| 1. |
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| 2. |
- Andersson, J. C., et al.
(författare)
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Modeling the Äspö Pillar stability experiment
- 2010
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Ingår i: Rock Mechanics in Civil and Environmental Engineering - Proceedings of the European Rock Mechanics Symposium, EUROCK 2010. - 9780415586542 ; , s. 787-790
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Konferensbidrag (refereegranskat)abstract
- This paper presents results of the 1st stages ofTaskAof the Decovalex 2011 project, the numerical modeling of the Äspö Pillar Stability experiment performed by the Äspö Hard Rock Laboratory of the Swedish Nuclear Fuel and Waste Management Company (SKB). The objective is to perform back calculation of the Äspö pillar behavior using state of the art numerical modeling techniques for the material behavior. The work is divided into three stages and it is the first stage of thework that will be presented in this paper. Seven international teams from six different countries participated in the task and contributed to the results presented in this paper, concerning back calculation of uniaxial and triaxial compressive core testing and elastic back calculation of the stress path for excavation-induced stresses. The results are useful for understanding the occurrence of spalling in the upper part of the pillar during excavation and the stress path modeling gives the first approximation of the yielding strength of the pillar. The calculated results agree well with observations measured during experiment.
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| 3. |
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| 4. |
- Baghbanan, Alireza, et al.
(författare)
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Hydraulic properties of fractured rock masses with correlated fracture length and aperture
- 2007
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Ingår i: International Journal of Rock Mechanics And Mining Sciences. - : Elsevier BV. - 1365-1609 .- 1873-4545. ; 44:5, s. 704-719
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Tidskriftsartikel (refereegranskat)abstract
- Permeability of fractured rocks is investigated considering the correlation between distributed fracture aperture and trace length, based on a newly developed correlation equation. The influence of the second moment of the lognormal distribution of apertures on the existence of representative elementary volume (REV), and the possibility of equivalent permeability tensor of the fractured rock mass, is examined by simulating flow through a large number of stochastic discrete fracture network (DFN) models of varying sizes and varying fracture properties. The REV size of the DFN models increases with the increase of the second moment of the lognormal distribution, for both the correlated and uncorrelated cases. The variation of overall permeability between different stochastic realizations is an order of magnitude larger when the aperture and length are correlated than when they are uncorrelated. The mean square error of the directional permeability increases with increasing value of the second moment of the lognormal distribution function, and good fitting to an ellipsis of permeability tensor can only be reached with very large sizes of DFN models, compared with the case of constant fracture aperture, regardless of fracture trace length.
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| 5. |
- Baghbanan, Alireza, 1971-
(författare)
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Scale and Stress Effects on Hydro-Mechanical Properties of Fractured Rock Masses
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, the effects of size and stress on permeability, deformability and strength of fractured rock masses are investigated. A comparison study was carried out to examine the effects of considering, or not considering, the correlation between distributions of fracture apertures and fracture trace lengths on the hydro-mechanical behavior of fractured rocks. The basic concepts used are the fundamental principles of the general theory of elasticity, Representative Elementary Volume (REV), the tensor of equivalent permeability, and the strength criteria of the fractured rocks. Due to the size and stress dependence of the hydro-mechanical properties of rock fractures, the overall effective (or equivalent) hydro-mechanical properties of the fractured rocks are also size and stress-dependent. However, such dependence cannot be readily investigated in laboratory using small samples, and so numerical modeling becomes a necessary tool for estimating their impacts. In this study, a closed-form relation is established for representing the correlation between a truncated lognormal distribution of fracture apertures and a truncated power law distribution of trace lengths, as obtained from field mapping. Furthermore, a new nonlinear algorithm is developed for predicting the relationship between normal stress and normal displacement of fractures, based on the Bandis model and the correlation between aperture and length. A large number of stochastic Discrete Fracture Network (DFN) models of varying sizes were extracted from some generated large-sized parent realizations based on a realistic fracture system description from a site investigation programme at Sellafield, UK, for calculating the REV of hydro-mechanical properties of fractured rocks. Rotated DFN models were also generated and used for evaluation of the distributions of directional permeabilities, such that tensors of equivalent permeability could be established based on stochastically established REVs. The stress-dependence of the permeability and the stress-displacement behaviour were then investigated using models of REV sizes. The Discrete Element Method (DEM) was used for numerical simulation of the fluid flow, deformability properties and mechanical strength behavior of fractured rocks. The results show significant scale-dependency of rock permeability, deformability and strength, and its variation when the correlation between aperture and trace length of fractures are concerned, with the overall permeability and deformability more controlled by dominating fractures with larger apertures and higher transmissivity and deformability, compared with fracture network models having uniform aperture. As the second moment of aperture distribution increases, a fractured rock mass shows more discrete behavior and an REV is established in smaller value of second moment with much larger model size, compared with the models with uniform fracture aperture. When the fracture aperture pattern is more scattered, the overall permeability, Young’s modulus and mechanical strength change significantly. The effect of stress on permeability and fluid flow patterns in fractured rock is significant and can lead to the existence or non-existence of a permeability tensor. Stress changes the fluid flow patterns and can cause significant channeling and the permeability tensor, and REV may be destroyed or re-established at different applied stress conditions. With an increase in the confining stress on the DEM models, the strength is increased. Compared with the Hoek-Brown criterion, the Mohr-Coulomb strength envelope provides a better fit to the results of numerical biaxial compression tests, with significant changes of the strength characteristic parameters occurring when the second moment of the aperture distribution is increased.
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| 6. |
- Baghbanan, Alireza, et al.
