogeneity on the apparent reaction rates for different 2D and 3D simple-to-complex fracture network configurations.

  14. Development of the numerical model for reactive transport of radionuclide and bacteria in the single fractured rock

    International Nuclear Information System (INIS)

    Kim, Jung Woo; Baik, Min Hoon

    2010-12-01

    On the aspects of safety case of HLW deep geological disposal system, recently, many researchers in the world have been actively studying about the bacterial effects on the radionuclide transport in the fractured rock. However, the domestic research level related on the area is still insufficient. Therefore, the objective of the research is to introduce the theory and development process of the numerical model, which was newly developed to examine the bacterial effects on the radionuclide transport in the single fractured rock, and to test the model by simulating in some imaginary conditions. From the verification by comparing the simulation results with analytical solution considering only solute transport and rock diffusion, the Pearson's correlation coefficient was greater than 0.99 which demonstrates the accuracy of the model. Since the simulation in the model domain of the single fractured core rock resulted in well-matched mass-balances for all solutes, the robustness and stability of the model could be proved again. Therefore, it is expected that the report can guide the potential model users and can be a referring material for a model developer who is trying to expand and/or update the model

  15. ADVANCED CHARACTERIZATION OF FRACTURED RESERVOIRS IN CARBONATE ROCKS: THE MICHIGAN BASIN

    Energy Technology Data Exchange (ETDEWEB)

    James R. Wood; William B. Harrison

    2002-12-01

    Michigan Basin, and it is crucial in developing reservoir quality rocks in some fields. Data on the occurrence of dolomite was extracted from driller's reports for all reported occurrences in Michigan, nearly 50 fields and over 500 wells. A digital database was developed containing the geographic location of all these wells (latitude-longitude) as well as the elevation of the first encounter of dolomite in the field/reservoir. Analysis shows that these dolomite occurrences are largely confined to the center of the basin, but with some exceptions, such as N. Adams Field. Further, some of the dolomite occurrences show a definite relationship to the fracture pattern described above, suggesting a genetic relationship that needs further work. Other accomplishments of this past reporting period include obtaining a complete land grid for the State of Michigan and further processing of the high and medium resolution DEM files. We also have measured new fluid inclusion data on dolomites from several fields that suggest that the dolomitization occurred at temperatures between 100 and 150 C. Finally, we have extracted the lithologic data for about 5000 wells and are in the process of integrating this data into the overall model for the Michigan Basin.

  16. Contaminant transport in fracture networks with heterogeneous rock matrices. The Picnic code

    International Nuclear Information System (INIS)

    Barten, Werner; Robinson, Peter C.

    2001-02-01

    timescales. To account for one-dimensional matrix diffusion into homogeneous planar or cylindrical rock layers, analytical relations in the Laplace domain are used. To deal with one-dimensional or two-dimensional matrix diffusion into heterogeneous rock matrices, a finite-element method is embedded. The capability of the code for handling two-dimensional matrix diffusion is - to our knowledge - unique in fracture network modelling. To ensure the reliability of the code, which merges methods from graph theory, Laplace transformation, finite-element methods, analytical and algebraic transformations and a convolution to calculate complex radionuclide transport processes over a large and diverse application range, implementation of the code and careful verification have been alternated for iterative improvement and especially the elimination of bugs. The internal mathematical structure of PICNIC forms the basis of the verification strategy. The code is verified in a series of seven steps with increasing complexity of the rock matrix. Calculations for single nuclides and nuclide decay chains are carefully tested and analysed for radionuclide transport in single legs, in pathways and in networks. Different sources and boundary conditions are considered. Quantitative estimates of the accuracy of the code are derived from comparisons with analytical solutions, cross-comparisons with other codes and different types of self -consistency tests, including extended testing of different refinements of the embedded finite- element method for different rock matrix geometries. The geosphere barrier efficiency is a good single indicator of the code accuracy. Application ranges with reduced accuracy of the code are also considered. For one-dimensional matrix diffusion into homogeneous and heterogeneous rock matrices, cross-comparisons with other codes are performed. For two-dimensional matrix diffusion, however, no code for cross-comparison is available. Consequently, the verification for

  17. Contaminant transport in fracture networks with heterogeneous rock matrices. The Picnic code

    Energy Technology Data Exchange (ETDEWEB)

    Barten, Werner [Paul Scherrer Inst., CH-5232 Villigen PSI (Switzerland); Robinson, Peter C. [QuantiSci Limited, Henley-on-Thames (United Kingdom)

