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  • 1.
    Al-Ajmi, Adel M.
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Zimmerman, Robert W.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Stability analysis of vertical boreholes using the Mogi-Coulomb failure criterion2006In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 43, no 8, p. 1200-1211Article in journal (Refereed)
    Abstract [en]

    A main aspect of wellbore stability analysis is the selection of an appropriate rock failure criterion. The most commonly used criterion for brittle failure of rocks is the Mohr-Coulomb criterion. This criterion involves only the maximum and minimum principal stresses, a, and sigma(3), and therefore assumes that the intermediate stress 92 has no influence on rock strength. As the Mohr-Coulomb criterion ignores the strengthening effect of the intermediate stress, it is expected to be too conservative in estimating the critical mud weight required to maintain wellbore stability. Recently, Al-Ajmi and Zimmerman [Relationship between the parameters of the Mogi and Coulomb failure criterion. Int J Rock Mech Min Sci 2005;42(3):431-39.] developed the Mogi-Coulomb failure criterion, and showed that it is reasonably accurate in modelling polyaxial failure data from a variety of rocks. We then develop a model for the stability of vertical boreholes, using linear elasticity theory to calculate the stresses, and the fully-polyaxial Mogi-Coulomb criterion to predict failure. Our model leads to easily computed expressions for the critical mud weight required to maintain wellbore stability.

  • 2. Al-ajmi, A.M
    et al.
    Zimmerman, Robert W
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Relation between the Mogi and the Coulomb failure criteria2005In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 42, no 3, p. 431-439Article in journal (Refereed)
    Abstract [en]

    We have shown that linear Mogi criterion does a good job in representing rock failureunder polyaxial stress states. When σ2 = σ3 the linear version of Mogi's triaxial failurecriterion reduces exactly to the Coulomb criterion. Hence, the linear Mogi criterion can be thought of as a natural extension of the Coulomb criterion into three dimensions (i.e., polyaxial stress space). As Mohr's extension of the Coulomb criterion into three dimensions is often referred to as the Mohr-Coulomb criterion, we propose that the linear version of the Mogi criterion be known as the "Mogi-Coulomb" failure criterion. The classical Coulomb failure criterion can therefore be thought of as a special case, which applies only when σ2 = σ3 of the more general linear Mogi failure criterion. Furthermore, we found that the numerical values of the parameters that appear in the Mogi-Coulombcriterion can be estimated from conventional triaxial test data. Thus, this polyaxial failurecriterion can be applied even in the absence of polyaxial (true triaxial) data. This offers a great advantage, as most laboratories are equipped to conduct only traditional σ2 = σ3tests. Finally, we showed that if the linear form of the Mogi criterion is used, the parameters that appear in it can be unambiguously related to the traditional parameters appearing in the Coulomb failure law. The lack of such a relationship for the parameters appearing in the power-law Mogi criterion has been cited in [8] as a major drawback to the use of that model. 

  • 3. Andersson, J. Christer
    et al.
    Martin, C. Derek
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    The Aspo Pillar Stability Experiment: Part II-Rock mass response to coupled excavation-induced and thermal-induced stresses2009In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 46, no 5, p. 879-895Article in journal (Refereed)
    Abstract [en]

    A 1-m-thick pillar was subject to coupled excavation- and thermal-induced stresses to induce brittle rock mass yielding. The yielding strength of the heterogeneous and fractured rock mass consisting of Aspo diorite was evaluated at eighteen discrete locations using data from the displacement, acoustic emission, and thermal monitoring systems. The average rock mass yielding strength was determined to be 0.59 of the uniaxial compressive strength. The onset of dilation in uniaxial laboratory tests, determined from strain gauge data, was found to occur at approximately 0.45 of the uniaxial compressive strength. It was shown that that the onset of acoustic emission events in situ also occurred when the tangential stress exceeded 0.43 of the uniaxial compressive strength. For sites with absence of in situ data it is recommended that this lower-bound value determined from laboratory data may be used for assessing the in situ rock mass yielding strength. Visual observation and displacement monitoring showed that extent of rock mass yielding is sensitive to small changes in the tangential stress magnitudes. It was determined using three-dimensional modelling that changes in the tangential stress magnitude of approximately 1 MPa was sufficient to cause yielding of the pillar to propagate in what appeared to be intact rock. Observations suggest that without this small stress change yielding of the rock mass would not occur. In other words, there appeared to be a well defined boundary, and if the stresses reached this boundary yielding was observed. However, if stresses were only slightly below this boundary yielding or time-dependant processes were not observed over the monitoring period used in the experiment.