(författare)
-
Scale and stress effects on permeability tensor of fractured rocks with correlated fracture length and aperture
- 2008
-
Ingår i: Thermo-Hydromechanical and chemical coupling in geomaterials and applications. - 9781848210431 ; , s. 439-446
-
Konferensbidrag (refereegranskat)abstract
- The effect of stress on permeability tensor and Representative Elementary Voliume (REV) of fractured rock masses is studied using a Discrete Element Approach (DEM). A new nonlinear model of rock fractures is developed for prediction of normal stress-normal displacement behavior of fractures based on the correlation between fracture aperture and length distributions. The results show that at small differential stress ratios K (=horizontal/vertical stresses) the overall permeability of fracture networks is generally decreased. However contribution from a few large fractures of higher hydraulic conductivity prevents drastic reduction of the overall permeability, compare with DFN models of constant fracture apertures regardless of fracture trace length. With large values of differential stress ratios, the overall permeability of the DFN models is controlled by a combination of highly conductive larger fractures and fractures with shear slipping and dilation. With increasing differential stress ratios (K=1,3,4 and 5) the REV of a fractured rock may exist at much larger model sizes comparing with the model without stress (K=0).
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| 7. |
- Baghbanan, Alireza, et al.
(författare)
-
Stress effects on permeability in fractured rock mass with correlated fracture length and aperture
- 2008
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Ingår i: International Journal of Rock Mechanics And Mining Sciences. - : Elsevier BV. - 1365-1609 .- 1873-4545. ; 45:8, s. 1320-1334
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Tidskriftsartikel (refereegranskat)abstract
- The effect of stress on permeability and fluid flow patterns in fractured rock masses is studied when distributed fracture aperture is correlated with fracture trace length, using a discrete element method (DEM). The basic assumptions are that the rock matrix is impermeable and linearly elastic, and that the fluid flows only in fractures. A new nonlinear algorithm is developed for prediction of normal stress-normal displacement behavior of fractures based on the Bandis model and the correlation between aperture and length. The results show that when small stress ratios (K = horizontal/vertical stress) are applied at the model boundaries, the overall permeability of the fracture network is generally decreased. However, contribution from a few large fractures of higher hydraulic conductivity prevents drastic reduction of the overall permeability, compared with models that assume uniform fracture apertures. With large values of the stress ratio, both the overall permeability and flow patterns are controlled by a combination of highly conductive larger fractures and fractures with shear slipping and dilation, with much increased overall permeability and shear-induced flow channeling. With increasing stress ratios, it becomes more and more difficult to establish an equivalent permeability tensor and representative elementary volume (REV) of a fractured rock, compared with the unstressed model. These results show significant difference between correlated and non-correlated aperture and fracture length distributions, and highlight more significant scale and stress dependence of hydro-mechanical behavior of fractures rocks when geometric parameters of rock fractures are correlated.
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| 8. |
- Birkholzer, Jens T., et al.
(författare)
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25 years of DECOVALEX - Scientific advances and lessons learned from an international research collaboration in coupled subsurface processes
- 2019
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Ingår i: International Journal of Rock Mechanics And Mining Sciences. - : PERGAMON-ELSEVIER SCIENCE LTD. - 1365-1609 .- 1873-4545. ; 122
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Forskningsöversikt (refereegranskat)abstract
- This paper provides an overview of an international research collaboration for advancing the understanding and modeling of coupled thermo-hydro-mechanical-chemical (THMC) processes in geological systems. The creation of the international DECOVALEX Project, now running for over 25 years, was initially motivated by the recognition that prediction of these coupled effects is an essential part of the performance and safety assessment of geologic disposal systems for radioactive waste and spent nuclear fuel. Later it was realized that these processes also play a critical role in other subsurface engineering activities, such as storage of CO2, exploration of enhanced geothermal systems, and unconventional oil and gas production through hydraulic fracturing. Research teams from radioactive waste management organizations, national research institutes, regulatory agencies, universities, as well as industry and consulting groups have participated in the DECOVALEX Project, providing a wide range of perspectives and solutions to these complex problems. Analysis and comparative modeling of state-of-the-art field and laboratory experiments has been at the core of the collaborative work, with an increasing focus on characterizing uncertainty and blind prediction of experimental results. Over these 25 years, many of the major advances in this field of research have been made through DECOVALEX, as evidenced by three books, seven journal special issues, and a good number of seminal papers that have emerged from the DECOVALEX modeling work. Examples of specific research advances will be presented in this paper to illustrate the significant impact of DECOVALEX on the current state-of-the-art of understanding and modeling coupled THMC processes. These examples range from the modeling of large-scale in situ heater tests representing mock-ups of nuclear waste disposal tunnels, to studies of fluid flow and chemical-mechanical coupling in heterogeneous fractures, and to the numerical analysis of controlled-injection meso-scale fault slip experiments.
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| 9. |
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| 10. |
- Borgesson, L., et al.
(författare)
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Thermo-hydro-mechanical characterisation of a bentonite-based buffer material by laboratory tests and numerical back analyses
- 2001
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Ingår i: International Journal of Rock Mechanics And Mining Sciences. - 1365-1609 .- 1873-4545. ; 38:1, s. 95-104
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents some laboratory tests performed on the bentonite used as buffer material in the engineered barrier experiment in Kamaishi mine in Japan and a collective effort of four research groups to characterise the coupled thermo-hydro-mechanical behaviour of the bentonite by comparing numerical calculations with the laboratory test results. Each research group used finite element programs with constitutive models capable to simulate both liquid and vapour flux of water, heat transfer, volume change, swelling pressure and mechanical deformation. Numerical calibrations were performed against results obtained from three types of laboratory tests: water infiltration tests, thermal gradient tests and swelling pressure tests. Parameter values, which could not be directly measured in laboratory tests, were obtained with these calculations.