    2001-02-01

    different timescales. To account for one-dimensional matrix diffusion into homogeneous planar or cylindrical rock layers, analytical relations in the Laplace domain are used. To deal with one-dimensional or two-dimensional matrix diffusion into heterogeneous rock matrices, a finite-element method is embedded. The capability of the code for handling two-dimensional matrix diffusion is - to our knowledge - unique in fracture network modelling. To ensure the reliability of the code, which merges methods from graph theory, Laplace transformation, finite-element methods, analytical and algebraic transformations and a convolution to calculate complex radionuclide transport processes over a large and diverse application range, implementation of the code and careful verification have been alternated for iterative improvement and especially the elimination of bugs. The internal mathematical structure of PICNIC forms the basis of the verification strategy. The code is verified in a series of seven steps with increasing complexity of the rock matrix. Calculations for single nuclides and nuclide decay chains are carefully tested and analysed for radionuclide transport in single legs, in pathways and in networks. Different sources and boundary conditions are considered. Quantitative estimates of the accuracy of the code are derived from comparisons with analytical solutions, cross-comparisons with other codes and different types of self -consistency tests, including extended testing of different refinements of the embedded finite- element method for different rock matrix geometries. The geosphere barrier efficiency is a good single indicator of the code accuracy. Application ranges with reduced accuracy of the code are also considered. For one-dimensional matrix diffusion into homogeneous and heterogeneous rock matrices, cross-comparisons with other codes are performed. For two-dimensional matrix diffusion, however, no code for cross-comparison is available. Consequently, the

  18. Giving peeps to my props: Using 3D printing to shed new light on particle transport in fractured rock.

    Science.gov (United States)

    Walsh, S. D.; Du Frane, W. L.; Vericella, J. J.; Aines, R. D.

    2014-12-01

    Smart tracers and smart proppants promise new methods for sensing and manipulating rock fractures. However, the correct use and interpretation of these technologies relies on accurate models of their transport. Even for less exotic particles, the factors controlling particle transport through fractures are poorly understood. In this presentation, we will describe ongoing research at Lawrence Livermore National Laboratory into the transport properties of particles in natural rock fractures. Using three dimensional printing techniques, we create clear-plastic reproductions of real-world fracture surfaces, thereby enabling direct observation of the particle movement. We will also discuss how particle tracking of dense particle packs can be further enhanced by using such specially tailored flow cells in combination with micro-encapsulated tracer particles. Experimental results investigating the transport behavior of smart tracers and proppants close to the neutrally buoyant limit will be presented and we will describe how data from these experiments can be used to improve large-scale models of particle transport in fractures. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  19. Integrated Analytic Radionuclide Transport Model for a Spent Nuclear Fuel Repository in Saturated Fractured Rock

    International Nuclear Information System (INIS)

    Hedin, Allan

    2002-01-01

    Simple analytic expressions are presented for radionuclide transport from a KBS 3-type repository, where spent nuclear fuel is placed in copper canisters surrounded by bentonite clay and deposited at a depth of 500 m in fractured granitic rock.Dissolution of readily accessible and fuel matrix embedded nuclides, chain decay, and nuclide precipitation is treated within the canister. Transport in the canister void and buffer is modeled with a dual stirred tank analogy, where transport resistances represent an assumed small initial damage in the canister and transport features of the buffer-geosphere interface. Initial, transient diffusion in the buffer is treated with a simple correction term. Chain decay is not included in the buffer.Geosphere transport expressions handle advection, longitudinal dispersion, matrix diffusion, sorption, and radioactive decay, but not chain decay. The treatment is based on earlier results for an instantaneous inlet and for a constant inlet to the geosphere in the nondispersive case. A correction is added so that longitudinal dispersion is taken approximately into account. The correction utilizes analytical expressions for the temporal moments of the geosphere release curve in the dispersive case.The near-field/geosphere integration is treated in a simplified manner avoiding numerical convolutions. The instantaneous inlet expression for the geosphere release is used when the near-field release decreases rapidly in comparison to a typical response time in the geosphere; the constant inlet expression is used in the opposite case.Twenty-seven calculation cases from a safety assessment of a KBS 3 repository using borehole data from three different field investigation sites were repeated with the analytic expressions. The agreement in both near-field and geosphere releases is in general well within an order of magnitude for the variety of long- and short-lived, sorbing, nonsorbing, solubility limited, immediately accessible, and fuel matrix

  20. Distinct element method modeling of fracture behavior in near field rock

    International Nuclear Information System (INIS)

    Hoekmark, H.