  • 4.
    Ask, Daniel
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Measurement-related uncertainties in overcoring data at the Aspo HRL, Sweden. Part 2: Biaxial tests of CSIRO HI overcore samples2006In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 43, no 1, p. 127-138Article in journal (Refereed)
    Abstract [en]

    This paper is the second dealing with measurement-related uncertainties of overcoring data undertaken at the Aspo Hard Rock Laboratory and focuses on the biaxial test data from CSIRO HI overcore samples. The first paper dealt with measurement-related uncertainties in connection with the overcoring phase [1]. The uncertainties identified in connection to biaxial tests of CSIRO HI overcore samples include too large applied pressures and poor sampling frequency. At the Aspo HRL, the results yield that most overcore samples fractured during biaxial testing, meaning that a significant part, 56%, of available strain gauge combinations were removed from calculations of the elastic parameters. Remaining strain gauge combinations indicate average values of 62 +/- 5 GPa for Young's modulus and 0.25 +/- 0.01 for Poisson's ratio, which are considerably lower than previously published values [2-5], and are in good agreement with results from biaxial tests on Borre Probe overcore samples [6-10]. The stress calculations were obtained from re-analyzed elastic parameters and strains, and show primarily a reduction in stress magnitudes. Overall, the stress field obtained with different stress measurement methods and its variation with depth is now quite well resolved. The overcoring data suggest that the principal stresses are inclined with a vertical component dipping about 65 degrees from the horizontal over the investigated rock volume (140-420 m depth). This is interpreted as a result of influence from the sub-vertical NE-2 Fracture Zone that divides the stress data into two stress domains [11], although it may also be an artefact because the sigma(2)- and sigma(3)-magnitudes are of the same order of magnitude.

  • 5.
    Ask, Daniel
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    New developments in the Integrated Stress Determination Method and their application to rock stress data at the Aspo HRL, Sweden2006In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 43, no 1, p. 107-126Article in journal (Refereed)
    Abstract [en]

    The Integrated Stress Determination Method (ISDM) is a powerful tool for estimating the regional stress tensor from in-situ measurements of local stress tensors using a wide variety of stress measuring techniques. This study presents new developments of the ISDM: The stress field may be described with up to 12 model parameters; and is applicable to data from CSIR- and CSIRO HI-type of overcoring devices, hydraulic fracturing, hydraulic tests of pre-existing fractures (HTPF), as well as to combined data sets. Furthermore, in combined data sets, the hydraulic fracturing and/or HTPF data may be used to constrain the average elastic parameters, Young's modulus and Poisson's ratio. The new ISDM developments were applied to the extensive and recently re-analysed rock stress data at the Aspo Hard Rock Laboratory. The results reveal a good fit of the re-analysed data. Overall, the re-analysis indicates that the stress field at Aspo HRL is relatively well constrained and consistent with depth. The NE-2 Fracture Zone influences the stresses, and dividing the regional stress field into a NW and a SE stress domain. When the hydraulic fracturing data were used to constrain the average elastic parameters, Young's modulus, E, and Poisson's ratio, v, quite similar results were obtained (E = 50.8 GPa and v = 0.33) compared with results from biaxial tests of overcore samples (E = 61.6 MPa and v = 0.26).

  • 6.
    Backers, Tobias
    et al.
    GeoForschungsZentrum Potsdam.
    Dresen, Georg
    GeoForschungsZentrum Potsdam.
    Rybacki, Erik
    GeoForschungsZentrum Potsdam.
    Stephansson, Ove
    GeoForschungsZentrum Potsdam.
    New data on Mode II fracture toughness of rock from the punch through shear test2004In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 41, no 1, p. 2-7Article in journal (Refereed)
    Abstract [en]