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| 11. |
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| 12. |
- Bäckström, Ann, et al.
(författare)
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Numerical modelling of uniaxial compressive failure of granite with and without saline porewater
- 2008
-
Ingår i: International Journal of Rock Mechanics And Mining Sciences. - : Elsevier BV. - 1365-1609 .- 1873-4545. ; 45:7, s. 1126-1142
-
Tidskriftsartikel (refereegranskat)abstract
- It is important for rock engineering design to be able to validate numerical simulations, i.e. to check that they adequately represent the rock reality. In this paper, the capability and validity of four numerical models is assessed through the simulation of an apparently simple case: the complete process of microstructural breakdown during the uniaxial compressive failure of intact crystalline rock. In addition to comparing the capabilities of the four models, the results generated by each model were compared with the experimentally determined complete stress-strain curves for the Swedish Avro granite for different porewater conditions. In this way, it has been possible to audit the models' adequacy for this particular simulation task. It was found that although the models had common features, they were each idiosyncratically different and required considerable expertise to match the actual stress-strain curves (which did not monotonically increase in axial strain)-indicating that, for more complex simulations, both adequate modelling and appropriate validation are not going to be an easy task. The work was conducted within the framework of the international 2004-2007 DEmonstration of COupled models and their VALidation against EXperiments with emphasis on Thermo Hydro Mechanic and Chemical aspects (DECOVALEX-THMC) phase on coupled modelling extended to include chemical effects and with application to the excavation damaged zone (EDZ) in crystalline rock.
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| 13. |
- Chen, Y., et al.
(författare)
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A permeability evolution model for crystalline rocks subjected to coupled thermo-hydro-mechanical loading
- 2013
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Ingår i: Chinese Journal of Rock Mechanics and Engineering. - 1000-6915. ; 32:11, s. 2185-2195
-
Tidskriftsartikel (refereegranskat)abstract
- An anisotropic damage model was established for fluid-saturated crystalline rocks of low permeability in coupled thermo-hydro-mechanical (THM) loading conditions by using the micromechanical approach in the framework of thermodynamics. The proposed damage model accounts for the impacts of some important micromechanisms, such as the interstitial water pressure, normal stiffness recovery induced by compressed microcracks and sliding and shear dilatancy of closed microcracks, on the macromechanical properties of rocks under non-isothermal condition. On this basis, using various homogenization approaches, estimates were presented for the variations in effective permeability of cracked rocks induced by anisotropic damage propagation. The predictive limitations associated with the lower bound estimates for the effective permeability of damaged rocks were discussed; and a rigorous upper bound estimate was then presented to account for the influence of some important microstructural features, such as the connectivity and persistence of microcrack system, on the permeability variation. Existing laboratory tests on granite samples for damage-induced variation in permeability in triaxial condition and for uniaxial mechanical response after high-temperature thermal treatment, together with the in-situ measurements of excavation-induced damage zone and permeability variation in the surrounding rock of the TSX tunnel, were used to validate the proposed models.
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| 14. |
- Chen, Yifeng, et al.
(författare)
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Experimental characterization and micromechanical modeling of damage-induced permeability variation in Beishan granite
- 2014
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Ingår i: International Journal of Rock Mechanics And Mining Sciences. - : Elsevier BV. - 1365-1609 .- 1873-4545. ; 71, s. 64-76
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Tidskriftsartikel (refereegranskat)abstract
- Triaxial compression tests with measurements of permeability were performed on core granite samples taken at 450-550 m depth from the Beishan area in Gansu Province, a potential site for China's high-level radioactive waste (HLW) disposal. Corresponding to the distinct features in the stress-strain behaviors, the permeability of the Beishan granite was found to evolve with a clear permeability decrease in the initial microcrack closure region, a constant permeability value in the elastic region and a dramatic permeability increase in the crack growth region. The permeability increases by up to and over two orders of magnitude as deviatoric stress increases up to sample failure; but at a given deviatoric stress, the permeability reduces remarkably with the increase of confining pressure. An empirical upper bound permeability model was presented by relating the mechanisms involved in the microstructure alteration to the permeability change, and the experimental results were well simulated by the proposed model. Combined with field geological characterization and numerical simulation, the implications of the experimental results for China's HLW disposal were discussed.
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| 15. |
- Chen, Y.F, et al.
(författare)
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Numerical simulation of coupled thermal elastic behaviors for hard rock pillar in Äspö Pillar Stability Experiment, Sweden
- 2010
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Ingår i: Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering. - 1000-4548. ; 32:8, s. 1200-1206
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Tidskriftsartikel (refereegranskat)abstract
- The goal of the Äspö Pillar Stability Experiment performed in Äspö Hard Rock Laboratory, Sweden is to investigate the mechanical response and progressive failure process of ahard rock pillar during excavation and heating. Numerical simulation of the thermalelastic behaviors for the pillar is one of the three tasks of the DECOVALEX-2011 project. The evolutions of stress, deformation and temperature of the pillar are modeled by using a coupled thermal elasticity model. The research results demonstrate that the thermalelasticity model is suitable for describing the coupled thermal mechanical behaviors of the pillar during excavation and heating. The stress redistribution and temperature evolution processes of the pillar are largely modeled, and the failure process and its propagation are qualitatively analyzed. The major limitations of the thermal elasticity model are its absence of the multiphase flow and progressive failure processes. The model developed and the modeling experiences accumulated in this study may be helpful for the stability and safety assessment of the hard granite host rock in China's Beishan preselected area for high-level radioactive waste disposal.