    1990-12-01

    This report concerns the numerical calculations of the behavior of the near field of a nuclear waste repository. The calculations were performed using the two-dimensional distinct element code UDEC. The distinct element method accounts specifically for discontinuities, e.g. fractures that intersect the model region. It is shown that, if an appropriate joint constitutive relation is applied, the calculated joint behavior can be brought in close agreement with empirically derived stress-strain relations. Three basic geometries are studied, namely a vertical tunnel section, a horizontal borehole section and a combination, i.e. a vertical section of tunnel and deposition hole. The effects of different processes and activities are investigated, e.g. effects of excavations, of thermal loads, of internal tunnel pressures and of pore pressures and fracture flow resulting from the hydraulic ground water pressure. The interpretation of the results concerns in particular joint behavior, especially joint openings, in the nearest surroundings of excavations and of thermally affected regions. The calculations show that joint shear and joint normal displacements induced by excavation and by thermal processes may be considerable, and that thermal cycles may result in residual joint aperture changes, especially in systems with loosely bound rock blocks. It is concluded that the UDEC code, when applied to problems that have a two-dimensional character, gives results that are probably quantitatively correct. The results appear to be strongly dependant on the detailed joint structure close to free boundaries such as tunnel walls, which indicated that the 3-D situation regarding joint orientation might have to be considered. It is recommended that 3-D calculations should be performed to verify and quantitatively interpret the 2-D results and to analyze situations that are actually three-dimensional. (au)

  1. Geochemical Interaction of Middle Bakken Reservoir Rock and CO2 during CO2-Based Fracturing

    Science.gov (United States)

    Nicot, J. P.; Lu, J.; Mickler, P. J.; Ribeiro, L. H.; Darvari, R.

    2015-12-01

    This study was conducted to investigate the effects of geochemical interactions when CO2 is used to create the fractures necessary to produce hydrocarbons from low-permeability Middle Bakken sandstone. The primary objectives are to: (1) identify and understand the geochemical reactions related to CO2-based fracturing, and (2) assess potential changes of reservoir property. Three autoclave experiments were conducted at reservoir conditions exposing middle Bakken core fragments to supercritical CO2 (sc-CO2) only and to CO2-saturated synthetic brine. Ion-milled core samples were examined before and after the reaction experiments using scanning electron microscope, which enabled us to image the reaction surface in extreme details and unambiguously identify mineral dissolution and precipitation. The most significant changes in the reacted rock samples exposed to the CO2-saturated brine is dissolution of the carbonate minerals, particularly calcite which displays severely corrosion. Dolomite grains were corroded to a lesser degree. Quartz and feldspars remained intact and some pyrite framboids underwent slight dissolution. Additionally, small amount of calcite precipitation took place as indicated by numerous small calcite crystals formed at the reaction surface and in the pores. The aqueous solution composition changes confirm these petrographic observations with increase in Ca and Mg and associated minor elements and very slight increase in Fe and sulfate. When exposed to sc-CO2 only, changes observed include etching of calcite grain surface and precipitation of salt crystals (halite and anhydrite) due to evaporation of residual pore water into the sc-CO2 phase. Dolomite and feldspars remained intact and pyrite grains were slightly altered. Mercury intrusion capillary pressure tests on reacted and unreacted samples shows an increase in porosity when an aqueous phase is present but no overall porosity change caused by sc-CO2. It also suggests an increase in permeability

  2. Characterization and evaluation of sites for deep geological disposal of radioactive waste in fractured rocks. Proceedings

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-09-01

    The third Aespoe International Seminar was organised by SKB to assess the state of the art in characterisation and evaluation of sites for deep geological disposal of radioactive waste in fractured rocks. Site characterisation and evaluation are important elements for determining the site suitability and long-term safety of a geological repository for radioactive waste disposal. Characterisation work also provides vital information for the design of the underground facility and the engineered barrier system that will contain the waste. The aim of the seminar was to provide a comprehensive assessment of the current know-how on this topic based on world-wide experience from more than 20 years of characterisation and evaluation work. The seminar, which was held at the Aespoe Hard Rock Laboratory was attended by 72 scientists from 10 different countries. The program was divided into four sessions of which two were run in parallel. A total of 38 oral and 5 poster presentations were given at the seminar. The presentations gave a comprehensive summary of recently completed and current work on site characterisation, modelling and application in performance assessments. The results presented at the seminar generally show that significant progress has been made in this field during the last decade. New characterisation techniques have become available, strategies for site investigations have developed further, and model concepts and codes have reached new levels of refinement. Data obtained from site characterisation have also successfully been applied in several site specific performance assessments. The seminar clearly showed that there is a solid scientific basis for assessing the suitability of sites for actual repositories based on currently available site characterisation technology and modelling capabilities. Separate abstracts have been prepared for 38 of the presentations