    The Punch-Through Shear (PTS) test was introduced as a method to determine the ModeII fracture toughness of rock material (Backers et al., 2002). Its unique feature is the ability to apply a confining pressure independent of the Mode II (shear) loading. This contribution reports new data on Mode II fracture toughness', KIIC, dependency on confining pressure, loading rate, sample size, and cyclic loading for six different rocktypes. Samples are subjected to different confining pressures up to 70 MPa. KIICincreases with increasing confining pressure and tends to reach a constant value at confining pressures higher than 20-35 MPa. Evidence for 'pure' Mode II fracturetoughness at high confining pressures is reported. Variation of loading rate over five orders of magnitude (10-8 - 10-3 m/s) does not change KIIC. The influence of sample size on coarser grained rocks is verified. Cyclic loading illustrates change of stiffness of the system as fracture propagation takes place. It is concluded that the PTS- test is a suitable future method for KIICtermination.

  • 7.
    Backers, Tobias
    et al.
    GeoForschungsZentrum Potsdam.
    Dresen, Georg
    GeoForschungsZentrum Potsdam.
    Rybacki, Erik
    GeoForschungsZentrum Potsdam.
    Stephansson, Ove
    GeoForschungsZentrum Potsdam.
    New data on Mode II fracture toughness of rock from the punch-through shear test2004In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 41, no 3, p. 351-352Article in journal (Refereed)
  • 8.
    Baghbanan, Alireza
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Jing, Lanru
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Effects of size and stress on deformability and strength of fractured rocks with correlated fracture aperture and length2008In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545Article in journal (Other academic)
  • 9.
    Baghbanan, Alireza
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Jing, Lanru
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Hydraulic properties of fractured rock masses with correlated fracture length and aperture2007In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 44, no 5, p. 704-719Article in journal (Refereed)
    Abstract [en]

    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.

  • 10.
    Baghbanan, Alireza
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Jing, Lanru
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Stress effects on permeability in fractured rock mass with correlated fracture length and aperture2008In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 45, no 8, p. 1320-1334Article in journal (Refereed)
    Abstract [en]

    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.

  • 11.
    Bjureland, William
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Spross, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Johansson, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Prästings, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Reliability aspects of rock tunnel design with the observational method2017In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 98, p. 102-110Article in journal (Refereed)
    Abstract [en]

    According to Eurocode 7, two accepted approaches for managing uncertainty in tunnel design are reliability based methods and the observational method. Reliability-based methods account for uncertainty by acknowledging the random variation of the input parameters; the observational method does this by verifying the expected behavior from an initial design during the course of construction. However, in the framework of the observational method, as defined in Eurocode 7, no guidance is given on the selection of suitable parameters for observation and how they can be linked to the limits of acceptable behavior and, at a sufficiently early stage, the decision for implementing contingency actions. Furthermore, no guidance is given on how to verify that the structure fulfills society's required safety level. In this paper, we present a design procedure for shotcrete-supported rock tunnels that combines reliability-based methods with the observational method. The design procedure applies a deformation-based limit state function for the shotcrete support that is based on the convergence confinement method. We suggest how the requirements in the observational method, as defined in Eurocode 7, may be satisfied for this application. In particular, we focus on the structural reliability aspects. The structural reliability of the preliminary design is assessed with Monte Carlo simulations by calculating the expected deformations of the tunnel. The appropriateness of the preliminary design is then verified by observing the actual deformations during the course of construction. The observed deformations are used to predict the future behavior of the tunnel and to update the assessed probability of unsatisfactory behavior. If the defined deformation-based alarm limit regarding the structural reliability is exceeded, predefined contingency actions are put into operation. The procedure is illustrated with a shotcrete-lined circular rock tunnel and practical aspects in satisfying the reliability requirements with the observational method are discussed.

  • 12. Borgesson, L.
    et al.
    Chijimatsu, M.
    Fujita, T.
    Nguyen, T. S.
    Rutqvist, J.
    Jing, Lanru
    KTH, Superseded Departments, Land and Water Resources Engineering.
    Thermo-hydro-mechanical characterisation of a bentonite-based buffer material by laboratory tests and numerical back analyses2001In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 38, no 1, p. 95-104Article in journal (Refereed)
    Abstract [en]

    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.