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| 16. |
- Chen, Yifeng, et al.
(författare)
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Micromechanical Modeling of Anisotropic Damage-Induced Permeability Variation in Crystalline Rocks
- 2014
-
Ingår i: Rock Mechanics and Rock Engineering. - : Springer Science and Business Media LLC. - 0723-2632 .- 1434-453X. ; 47:5, s. 1775-1791
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a study on the initiation and progress of anisotropic damage and its impact on the permeability variation of crystalline rocks of low porosity. This work was based on an existing micromechanical model considering the frictional sliding and dilatancy behaviors of microcracks and the recovery of degraded stiffness when the microcracks are closed. By virtue of an analytical ellipsoidal inclusion solution, lower bound estimates were formulated through a rigorous homogenization procedure for the damage-induced effective permeability of the microcracks-matrix system, and their predictive limitations were discussed with superconducting penny-shaped microcracks, in which the greatest lower bounds were obtained for each homogenization scheme. On this basis, an empirical upper bound estimation model was suggested to account for the influences of anisotropic damage growth, connectivity, frictional sliding, dilatancy, and normal stiffness recovery of closed microcracks, as well as tensile stress-induced microcrack opening on the permeability variation, with a small number of material parameters. The developed model was calibrated and validated by a series of existing laboratory triaxial compression tests with permeability measurements on crystalline rocks, and applied for characterizing the excavation-induced damage zone and permeability variation in the surrounding granitic rock of the TSX tunnel at the Atomic Energy of Canada Limited's (AECL) Underground Research Laboratory (URL) in Canada, with an acceptable agreement between the predicted and measured data.
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| 17. |
- Chen, Yifeng, et al.
(författare)
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Modeling coupled THM processes of geological porous media with multiphase flow : Theory and validation against laboratory and field scale experiments
- 2009
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Ingår i: Computers and geotechnics. - : Elsevier BV. - 0266-352X .- 1873-7633. ; 36:8, s. 1308-1329
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Tidskriftsartikel (refereegranskat)abstract
- A FEM model for analysis of fully coupled multiphase flow, thermal transport and stress/deformation in geological porous media was developed based on the momentum, mass and energy conservation laws of the continuum mechanics and the averaging approach of the mixture theory over a three phase (solid-liquid-gas) system. Six processes (i.e. stress-strain, water flow, gas flow, vapor flow, heat transport and porosity evolution processes) and their coupling effects are considered, which not only makes the problem well-defined, but renders the governing PDEs closed, complete. compact and compatible. Displacements, pore water pressure, pore gas pressure, pore vapor pressure, temperature and porosity are selected as basic unknowns. The physical phenomena such as phase transition, gas solubility in liquid, thermo-osmosis, moisture transfer and moisture swelling are modeled. As a result, the relative humidity and other related variables in porous media can be evaluated on a sounder physical basis. A three dimensional computer code, THYME3D, was developed, with eight degrees of freedom at each node. The laboratory CEA Mock-up test and the field scale FEBEX benchmark test on bentonite performance assessment for underground nuclear waste repositories were used to validate the numerical model and the software. The coupled THM behaviors of the bentonite barriers were satisfactorily simulated, and the effects and impacts of the governing equations, constitutive relations and property parameters on the coupled THM processes were understood in terms of more straightforward interpretation of physical processes at microscopic scale of the porous media. The work developed enables further in-depth research on fully coupled THM or THMC processes in porous media.
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| 18. |
- Chen, Y., et al.
(författare)
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Numerical model for fully coupled THM processes with multiphase flow and code validation
- 2009
-
Ingår i: Chinese Journal of Rock Mechanics and Engineering. - 1000-6915. ; 28:4, s. 649-665
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Tidskriftsartikel (refereegranskat)abstract
- A numerical model for fully coupled THM processes with multiphase flow in porous media was developed based on the momentum, mass and energy conservation laws of the continuum mechanics and the averaging approach of the mixture theory over a solid-liquid-gas three-phase system. To characterize multiphase THM coupling and to make the governing equations closed, complete and compatible, six processes and their coupling effects were considered, including stress-strain, water flow, gas flow, vapor flow, heat transport and porosity evolution processes. The physical phenomena such as phase transition, gas solubility in liquid, thermo-osmosis, moisture transfer and moisture swelling were modeled. As a result, the relative humidity of pore gas was defined on a sounder physical basis, avoiding the traditional definition as a negative exponential function of suction and absolute temperature. By selecting displacements, pore water pressure, pore gas pressure, pore vapor pressure, temperature and porosity as basic unknown variables, a finite element formulation was then established, and a three-dimensional computer code, THYME3D, was developed, with each node of 8 degrees of freedom. The bentonite THM Mock-up experiments performed by CEA were employed to validate the mathematical model and the software. The main coupling mechanisms involved in the experiments were satisfactorily simulated in the validation, and the effects of the governing equations, the constitutive relations and the parameters on the coupled THM processes were understood. The work developed enabled further in-depth research on fully coupled THM or THMC processes in porous media.
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| 19. |
- Chijimatsu, M., et al.