  3. Red-staining of the wall rock and its influence on the reducing capacity around water conducting fractures

    International Nuclear Information System (INIS)

    Drake, Henrik; Tullborg, Eva-Lena; Annersten, Hans

    2008-01-01

    Red-staining and alteration of wall rock is common around water conducting fractures in the Laxemar-Simpevarp area (SE Sweden), which is currently being investigated by the Swedish Nuclear Fuel and Waste Management Co. (SKB) in common with many other places. Red-staining is often interpreted as a clear sign of oxidation but relevant analyses are seldom performed. The area is dominated by Palaeoproterozoic crystalline rocks ranging in composition from quartz monzodiorite to granite. In this study wall rock samples have been compared with reference samples from within 0.1 to 1 m of the red-stained rock, in order to describe mineralogical and geochemical changes but also changes in redox conditions. A methodology for tracing changes in mineralogy, mineral and whole rock chemistry and Fe 3+ /Fe tot ratio in silicates and oxides in the red-stained wall rock and the reference rock is reported. The results show that the red-stained rock adjacent to the fractures displays major changes in mineralogy; biotite, plagioclase and magnetite have been altered and chlorite, K-feldspar, albite, sericite, prehnite, epidote and hematite have been formed. The changes in chemistry are however moderate; K-enrichment, Ca-depletion and constant Fe tot are documented. The Fe 3+ /Fe tot ratio in the oxide phase is higher in the red-stained samples whereas the Fe 3+ /Fe tot ratio in the silicate phase is largely similar in the wall rock and the reference samples. Because most of the Fe is hosted in the silicate phase the decrease in reducing capacity (Fe 2+ ), if any, in the red-stained wall rock is very small and not as high as macroscopic observations might suggest. Instead, the mineralogical changes in combination with the modest oxidation and formation of minute hematite grains in porous secondary minerals in pseudomorphs after plagioclase have produced the red-staining. Increased porosity is also characteristic for the red-stained rock. Moderate alteration in the macroscopically fresh

  4. Water-level fluctuations due to Earth tides in a well pumping from slightly fractured crystalline rock

    International Nuclear Information System (INIS)

    Marine, I.W.

    1975-01-01

    At the Savannah River plant of the Atomic Energy Commission near Aiken, South Carolina, there are three distinct groundwater systems: the coastal plain sediments, the crystalline metamorphic rocks, and a buried Triassic basin. The coastal plain sediments include several Cretaceous and Tertiary granular aquifers and aquicludes, the total thickness being about 305 m. Below these sediments, water occurs in small fractures in crystalline metamorphic rock (hornblende schist and gneiss with lesser amounts of quartzite). Water level fluctuations due to earth tides are recorded in the crystalline metamorphic rock system and in the coastal plain sediments. No water level fluctuations due to earth tides have been observed in wells in the Triassic rock because of the very low permeability. The water level fluctuations due to earth tides in the crystalline rock are about 10 cm, and those in the sediments are about 1.8 cm. The use of water level fluctuations due to earth tides to calculate porosity appears to present practical difficulties both in the crystalline metamorphic rock system and in the coastal plain sediments. In a 1-yr pumping test on a well in the crystalline metamorphic rock the flow was controlled to within 0.1 per cent of the total discharge, which was 0.94 l/s. The water level fluctuations due to earth tides in the pumping well were 10 cm, the same as when this well was not being pumped. (U.S.)

  5. Shape Memory Alloy Rock Splitters (SMARS) - A Non-Explosive Method for Fracturing Planetary Rocklike Materials and Minerals

    Science.gov (United States)

    Benafan, Othmane; Noebe, Ronald D.; Halsmer, Timothy J.

    2015-01-01

    A static rock splitter device based on high-force, high-temperature shape memory alloys (HTSMAs) was developed for space related applications requiring controlled geologic excavation in planetary bodies such as the Moon, Mars, and near-Earth asteroids. The device, hereafter referred to as the shape memory alloy rock splitter (SMARS), consisted of active (expanding) elements made of Ni50.3Ti29.7Hf20 (at.%) that generate extremely large forces in response to thermal input. The preshaping (training) of these elements was accomplished using isothermal, isobaric and cyclic training methods, which resulted in active components capable of generating stresses in excess of 1.5 GPa. The corresponding strains (or displacements) were also evaluated and were found to be 2 to 3 percent, essential to rock fracturing and/or splitting when placed in a borehole. SMARS performance was evaluated using a test bed consisting of a temperature controller, custom heaters and heater holders, and an enclosure for rock placement and breakage. The SMARS system was evaluated using various rock types including igneous rocks (e.g., basalt, quartz, granite) and sedimentary rocks (e.g., sandstone, limestone).