  • 13. Bäckström, A.
    et al.
    Antikainen, Janne
    Backers, Tobias
    Feng, X.
    Jing, Lanru
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Kobayashi, A.
    Koyama, Tomofumi
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Pan, P.
    Rinne, M.
    Shen, B.
    Hudson, J.A.
    Numerical modelling of unaxial compressive failure of granite with and without saline porewater2008In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 45, no 7, p. 1126-1142Article in journal (Refereed)
  • 14.
    Bäckström, Ann
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Jing, Lanru
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Koyama, Tomofumi
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    et al.,
    Numerical modelling of uniaxial compressive failure of granite with and without saline porewater2008In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 45, no 7, p. 1126-1142Article in journal (Refereed)
    Abstract [en]

    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.

  • 15. Chan, T.
    et al.
    Christiansson, R.
    Boulton, G. S.
    Ericsson, L. O.
    Hartikainen, J.
    Jensen, M. R.
    Ivars, Diego Mas
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Stanchell, F. W.
    Vistrand, P.
    Wallroth, T.
    DECOVALEX III BMT3/BENCHPAR WP4: The thermo-hydro-mechanical responses to a glacial cycle and their potential implications for deep geological disposal of nuclear fuel waste in a fractured crystalline rock mass2005In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 42, no 5-6, p. 805-827Article in journal (Refereed)
    Abstract [en]

    A number of studies related to past and on-going deep repository performance assessments have identified glaciation/ deglaciation as major future events in the next few hundred thousand years capable of causing significant impact on the long term performance of the repository system. Benchmark Test 3 (BMT3) of the international DECOVALEX III project has been designed to provide an illustrative example that explores the mechanical and hydraulic response of a fractured crystalline rock mass to a period of glaciation. The primary purpose of this numerical study is to investigate whether transient events associated with a glacial cycle could significantly influence the performance of a deep geological repository in a crystalline Shield setting. A conceptual site-scale (tens of kilometres) hydro-mechanical (HM) model was assembled based primarily on site-specific litho-structural, hydrogeological and geomechanical data from the Whiteshell Research Area in the Canadian Shield, with simplification and generalization. Continental glaciological modelling of the Laurentide ice sheet through the last glacial cycle lasting approximately 100,000 years suggests that this site was glaciated at about 60 ka and between about 22.5 and 11 ka before present with maximum ice sheet thickness reaching 2500 m and maximum basal water pressure head reaching 2000m. The ice-sheet/drainage model was scaled down to generate spatially and temporally variable hydraulic and mechanical glaciated surface boundary conditions for site-scale subsurface HM modelling and permafrost modelling. Under extreme periglacial conditions permafrost was able to develop down to the assumed 500-m repository horizon. Two- and three-dimensional coupled HM finite-element simulations indicate: during ice-sheet advance there is rapid rise in hydraulic head, high transient hydraulic gradients and high groundwater velocities 2-3 orders of magnitude higher than under nonglacial conditions; surface water recharges deeper than under nonglacial conditions; upon ice-sheet retreat, the gradients reverse; fracture zone network geometry, interconnectivity and hydraulic properties significantly influence flow domain response; residual elevated heads are preserved for 10,000s in the low-diffusivity rock; and no hydraulic jacking or shear failure occurs at depth. It was found that transient coupled modelling is necessary to capture the essence of glacial effects on Performance Assessment. Model dimensionality also significantly affects simulated results.

  • 16. Chen, Yifeng
    et al.
    Hu, Shaohua
    Wei, Kai
    Hu, Ran
    Zhou, Chuangbing
    Jing, Lanru
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Experimental characterization and micromechanical modeling of damage-induced permeability variation in Beishan granite2014In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 71, p. 64-76Article in journal (Refereed)
    Abstract [en]

    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.

  • 17. Chijimatsu, M.
    et al.
    Nguyen, T. S.
    Jing, Lanru
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    De Jonge, J.
    Kohlmeier, M.
    Millard, A.
    Rejeb, A.
    Rutqvist, J.
    Souley, M.
    Sugita, Y.
    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 results2005In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 42, no 5-6, p. 720-730Article in journal (Refereed)
    Abstract [en]

    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.