(författare)
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Building Confidence in the Mathematical Models by Calibration With A T-H-M Field Experiment
- 2004
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Ingår i: Coupled Thermo-Hydro-Mechanical-Chemical Processes in Geo-Systems — Fundamentals, Modelling, Experiments and Applications. - : Elsevier. ; , s. 193-198
-
Bokkapitel (refereegranskat)abstract
- Geological disposal of nuclear fuel wastes relies on the concept of multiple barrier systems. In order to predict the performance of these barriers, mathematical models have been developed, verified and validated against analytical solutions, laboratory tests and field experiments within the international DECOVALEX project. These models in general consider the full coupling of thermal (T), hydrological (H) and mechanical (M) processes that would prevail in the geological media around the repository. This paper shows the process of building confidence in the mathematical models by calibration with a reference T-H-M experiment with realistic rock mass conditions and bentonite properties and measured outputs of thermal, hydraulic and mechanical variables.
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| 20. |
- Chijimatsu, Masakazu, et al.
(författare)
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Model development and calibration for the coupled thermal, hydraulic and mechanical phenomena of the bentonite
- 2009
-
Ingår i: Environmental Geology. - : Springer Science and Business Media LLC. - 0943-0105 .- 1432-0495. ; 57:6, s. 1255-1261
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Tidskriftsartikel (refereegranskat)abstract
- In the international DECOVALEX-THMC project, five research teams study the influence of thermal-hydro-mechanical (THM) coupling on the safety of a hypothetical geological repository for spent fuel. In order to improve the analyses, the teams calibrated their bentonite models with results from laboratory experiments, including swelling pressure tests, water uptake tests, thermally gradient tests, and the CEA mock-up THM experiment. This paper describes the mathematical models used by the teams, and compares the results of their calibrations with the experimental data.
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| 21. |
- Chijimatsu, M., et al.
(författare)
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Numerical study of the THM effects on the near-field safety of a hypothetical nuclear waste repository - BMT1 of the DECOVALEX III project. Part 1 : Conceptualization and characterization of the problems and summary of results
- 2005
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Ingår i: International Journal of Rock Mechanics And Mining Sciences. - : Elsevier BV. - 1365-1609 .- 1873-4545. ; 42:5-6, s. 720-730
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Tidskriftsartikel (refereegranskat)abstract
- Geological disposal of the spent nuclear fuel often uses the concept of multiple barrier systems. In order to predict the performance of these barriers, mathematical models have been developed, verified and validated against analytical solutions, laboratory tests and field experiments within the international DECOVALEX III project. These models in general consider the full coupling of thermal (T), hydraulic (H) and mechanical (M) processes that would prevail in the geological media around the repository. For Bench Mark Test no. 1 (BMTI) of the DECOVALEX III project, seven multinational research teams studied the implications of coupled THM processes on the safety of a hypothetical nuclear waste repository at the near-field and are presented in three accompanying papers in this issue. This paper is the first of the three companion papers, which provides the conceptualization and characterization of the BMT1 as well as some general conclusions based on the findings of the numerical studies. It also shows the process of building confidence in the mathematical models by calibration with a reference T-H-M experiment with realistic rock mass conditions and bentonite properties and measured outputs of thermal, hydraulic and mechanical variables.
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| 22. |
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| 23. |
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| 24. |
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| 25. |
- Feng, Q., et al.
(författare)
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A new method for in-situ non-contact roughness measurement of large rock fracture surfaces
- 2003
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Ingår i: Rock Mechanics and Rock Engineering. - : Springer Science and Business Media LLC. - 0723-2632 .- 1434-453X. ; 36:1, s. 3-25
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a new method for in-situ non-contact measurements of fracture roughness by using a total station (TS). The TS is a non-reflector geodetic instrument usually used for measuring control points in surveying and mapping. By using a special-developed program, the TS can be used as a point-sensor laser scanner to scan a defined area of the fracture surface automatically, in field or in laboratory, at a distance away from the target surface. A large fracture surface can be automatically scanned with a constant interval of the sampling points, both within a defined area or along a cross-section of the exposed rock face. To quantify fracture roughness at different scales and obtain different densities of the scanned points, the point interval can be selected with the minimum interval of I rum. A local Cartesian co-ordinate system needs to be established first by the TS in front of the target rock face to define the true North or link the measurements to a known spatial co-ordinate system for both quantitative and spatial analysis of fracture roughness. To validate the method, fracture roughness data recorded with a non-reflector TS was compared with the data captured by a high-accuracy 3D-laser scanner. Results of this study revealed that both primary roughness and waviness of fracture surfaces can be quantified by the TS in the same accuracy level as that of the high accuracy laser scanner. Roughness of a natural fracture surface can be sampled without physical contact in a maximum distance of tens of meters from the rock faces.
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| 26. |
- Feng, Q., et al.
(författare)
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Measuring fracture orientation at exposed rock faces by using a non-reflector total station
- 2001
-
Ingår i: Engineering Geology. - 0013-7952 .- 1872-6917. ; 59:1-2, s. 133-146
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Tidskriftsartikel (refereegranskat)abstract
- Measurements of fracture orientation are usually taken by using a compass-inclinometer device on exposed rock faces. The drawbacks when using this method is that it is time-consuming if many fractures are measured and that measurement might be impossible if the rock face cannot be safely reached physically. To improve field mapping of rock fractures, a method for applying a non-reflector total station to measuring fracture orientation is presented in this paper. A non-reflector total station is a geodetic device that captures three-dimensional co-ordinates of target points without using a reflector. Therefore, physical touching the rock surfaces is no longer required. To determine a fracture orientation, co-ordinates of a set of points on the exposed fracture surface are captured at a distance from the rock face. The best-fit plane of the exposed fracture surface is defined by the co-ordinates of the target points, and the orientation (e.g. dip angle and dip direction) of the fracture surface is determined as that of its best-fit plane. This paper presents the technical procedure and a portable system designed for the field mapping of fracture orientation. Results of a case study performed at an exposed rock face are also included.