  6. Drift Scale Modeling: Study of Unsaturated Flow into a Drift Using a Stochastic Continuum Model

    International Nuclear Information System (INIS)

    Birkholzer, J.T.; Tsang, C.F.; Tsang, Y.W.; Wang, J.S

    1996-01-01

    Unsaturated flow in heterogeneous fractured porous rock was simulated using a stochastic continuum model (SCM). In this model, both the more conductive fractures and the less permeable matrix are generated within the framework of a single continuum stochastic approach, based on non-parametric indicator statistics. High-permeable fracture zones are distinguished from low-permeable matrix zones in that they have assigned a long range correlation structure in prescribed directions. The SCM was applied to study small-scale flow in the vicinity of an access tunnel, which is currently being drilled in the unsaturated fractured tuff formations at Yucca Mountain, Nevada. Extensive underground testing is underway in this tunnel to investigate the suitability of Yucca Mountain as an underground nuclear waste repository. Different flow scenarios were studied in the present paper, considering the flow conditions before and after the tunnel emplacement, and assuming steady-state net infiltration as well as episodic pulse infiltration. Although the capability of the stochastic continuum model has not yet been fully explored, it has been demonstrated that the SCM is a good alternative model feasible of describing heterogeneous flow processes in unsaturated fractured tuff at Yucca Mountain

  7. A new lumped-parameter approach to simulating flow processes in unsaturated dual-porosity media

    Energy Technology Data Exchange (ETDEWEB)

    Zimmerman, R.W.; Hadgu, T.; Bodvarsson, G.S. [Lawrence Berkeley Laboratory, CA (United States)

    1995-03-01

    We have developed a new lumped-parameter dual-porosity approach to simulating unsaturated flow processes in fractured rocks. Fluid flow between the fracture network and the matrix blocks is described by a nonlinear equation that relates the imbibition rate to the local difference in liquid-phase pressure between the fractures and the matrix blocks. This equation is a generalization of the Warren-Root equation, but unlike the Warren-Root equation, is accurate in both the early and late time regimes. The fracture/matrix interflow equation has been incorporated into a computational module, compatible with the TOUGH simulator, to serve as a source/sink term for fracture elements. The new approach achieves accuracy comparable to simulations in which the matrix blocks are discretized, but typically requires an order of magnitude less computational time.

  8. Laboratory investigation of shale rock to identify fracture propagation in vertical direction to bedding

    Science.gov (United States)

    Peng, Tan; Yan, Jin; Bing, Hou; Yingcao, Zhou; Ruxin, Zhang; Zhi, Chang; Meng, Fan

    2018-06-01

    Affected by beddings and natural fractures, fracture geometry in the vertical plane is complex in shale formation, which differs from a simple fracture in homogeneous sandstone reservoirs. However, the propagation mechanism of a hydraulic fracture in the vertical plane has not been well understood. In this paper, a true tri-axial pressure machine was deployed for shale horizontal well fracturing simulation experiments of shale outcrops. The effects of multiple factors on hydraulic fracture vertical propagation were studied. The results revealed that hydraulic fracture initiation and propagation displayed four basic patterns in the vertical plane of laminated shale formation. A hydraulic fracture would cross the beddings under the high vertical stress difference between a vertical stress and horizontal minimum stress of 12 MPa, while a hydraulic fracture propagates along the beddings under a low vertical stress difference of 3 MPa. Four kinds of fracture geometry, including a single main fracture, a nonplanar fracture, a complex fracture, and a complex fracture network, were observed due to the combined effects of flow rate and viscosity. Due to the influence of binding strength (or cementing strength) on the fracture communication effects between a hydraulic fracture and the beddings, the opening region of the beddings takes the shape of an ellipse.

  9. Sensitivity and uncertainty analyses applied to one-dimensional radionuclide transport in a layered fractured rock: MULTFRAC --Analytic solutions and local sensitivities

    International Nuclear Information System (INIS)

    Gureghian, A.B.; Wu, Y.T.; Sagar, B.