  • 18.
    Fardin, Nader
    et al.
    KTH, Superseded Departments, Land and Water Resources Engineering.
    Feng, Q.
    Stephansson, Ove
    KTH, Superseded Departments, Land and Water Resources Engineering.
    Application of a new in situ 3D laser scanner to study the scale effect on the rock joint surface roughness2004In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 41, no 2, p. 329-335Article in journal (Refereed)
  • 19. Hernqvist, Lisa
    et al.
    Fransson, Åsa
    Gustafson, Gunnar
    Emmelin, Ann
    Eriksson, Magnus
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Analyses of the grouting results for a section of the APSE tunnel at Aspo Hard Rock Laboratory2009In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 46, no 3, p. 439-449Article in journal (Refereed)
    Abstract [en]

    The grouting results for a tunnel at a depth of 450 min crystalline rock at Aspo HRL were studied. The aims were to investigate whether the methodology used resulted in a successful grouting design and producing a sufficiently dry tunnel, and whether grout penetration and inflow into the finished tunnel corresponded to the predictions. An analysis was made of data from an original cored borehole, drilled before the tunnel was constructed and mapped thoroughly with regard to fractures and transmissivities. The predicted inflow into the tunnel was calculated and found to be four times higher than the measured inflow. The latter was 51/min a long the 70 m tunnel, considered to be a good result at the current depth. New cored control boreholes were drilled along a section of the tunnel. The inflow positions and quantities in these holes, and the positions of grout found in the corresponding cores, were compared with the data from the original borehole. It was found that at the predicted positions of larger fractures, grout was observed and there was no inflow, showing that these had been successfully sealed. At the predicted positions of small fractures, no grout was visible in the cores, and small inflows showed that the grout had not sealed these fractures. The results indicated that cement-based grout successfully sealed fractures down to a hydraulic aperture of about 50 mm but not below 30 mm. This concurs with the initial design aimed at sealing fractures larger than 50 mm.

  • 20. Hudson, J. A.
    et al.
    Stephansson, O.
    Andersson, J.
    Tsang, C. F.
    Jing, Lanru
    KTH, Superseded Departments, Land and Water Resources Engineering.
    Coupled T-H-M issues relating to radioactive waste repository design and performance2001In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 38, no 1, p. 143-161Article in journal (Refereed)
    Abstract [en]

    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.

  • 21.
    Hudson, John A.
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Stephansson, Ove
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Andersson, J
    Guidance on numerical modelling of thermo-hydro-mechanical coupled processes for performance assessment of radioactive waste repositories2005In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 42, no 5-6, p. 850-870Article in journal (Refereed)
    Abstract [en]

    This paper provides advice on how to incorporate thermo-hydro-mechanical (THM) coupled processes into performance and safety assessments and design studies for radioactive waste disposal in geological formations. The advice is based on work conducted for the EU research project BENCHPAR: "Benchmark Tests and Guidance on Coupled Processes for Performance Assessment of Nuclear Waste Repositories". In Section 1, there is an explanation of why numerical analyses incorporating THM mechanisms are required for radioactive waste studies and background material on the subject is provided. Then, the THM processes and their interactions are explained in Section 2. Three case examples of THM numerical analysis are presented in Section 3 to illustrate the type of work that can be conducted to study the near-field, upscaling, and the far-field. The importance and priority of the THM couplings are summarized in Section 4. Recommended soft and hard auditing procedures are presented in Section 5. We place special emphasis on the fact that the most important step in numerical modelling is not executing the calculations per se, but the earlier conceptualization of the problem regarding the dominant processes, the material properties and parameters, the engineering perturbations, and their mathematical presentations. The associated modelling component of addressing the uncertainties and estimating their influence on the results is also important. Thus, the specific models and codes should be studied first to evaluate the harmony between the nature of the problem and the nature of the codes. The tactical use of particular numerical techniques will then be based on a sound strategic foundation. An associated listing of bullet point recommendations and issues for future directions for this THM subject area is given in Section 6.

  • 22.
    Jing, Lanru
    KTH, Superseded Departments, Land and Water Resources Engineering.
    A review of techniques, advances and outstanding issues in numerical modelling for rock mechanics and rock engineering2003In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 40, no 3, p. 283-353Article, review/survey (Refereed)
    Abstract [en]

    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.

  • 23.
    Jing, Lanru
    et al.
    KTH, Superseded Departments, Land and Water Resources Engineering.
    Hudson, J. A.
    Fundamentals of the hydro-mechanical behaviour of rock fractures: roughness characterization and experimental aspects2004In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 41, no 3, p. 383-383Article in journal (Refereed)
    Abstract [en]

    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.