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| 27. |
- Feng, X. -T, et al.
(författare)
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Research and application on coupled t-h-m-c processes of geological media in china - a review
- 2004
-
Ingår i: Coupled Thermo-Hydro-Mechanical-Chemical Processes in Geo-Systems — Fundamentals, Modelling, Experiments and Applications. - : Elsevier. ; , s. 37-48
-
Bokkapitel (refereegranskat)abstract
- Theoretical models of coupled T-H-M-C processes of geological media and the associated numerical solutions have become an attractive research focus in geomechanics and related fields in China. This paper provides a systematic overview of the past progress in the fundamental studies of the coupled THM models and numerical methods, and their applications in the fields of oil/gas reservoir, coal mining, and water resources engineering works. The key areas of weakness in research in this field are also outlined and possible directions for the future development are discussed.
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| 28. |
- Henkel, Herbert, et al.
(författare)
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A deep rock laboratory in the Dellen impact crater
- 2010
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Ingår i: GFF. - : Informa UK Limited. - 1103-5897 .- 2000-0863. ; 132:1, s. 45-54
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Tidskriftsartikel (refereegranskat)abstract
- The Deep Rock Lab is a platform to establish a comprehensive subsurface bedrock characterization approach, by integrating site characterization techniques applied from different disciplines of geo-mechanics, geochemistry, hydrogeology, structural geology, lithology and geophysics, with consideration of the effects of coupled geological processes of importance for the understanding of groundwater renewal, continental shield deformations, engineering issues related to geological disposal of nuclear waste and CO2, and geothermal energy retrieval in crystalline rocks. The approach will focus on the physics and chemistry of crystalline rocks and groundwater with down-the-hole measurements of relevant variables, using and developing more efficient geo-scientific site investigation techniques for deep boreholes at a chosen site, and develop more advanced down-the-hole measurements and numerical modelling methods with more advanced inversion algorithms to help integrate data interpretations and object representations. The goal is to develop this platform into a long-term research facility that can be readily used by the scientific community for both subsurface fundamental and engineering-oriented research. Such a platform will be especially important for the education of PhD students for generations to come. The integrated drilling and research facility is suggested to be located at the Dellen site. This site has an impact crater with a large range of expected physical property changes with depth, complex and multiple thermal processes that have affected the bedrock, a favorable infrastructure and local supporting activities, and a large body of existing geo-scientific data.
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| 29. |
- Hudson, John A., et al.
(författare)
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Characterising and modelling the excavation damaged zone in crystalline rock in the context of radioactive waste disposal
- 2009
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Ingår i: Environmental Geology. - : Springer Science and Business Media LLC. - 0943-0105 .- 1432-0495. ; 57:6, s. 1275-1297
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes current knowledge about the nature of and potential for thermo-hydro-mechanical-chemical modelling of the excavation damaged zone (EDZ) around the excavations for an underground radioactive waste repository. In the first part of the paper, the disturbances associated with excavation are explained, together with reviews of Workshops that have been held on the subject. In the second part of the paper, the results of a DECOVALEX [DEmonstration of COupled models and their VALidation against EXperiment: research funded by an international consortium of radioactive waste regulators and implementers (http://www.decovalex.com)] research programme on modelling the EDZ are presented. Four research teams used four different models to simulate the complete stress-strain curve for Avro granite from the Swedish A"spo Hard Rock Laboratory. Subsequent research extended the work to computer simulation of the evolution of the repository using a 'wall-block model' and a 'near-field model'. This included assessing the evolution of stress, failure and permeability and time-dependent effects during repository evolution. As discussed, all the computer models are well suited to sensitivity studies for evaluating the influence of their respective supporting parameters on the complete stress-strain curve for rock and for modelling the EDZ.
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| 30. |
- Hudson, J. A., et al.
(författare)
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Coupled T-H-M issues relating to radioactive waste repository design and performance
- 2001
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Ingår i: International Journal of Rock Mechanics And Mining Sciences. - 1365-1609 .- 1873-4545. ; 38:1, s. 143-161
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Tidskriftsartikel (refereegranskat)abstract
- In this paper. coupled thermo-hydro-mechanical (THM) issues relating to nuclear waste repository design and performance are reviewed. Concise statements. that were developed from DECOVALEX discussions, on the current state-of-knowledge are presented. Section 1 describes the THM background and the interface with performance assessment (PA). The role of THM issues in the overall repository design context is amplified in Section 2, which includes a review of the processes in terms of repository excavation. operation and post-closure stages. It is important to understand the overall context, the detailed THM issues, the associated modelling and how these issues will be resolved in the wider framework. Also, because uncoupled and coupled numerical codes have been used fur this subject, there is discussion in Section 3 on the nature of the codes and how the content of the codes can be audited. To what extent does a particular code capture the essence of the problem in hand? Consideration is also given to the associated question of code selection and the future of numerical codes. The state-of-knowledge statements are presented in Section 4 under 11 headings which follow the repository design sequence. The overview conclusion is that A predictive THM capability is required to support repository design because precedent practice information is insufficient. Many aspects of THM processes and modelling are now well understood and there is a variety of numerical codes available to provide solutions for different host rock and repository conditions. However, modelling all the THM mechanisms in space and time is extremely complex and simplifications will have to be made - if only because it is not possible to obtain all the necessary detailed supporting information. Therefor, an important step is to clarify the THM modelling requirement within the PA context. This will help to indicate the complexity of THM modelling required and hence the models. mechanisms, type of computing, supporting data, laboratory and in situ testing, etc, required. An associated transparent and open audit trail should be developed. We also include comments from reviewers and highlight four outstanding issues which are currently being studied in the DECOVALEX III programme.