    1992-12-01

    Exact analytical solutions based on the Laplace transforms are derived for describing the one-dimensional space-time-dependent, advective transport of a decaying species in a layered, saturated rock system intersected by a planar fracture of varying aperture. These solutions, which account for advection in fracture, molecular diffusion into the rock matrix, adsorption in both fracture and matrix, and radioactive decay, predict the concentrations in both fracture and rock matrix and the cumulative mass in the fracture. The solute migration domain in both fracture and rock is assumed to be semi-infinite with non-zero initial conditions. The concentration of each nuclide at the source is allowed to decay either continuously or according to some periodical fluctuations where both are subjected to either a step or band release mode. Two numerical examples related to the transport of Np-237 and Cm-245 in a five-layered system of fractured rock were used to verify these solutions with several well established evaluation methods of Laplace inversion integrals in the real and complex domain. In addition, with respect to the model parameters, a comparison of the analytically derived local sensitivities for the concentration and cumulative mass of Np-237 in the fracture with the ones obtained through a finite-difference method of approximation is also reported

  10. Experimental and Numerical Studies on Development of Fracture Process Zone (FPZ) in Rocks under Cyclic and Static Loadings

    Science.gov (United States)

    Ghamgosar, M.; Erarslan, N.

    2016-03-01

    The development of fracture process zones (FPZ) in the Cracked Chevron Notched Brazilian Disc (CCNBD) monsonite and Brisbane tuff specimens was investigated to evaluate the mechanical behaviour of brittle rocks under static and various cyclic loadings. An FPZ is a region that involves different types of damage around the pre-existing and/or stress-induced crack tips in engineering materials. This highly damaged area includes micro- and meso-cracks, which emerge prior to the main fracture growth or extension and ultimately coalescence to macrofractures, leading to the failure. The experiments and numerical simulations were designed for this study to investigate the following features of FPZ in rocks: (1) ligament connections and (2) microcracking and its coalescence in FPZ. A Computed Tomography (CT) scan technique was also used to investigate the FPZ behaviour in selected rock specimens. The CT scan results showed that the fracturing velocity is entirely dependent on the appropriate amount of fracture energy absorbed in rock specimens due to the change of frequency and amplitudes of the dynamic loading. Extended Finite Element Method (XFEM) was used to compute the displacements, tensile stress distribution and plastic energy dissipation around the propagating crack tip in FPZ. One of the most important observations, the shape of FPZ and its extension around the crack tip, was made using numerical and experimental results, which supported the CT scan results. When the static rupture and the cyclic rupture were compared, the main differences are twofold: (1) the number of fragments produced is much greater under cyclic loading than under static loading, and (2) intergranular cracks are formed due to particle breakage under cyclic loading compared with smooth and bright cracks along cleavage planes under static loading.

  11. Scale effect experiment in a fractured rock mass. Pilot study in the certified Fanay-Augeres mine (F)

    International Nuclear Information System (INIS)

    Durand, E.; Peaudecerf, P.; Ledoux, E.; De Marsily, G.

    1985-01-01

    This report (in two volumes) presents the results of a first phase of research about ''scale effect'' on permeability and solute transport in a fractured rock mass, to assess its suitability for future disposal of radioactive wastes. The gallery which was ''certified'' is located in the Fanay-Augeres mine(F), at a depth of about 175 m, in a granite mass. The portion selected for the subsequent experimental work is about 100 m long

  12. Environmental tracers as indicators of groundwater flow and evolution in a fractured rock aquifer, Clare Valley, South Australia

    International Nuclear Information System (INIS)

    Love, A.J.; Cook, P.G.; Herczeg, A.L.; Simmons, C.T.

    1999-01-01

    Environmental tracers, chemistry and hydraulic data have been used to develop a conceptual model for groundwater flow in a fractured rock aquifer, at Clare, South Australia. In the upper 36 m there is relatively high horizontal flow, closely spaced fractures and large apertures. Below 36 m, horizontal flow rates are less and apertures become smaller. A sub horizontal fracture at 36 m separates the upper system from flow systems below. There is minimum vertical connection of groundwater above and below 36 m as indicated by low hydraulic conductivity and a steep 14 C concentration gradient. The observed linear trends in chemistry and isotope data are a result of mixing between old saline water and relatively younger fresh water. Greater mixing has occurred in the upper 36 m, with the amount of mixing diminishing with depth. We propose that this mixing is a recent process that has been triggered as a result of increased recharge to the system since the clearing of native vegetation approximately 100 years ago. Increased recharge of lower salinity water has resulted in the establishment of concentration gradients between the matrix and the fractures. This has resulted in diffusion of relatively immobile water in the matrix into relatively fast moving water in the fractures. Greater flushing has occurred in the upper 36 m due greater fracture density and larger apertures and higher horizontal flow rates. (author)

  13. A gas migration test in saturated, fractured rock - final report for the joint UKDOE/AECL project, phase 2

    International Nuclear Information System (INIS)

    Gascoyne, M.; Wuschke, D.M.; Brown, A.; Hayles, J.G.; Kozak, E.T.; Lodha, G.S.; Thorne, G.A.