  • 24.
    Jing, Lanru
    et al.
    KTH, Superseded Departments, Land and Water Resources Engineering.
    Hudson, J. A.
    Numerical methods in rock mechanics2002In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 39, no 4, p. 409-427Article, review/survey (Refereed)
    Abstract [en]

    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.

  • 25. Jing, Lanru
    et al.
    Stephansson, Ove
    Research results from the DECOVALEX III BECHPAR Projects2005In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 42, no 5-6, p. 591-870Article in journal (Refereed)
  • 26.
    Jing, Lanru
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630), Engineering Geology and Geophysics.
    Stephansson, Ove
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630), Engineering Geology and Geophysics.
    Special Issue: Research results from the DECOVALEX III & BENCHPAR projects - Preface2005In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 42, no 5-6, p. 591-592Article in journal (Other academic)
  • 27.
    Johansson, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Influence of scale and matedness on the peak shear strength of fresh, unweathered rock joints2016In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 82, p. 36-47Article in journal (Refereed)
    Abstract [en]

    It is widely recognized that the mechanical parameters for unfilled and rough rock joints, such as the peak shear strength, can vary with scale. However, due to contradictory results concerning the extent and nature of the scale effect reported in the literature, it is still a debated subject. A conceptual model developed by Johansson and Stille 2014 suggests how roughness and matedness at different scales influences the peak shear strength for fresh, rough and unweathered joint. However, the model's ability to predict how the roughness and matedness affects the peak shear strength at different scales was not verified. The aim of this paper is to investigate the ability of the conceptual model to estimate the peak shear strength at different degrees of matedness and scales. A series of direct shear test were carried out at two different scales and two different degrees of matedness. The peak shear strength from the tests was compared to the peak shear strength calculated with the conceptual model. The results showed that the model can predict the peak shear strength for both the perfectly mated and the unmated joints. No scale effect was observed in the shear tests, which is in line with the predictions using the model. The influence of matedness in combination with scale might explain some of the contradictory findings regarding the scale effect.

  • 28.
    Johansson, Fredrik
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    A conceptual model for the peak shear strength of fresh and unweathered rock joints2014In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 69, p. 31-38Article in journal (Refereed)
    Abstract [en]

    Several criteria have been proposed over the years in order to predict the peak shear strength of rock joints.The most widely used criterion is the JRC-JCS criterion by Barton. It says that changes in the peak shear strength originate from surface roughness, joint wall compressive strength and normal stress. A limitation with this criterion is that the contribution from roughness could be overestimated for natural and mismatched joints if the joint roughness coefficient, JRC, is estimated based on the direct profiling method. To account for this effect, Zhao introduced the joint matching coefficient, JMC, which accounts for the matedness of the joint. In addition to this, it is known that the scale of the sheared joint could affect the peak shear strength. However, no criterion exists that describes how roughness, matedness and scale interact. In this paper, a conceptual model is proposed. The model is based on adhesion and fractal theory, measurements of surface roughness and the anticipated variation of the number and size of the contact points. The model proposes how the compressive strength and the roughness of the joint surface together with the matedness of the joint interact in order to form the shear strength of the joint under constant normal load conditions. The model also suggests an explanation for the scale effect of rock joints with respect to the surface roughness.

  • 29. Koyama, T.
    et al.
    Neretnieks, Ivars
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Jing, Lanru
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    A numerical study on differences in using Navier-Stokes and Reynolds equations for modeling the fluid flow and particle transport in single rock fractures with shear2008In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 45, no 7, p. 1082-1101Article in journal (Refereed)
    Abstract [en]