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| 31. |
- Hudson, J. A., et al.
(författare)
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Coupled THMC modeling for safety assessment of geological disposal of radioactive wastes : The DECOVALEX project (1992-2015)
- 2017
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Ingår i: Rock Mechanics and Engineering Volume 3: Analysis, Modeling and Design. - : CRC Press. - 9781317481942 - 9781138027619 ; , s. 3-44
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- This Chapter describes a long-term research effort (1992 to the present) on coupled THMC processes in geological systems in the context of the safe geological disposal of radioactive wastes: the DECOVALEX project (DEvelopment of COupled models and their VAlidation through EXperiments). This project is a unique international co-operative research project which was initiated in 1991, officially started in 1992, has continued through a number of phases without interruption since then and is still continuing in the time of preparing this chapter by the authors. The overall objective of this research has been the development, validation and application of numerical modeling methods and techniques for the performance and safety assessments of geological disposal of radioactive waste (GDRW) in underground repositories. The cooperation has been financed by national waste management organizations, regulatory bodies and national research institutes and individual universities in Canada, China, Czech Republic, European Commission, Finland, France, Germany, Republic of Korea, Spain, Japan, Sweden, UK and USA.Over the period of 23 years, the project has made impressive advanced researches in the field of coupled THMC (Thermo- Hydro-Mechanical-Chemical) processes in geological systems, especially in fractured crystalline and sedimentary rocks and buffer/backfill materials, through integrated numerical modeling and laboratory and field experiments. The experiments cover scales ranging from laboratory-sized samples to in situ experiments in underground research laboratories (URLs) in different host rocks in different countries. The work has resulted in an impressive number ofmajor developments, as reported in scientific publications and helped to educate and train younger generations of researchers in this field. This Chapter presents the goals, structure, contents and approaches of the project, as well as achievements and lessons learned during this long-term project, at both the fundamental and application levels.
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| 32. |
- Hudson, J. A., et al.
(författare)
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Demonstration of coupled models and their validation against experiment : The current phase DECOVALEX 2015
- 2013
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Ingår i: Rock Characterisation, Modelling and Engineering Design Methods - Proceedings of the 3rd ISRM SINOROCK 2013 Symposium. - : Taylor & Francis Group. ; , s. 391-396
-
Konferensbidrag (refereegranskat)abstract
- The DECOVALEX Project (DEmonstration of COupled models and their VALidation against EXperiment) has been operating since 1992 with the objective of developing thermo-hydro-mechanical coupled computer modelling in order to provide the necessary support for the design of underground radioactive waste repositories. The Project consists of Benchmark Tests which are synthetic models for comparison of different research teams' computer modelling results (verification), and Test Cases which are simulations of actual physical cases to establish whether the modelling does in fact represent the rock reality (validation). An international consortium of Funding Organisations supports the DECOVALEX work, currently the following ten Funding Organisations: BGR/UFZ (Germany), CAS (China), DOE (USA), ENSI (Switzerland), IRSN (France), JAEA (Japan), KAERI (Korea), NDA (UK), NRC (USA) and RAWRA (Czech Republic). In this paper, we explain the 2011-2015 DECOVALEX modelling tasks which cover the range of argillaceous, sedimentary and crystalline rocks.
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| 33. |
- Jing, Lanru
(författare)
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A review of techniques, advances and outstanding issues in numerical modelling for rock mechanics and rock engineering
- 2003
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Ingår i: International Journal of Rock Mechanics And Mining Sciences. - : Elsevier BV. - 1365-1609 .- 1873-4545. ; 40:3, s. 283-353
-
Forskningsöversikt (refereegranskat)abstract
- The purpose of this review paper is to present the techniques. advances. problems and likely future developments in numerical modelling for rock mechanics. Such modelling is essential for studying the fundamental processes occurring in rocks and for rock engineering design. The review begins by explaining the special nature of rock masses and the consequential difficulties when attempting to model their inherent characteristics of discontinuousness. anisotropy, inhomogencity and inelasticity. The rock engineering design backdrop to the review is also presented. The different types of numerical models are outlined in Section 2. together with a discussion on how, to obtain the necessary parameters for the models. There is also discussion on the value that is obtained from the modelling. especially the enhanced understanding of those mechanisms initiated by engineering perturbations. In Section 3, the largest section. states-of-the-art and advances associated with the main methods are presented in detail. In many cases. for the model to adequately represent the rock reality. it is necessary to incorporate couplings between the thermal. hydraulic and mechanical processes. The physical processes and the equations characterizing the coupled behaviour are included in Section 4. with an illustrative example and discussion on the likely future development of coupled models. Finally. in Section 5. the advances and outstanding issues in the subject are listed and in Section 6 there are specific recommendations concerning quality control. enhancing confidence in the models, and the potential future developments.
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| 34. |
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| 35. |
- Jing, Lanru, et al.