    1991-12-01

    Helium gas was injected at constant pressure into an inclined fracture zone through an access borehole at a depth of about 40 m, in the Lac du Bonnet granite, southeastern Manitoba. The gas flow rate, arrival time and pattern of distribution of gas at the surface were monitored by soil gas surveys. The field results were compared with predictions of a simple analytical model derived from Thunvik and Braester (1987). Good agreement was found when the influence of vertical fracturing in the bedrock and a low-permeability overburden were included in the model. The model was then used to determined the hydraulic conductivity of individual gas flow paths in the fractured rock. (author). 23 refs., 5 tabs., 37 figs

  14. Geologic character of tuffs in the unsaturated zone at Yucca Mountain, southern Nevada

    International Nuclear Information System (INIS)

    Scott, R.B.; Spengler, R.W.; Diehl, S.; Lappin, A.R.; Chornack, M.P.

    1982-01-01

    At Yucca Mountain, a potential site for a high-level nuclear waste repository on the Nevada Test Site in southern Nevada, evaluation of the geologic setting and rock physical properties, along with previous regional hydrologic studies, has provided background that can be used for construction of a preliminary conceptual hydrologic model of the unsaturated zone. The 500-m-thick unsaturated portion of Yucca Mountain consists of alternating layers of two contrasting types of tuff. One type consists of highly fractured, densely welded, relatively nonporous but highly transmissive ash-flow tuffs. The other type consists of relatively unfractured, nonwelded, highly porous but relatively nontransmissive, argillic and zeolitic bedded tuffs and ash-flow tuffs. The contrast between these two sets of distinctive physical properties results in a stratified sequence best described as ''physical-property stratigraphy'' as opposed to traditional petrologic stratigraphy of volcanic rocks. The vast majority of recharge through the unsaturated zone is assumed to be vertical; the dominant migration may occur in fractures of densely welded tuffs and in the matrix of nonwelded tuff, but the mode of fluid flow in these unsaturated systems is undetermined. Limited lateral flow of recharge may occur at horizons where local perched water tables may exist above relatively nontransmissive zeolitized nonwelded tuffs. The pervasive north-northwest-striking fractures may control the direction of lateral flow of recharge, if any, in the unsaturated zone, and certainly that direction coincides closely with the observed southeasterly flow direction in the saturated zone under Yucca Mountain. Empirical evaluation of this conceptual hydrologic model has begun. 41 refs., 18 figs., 2 tabs

  15. Geologic character of tuffs in the unsaturated zone at Yucca Mountain, southern Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Scott, R.B.; Spengler, R.W.; Diehl, S.; Lappin, A.R.; Chornack, M.P.

    1982-12-31

    At Yucca Mountain, a potential site for a high-level nuclear waste repository on the Nevada Test Site in southern Nevada, evaluation of the geologic setting and rock physical properties, along with previous regional hydrologic studies, has provided background that can be used for construction of a preliminary conceptual hydrologic model of the unsaturated zone. The 500-m-thick unsaturated portion of Yucca Mountain consists of alternating layers of two contrasting types of tuff. One type consists of highly fractured, densely welded, relatively nonporous but highly transmissive ash-flow tuffs. The other type consists of relatively unfractured, nonwelded, highly porous but relatively nontransmissive, argillic and zeolitic bedded tuffs and ash-flow tuffs. The contrast between these two sets of distinctive physical properties results in a stratified sequence best described as "physical-property stratigraphy" as opposed to traditional petrologic stratigraphy of volcanic rocks. The vast majority of recharge through the unsaturated zone is assumed to be vertical; the dominant migration may occur in fractures of densely welded tuffs and in the matrix of nonwelded tuff, but the mode of fluid flow in these unsaturated systems is undetermined. Limited lateral flow of recharge may occur at horizons where local perched water tables may exist above relatively nontransmissive zeolitized nonwelded tuffs. The pervasive north-northwest-striking fractures may control the direction of lateral flow of recharge, if any, in the unsaturated zone, and certainly that direction coincides closely with the observed southeasterly flow direction in the saturated zone under Yucca Mountain. Empirical evaluation of this conceptual hydrologic model has begun. 41 refs., 18 figs., 2 tabs.

  16. Three-dimensional modeling of unsaturated flow in the vicinity of proposed exploratory shaft facilities at Yucca Mountain, Nevada

    International Nuclear Information System (INIS)

    Rockhold, M.L.; Sagar, B.; Connelly, M.P.