    The study on fluid flow and transport processes of rock fractures in most practical applications involves two fundamental issues: the validity of Reynolds equation for fluid flow (as most often assumed) and the effects of shear displacements on the magnitudes and anisotropy of the fluid flow velocity field. The reason for such concerns is that the impact of the surface roughness of rock fractures is still an unresolved challenging issue. The later has been systematically investigated with results showing that shear displacement plays a dominant role on evolutions of fluid velocity fields, for both magnitudes and anisotropy, but the former has not received examinations in details due to the numerical complexities involving solution of the Navier-Stokes (NS) equations and the representations of fracture geometry during shear. The objective of this paper aims to solve this problem through a FEM modeling effort. Applying the COMSOL Multiphysics code (FEM) and assuming a 2D problem, we consider the coupled hydromechanical effect of fracture geometry change due to shear on fluid flow (velocity patterns) and particle transport (streamline/velocity dispersion), using measured topographical data of natural rock fracture surfaces. The fluid flow in the vertical 2D cross-sections of single rock fractures was simulated by solving both the Navier-Stokes and the Reynolds equation, and the particle transport was predicted by the streamline particle tracking method with calculated flow velocity fields (vectors) from the flow simulations, obtaining results such as flow velocity profiles, total flow rates, particle travel time, breakthrough curves and the Peclet number, Pe, respectively. The results obtained using NS and Reynolds equations were compared to illustrate the degree of the validity of the Reynolds equation for general applications in practice since the later is mush more computationally efficient for solving large-scale problems. The flow simulation results show that both the total flow rate and the flow velocity fields in a rough rock fracture predicted by the NS equation were quite different from those predicted by the Reynolds equation. The results show that a roughly 5-10% overestimation on the flow rate is produced when the Reynolds equation is used, and the ideal parabolic velocity profiles defined by the local cubic law, when Reynolds equation is used, is no longer valid, especially when the roughness feature of the fracture surfaces changes with shear. These deviations of flow rate and flow velocity profiles across the fracture aperture have a significant impact on the particle transport behavior and the associated properties, such as the travel time and Peclet number. The deviations increase with increasing flow velocity and become more significant when fracture aperture geometry changes with shear.

  • 30.
    Koyama, Tomofumi
    et al.
    KTH, Superseded Departments, Land and Water Resources Engineering.
    Fardin, Nader
    KTH, Superseded Departments, Land and Water Resources Engineering.
    Jing, Lanru
    KTH, Superseded Departments, Land and Water Resources Engineering.
    Shear-induced anisotropy and heterogeneity of fluid flow in a single rock fracture with translational and rotary shear displacements: a numerical study2004In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 41, no 3, p. 426-426Article in journal (Refereed)
    Abstract [en]

    The effects of rotary shear displacements on fluid flow rates and patterns under shear-flow test conditions were numerically investigated in this paper. A pair of digitized surfaces of a concrete fracture replica of size 250 x 250mm was numerically manipulated to simulate the translational and rotary shearing processes of the sample, which provided the evolution of the aperture distributions during shearing and was used to determine the evolution of the fracture transmissivity field. The translational shear test has bidirectional (x and y) hydraulic head boundary conditions and shearing in the x-direction with 1mm shear displacement interval up to 20mm. The rotary shear test has a 0.5° rotation interval up to 90°. The results of flow simulations show that with increasing rotary shear, the flow rate increases but its pattern becomes rapidly isotropic. For bi-directional translational flow, the flow rate increases with shear but significant channelling, anisotropy and heterogeneity developed with shear displacement. The above flow simulations illustrated the more realistic flow patterns under general fracture deformation modes of translation and rotation, and provided insights for the design of more flexible and complementary laboratory coupled stressflow tests.

  • 31.
    Koyama, Tomofumi
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Fardin, Nader
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Jing, Lanru
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Stephansson, Ove
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Numerical simulation of shear-induced flow anisotropy and scale-dependent aperture and transmissivity evolution of rock fracture replicas2006In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 43, no 1, p. 89-106Article in journal (Refereed)
    Abstract [en]

    Fluid flow anisotropy in a single rock fracture during a shear process is an important issue in rock mechanics and is investigated in this paper using FEM modelling, considering evolutions of aperture and transmissivity with shear displacement history. The distributions of fracture aperture during shearing with large shear displacements were obtained by numerically manipulating relative translational movements between two digitalized surfaces of a rock fracture replica, with changing sample sizes. The scale dependence of the fluid behaviour and properties were also investigated using a fractal approach. The results show that the fracture aperture increases anisotropically during shear with a more pronounced increase in the direction perpendicular to the shear displacement, causing significant fluid flow channelling effect, as also observed by other researchers. This finding may have important impacts on the interpretation of the results of coupled hydro-mechanical experiments for measurements of hydraulic properties of rock fractures because the hydraulic properties are usually calculated from flow test results along the shear directions while ignoring the more significant anisotropic flow perpendicular to the shear direction. This finding indicates that the coupled stress-flow tests of rough rock fractures should be conducted in true three-dimensions if possible. Significant change in fracture aperture/ transmissivity in the out-of-plane direction should be properly evaluated if two-dimensional tests are conducted. Results obtained from numerical simulations also show that fluid flow through a single rough fracture changes with increasing sample size and shear displacements, indicating that representative hydro-mechanical properties of the fractures in the field can only be more reliably determined using samples of large enough sizes beyond the stationarity threshold and tested with larger shear displacements.