(författare)
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An experimental study on the anisotropy and stress-dependency of the strength and deformability of rock joints
- 1992
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Ingår i: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts. - : Elsevier BV. - 0148-9062 .- 1879-2073. ; 29:6, s. 535-542
-
Tidskriftsartikel (refereegranskat)abstract
- The anisotropy and stress-dependency of the strength and deformability of rock joints were investigated experimentally through shear tests of concrete replicas of natural rock joints. 50 concrete replicas of two natural granite joints were sheared on a servo-controlled hydraulic test frame under different magnitudes of normal stress and in different shear directions. Significant anisotropy in both the friction angle and shear stiffness of concrete replicas of joints were observed and both of them change with the variation of normal stress. The rates of dilatancy and contraction of joint samples appear to be different during cyclic shear tests, depending very much on the initial conditions of sample surfaces. Empirical relations were then postulated to describe these newly found properties of joint samples and used in developing new constitutive models for rock joints
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| 36. |
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| 37. |
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| 38. |
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| 39. |
- Jing, Lanru, et al.
(författare)
-
Discrete Fracture Network (DFN) Method
- 2007
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Ingår i: Fundamentals Of Discrete Element Methods For Rock Engineering. - : Elsevier. - 9780444829375 ; , s. 365-398
-
Bokkapitel (refereegranskat)
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| 40. |
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| 41. |
- Jing, Lanru, et al.
(författare)
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Distinct element modelling of sublevel stoping
- 1991
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Ingår i: Berichte. - Rotterdam : Balkema Publishers, A.A. / Taylor & Francis The Netherlands. - 9054100125 ; , s. 741-746
-
Konferensbidrag (refereegranskat)
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| 42. |
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| 43. |
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| 44. |
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| 45. |
- Jing, Lanru, et al.
(författare)
-
Fundamentals of the hydro-mechanical behaviour of rock fractures : roughness characterization and experimental aspects
- 2004
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Ingår i: International Journal of Rock Mechanics And Mining Sciences. - : Elsevier BV. - 1365-1609 .- 1873-4545. ; 41:3, s. 383-383
-
Tidskriftsartikel (refereegranskat)abstract
- The coupled hydro-mechanical behaviour of rock fractures plays an important role in design, performance and safety assessments of rock engineering projects. However, due to the complexity in the mathematical representation of the fracture surface geometry and its effects on the stress-flow behaviour of the fractures, and the limitations in the test conditions in laboratories, significant lack of knowledge still exists in testing and modelling approaches regarding rock fractures. Based on a general review of the roughness characterization and shear-flow testing of rock fractures, this paper presents the definition of the stationarity threshold of roughness, and a combined experimental-numerical approach for simulating rock fracture testing conditions for more general fluid flow behaviour of the rock fractures. The conclusions are that fracture roughness characterization must be conducted and represented in three-dimensions and the more general fluid flow behaviour cannot be observed with conventional parallel shear-flow tests or compressionradial flow tests. Numerical simulations are needed to reveal more general behaviour of stress-flow processes of rock fractures with boundary and loading conditions that are difficult or impractical in laboratory tests.
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| 46. |
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| 47. |
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| 48. |
- Jing, Lanru, et al.
(författare)
-
Introduction
- 2007
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Ingår i: Fundamentals of Discrete Element Methods for Rock Engineering Theory and Applications. - : Elsevier. - 9780444829375 ; , s. 1-21
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 49. |
- Jing, Lanru, et al.
(författare)
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Main rock mechanics issues in geological disposal of radioactive wastes : Yanshilixue Yu Gongcheng Xuebao
- 2006
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Ingår i: Chinese Journal of Rock Mechanics and Engineering. - 1000-6915. ; 25:4, s. 833-841
-
Tidskriftsartikel (refereegranskat)abstract
- Geological disposal of radioactive wastes is a multi-disciplinary issue of importance for national interest. It stimulated many challenging scientific and technical issues, and at a higher level, presented a series of demanding requirements for a country's overall research and development programme, its implementation and engineering practice, about basic policies and legislature concerning nuclear energy, defense, waste management and environment. Rock mechanics and rock engineering are very important fields for geological disposal of radioactive wastes, and contribute significantly to the conceptual design, site investigation, engineering design and construction, operation and the long-term safety assessment of the waste repositories. It plays, therefore, a irreplaceable role in the research and development programme of geological disposal of radioactive wastes. In this paper, we first summarizes briefly the main steps about repository system, followed by the major demands for rock mechanics and rock engineering during feasibility study and site investigation, and the major international trends concerning these issues. The focus is placed on the coupled thermo-hydro-mechanical and chemical (THMC) processes and the current status of research in international communities. At the end, the progresses in research and development works in the field of radioactive waste disposal in China are presented; and possible future working directions are discussed.
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| 50. |
- Jing, Lanru, et al.
(författare)
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Numerical methods in rock mechanics
- 2002
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Ingår i: International Journal of Rock Mechanics And Mining Sciences. - 1365-1609 .- 1873-4545. ; 39:4, s. 409-427
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Forskningsöversikt (refereegranskat)abstract
- The purpose of this CivilZone review paper is to present the techniques, advances, problems and likely future development directions in numerical modelling for rock mechanics and rock engineering. Such modelling is essential for Studying the fundamental processes occurring in rock,, for assessing the anticipated and actual performance of structures built on and in rock masses, and C hence for Supporting rock engineering design. We begin by providing the rock engineering design backdrop to the review in Section 1. The states-of-the-art of different types of numerical methods are outlined in Section 2, with focus on representations of fractures in the rock mass. In Section 3, the numerical methods for incorporating couplings between the thermal, hydraulic and mechanical processes are described. In Section 4, inverse solution techniques are summarized. Finally, in Section 5, we list the issues of special difficulty and importance in the subject. In the reference Est, 'significant' references are asterisked and 'very significant' references are doubly asterisked.
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