    1992-04-01

    This report describes the results of a study to investigate the influence of proposed exploratory shafts on the moisture distribution within unsaturated, fractured rock at Yucca Mountain, Nevada. The long-term effects of exploratory shafts at Yucca Mountain are important in the estimation of potential waste migration and fate, while short-term effects may be important in the planning and interpretation of tests performed at the site. The PORFLO-3 computer code was used for simulation of moisture flow through the geologic units adjacent to the ESF. Rather than represent fractures as discrete elements, an equivalent continuum was stipulated, in which the fractured units were assigned equivalent or composite hydrologic properties. Explicit treatment of fractures is not feasible because of the extremely large number of fractures contained in the site-scale problem and the difficulties in characterizing and modeling the fracture geometries

  17. Observations from borehole dilution logging experiments in fractured crystalline rock under variable hydraulic conditions

    Science.gov (United States)

    Harte, Philip T.; Anderson, Alton; Williams, John H.

    2014-01-01

    Identifying hydraulically active fractures in low permeability, crystalline-bedrock aquifers requires a variety of geophysical and hydrogeophysical borehole tools and approaches. One such approach is Single Borehole Dilution Tests (SBDT), which in some low flow cases have been shown to provide greater resolution of borehole flow than other logging procedures, such as vertical differential Heat Pulse Flowmeter (HPFM) logging. Because the tools used in SBDT collect continuous profiles of water quality or dye changes, they can identify horizontal flow zones and vertical flow. We used SBDT with a food grade blue dye as a tracer and dual photometer-nephelometer measurements to identify low flow zones.SBDT were conducted at seven wells with open boreholes (exceeding 300 ft). At most of the wells HPFM logs were also collected. The seven wells are set in low-permeability, fractured granite and gneiss rocks underlying a former tetrachloroeythylene (PCE) source area at the Savage Municipal Well Superfund site in Milford, NH. Time series SBDT logs were collected at each of the seven wells under three distinct hydraulic conditions: (1) ambient conditions prior to a pump test at an adjacent well, (2) mid test, after 2-3 days of the start of the pump test, and (3) at the end of the test, after 8-9 days of the pump test. None of the SBDT were conducted under pumping conditions in the logged well. For each condition, wells were initially passively spiked with blue dye once and subsequent time series measurements were made.Measurement accuracy and precision of the photometer tool is important in SBDT when attempting to detect low rates of borehole flow. Tests indicate that under ambient conditions, none of the wells had detectable flow as measured with HPFM logging. With SBDT, 4 of the 7 showed the presence of some very low flow. None of 5 (2 of the 7 wells initially logged with HPFM under ambient conditions were not re-logged) wells logged with the HPFM during the pump test had

  18. Grouting design based on characterization of the fractured rock. Presentation and demonstration of a methodology

    Energy Technology Data Exchange (ETDEWEB)

    Fransson, Aasa (SWECO Environment, Stockholm (Sweden); Chalmers Univ. of Technology, Goeteborg (Sweden))

    2008-12-15

    The design methodology presented in this document is based on an approach that considers the individual fractures. The observations and analyses made during production enable the design to adapt to the encountered conditions. The document is based on previously published material and overview flow charts are used to show the different steps. Parts of or the full methodology has been applied for a number of tunneling experiments and projects. SKB projects in the Aespoe tunnel include a pillar experiment and pre-grouting of a 70 meter long tunnel (TASQ). Further, for Hallandsas railway tunnel (Skaane south Sweden), a field pre-grouting experiment and design and post-grouting of a section of 133 meters have been made. For the Nygard railway tunnel (north of Goeteborg, Sweden), design and grouting of a section of 86 meters (pre-grouting) and 60 meters (post-grouting) have been performed. Finally, grouting work at the Tornskog tunnel (Stockholm, Sweden) included design and grouting along a 100 meter long section of one of the two tunnel tubes. Of importance to consider when doing a design and evaluating the result are: - The identification of the extent of the grouting needed based on inflow requirements and estimates of tunnel inflow before grouting. - The selection of grout and performance of grouting materials including penetration ability and length. The penetration length is important for the fan geometry design. - The ungrouted compared to the grouted and excavated rock mass conditions: estimates of tunnel inflow and (if available) measured inflows after grouting and excavation. Identify if possible explanations for deviations. For the Hallandsas, Nygard and Tornskog tunnel sections, the use of a Pareto distribution and the estimate of tunnel inflow identified a need for sealing small aperture f