  • 32.
    Koyama, Tomofumi
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Li, B.
    Jiang, Y.
    Jing, Lanru
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Numerical simulations for the effects of normal loading on particle transport in rock fractures during shear2008In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 45, no 8, p. 1403-1419Article in journal (Refereed)
    Abstract [en]

    Fluid flow and tracer transport in a single rock fracture during shear is investigated using the finite element method (FEM) and streamline particle tracking, 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 of feature replicas of rock fracture specimens, and shear dilations measured during the coupled shear-flow tests in laboratory. The coupled shear-flow tests were performed under two levels of constant normal loading (CNL). A special algorithm for treating the contact areas as zero-aperture elements was used to produce more accurate flow field simulations using FEM. The simulation results agreed well with the flow rate data obtained from the laboratory tests, showing complex histories of fracture aperture and tortuous flow channels with changing normal stresses and increasing shear displacements for the flow parallel with the shear direction. A greater increase was observed for flow in the direction perpendicular to the shear direction, due to the significant flow channels created by the shearing process. From the obtained flow velocity fields, particle transport was predicted using a streamline particle tracking method with the flow velocity fields (vectors) taken from the flow simulations, yielding particle travel times, breakthrough curves, and the Peclet number, Pe. The transport behavior in the fracture is also anisotropic, and advective transport is greater in the direction parallel with the shear direction. The effect of normal stress on the particle transport is significant, and dispersion becomes larger with increasing normal stress.

  • 33. Li, Bo
    et al.
    Jiang, Yujing
    Koyama, Tomofumi
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Jing, Lanru
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Tanabashi, Yoshihiko
    Experimental study of the hydro-mechanical behavior of rock joints using a parallel-plate model containing contact areas and artificial fractures2008In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 45, no 3, p. 362-375Article in journal (Refereed)
    Abstract [en]

    In recent years, geological disposal of radioactive wastes is considered to be the most promising option, which requires the understanding of the coupled mechanical, hydraulic and thermal properties of the host rock masses and rock fractures. The hydro-mechanical behavior and properties of rock fractures are usually determined by laboratory experiments on fracture specimens that serve as the basic building block of the constitutive models of fractured rock masses. Laboratory testing of rock fractures involve a number of technical issues that may have significant impacts on the reliability and applicability of the testing results, chief among them are the quantitative estimation of the evolutions of hydraulic transmissivity fields of fractures during shear under different normal constraint conditions, and the sealing techniques when fluid flow during shear is involved. In this study, a new shear-flow testing apparatus with specially designed fluid sealing techniques for rock fractures were developed, under constant normal load (CNL) or constant normal stiffness (CNS) constraint. The topographical data of all fracture specimens were measured before testing to constitute the geometrical models for simulating the change of mechanical aperture distributions during shearing. A number of shear-flow coupling tests were carried out on three kinds of rock fracture specimens to evaluate the influence of morphological properties of rock fractures on their hydro-mechanical behaviour. Some empirical relations were proposed to evaluate the effects of contact area and surface roughness on the behavior of fluid flow through rock fractures.

  • 34. Makurat, A
    et al.
    Zimmerman, R W
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630), Engineering Geology and Geophysics.
    Special issue: Rock physics and geomechanics - Preface2005In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 42, no 7-8, p. 871-872Article in journal (Other academic)
  • 35. Millard, A.
    et al.
    Rejeb, A.
    Chijimatsu, M.
    Jing, Lanru
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    De Jonge, J.
    Kohlmeier, M.
    Nguyen, T. S.
    Rutqvist, J.
    Souley, M.
    Sugita, Y.
    Numerical study of the THM effects on the near-field safety of a hypothetical nuclear waste repository - BMT1 of the DECOVALEX III project. Part 2: Effects of THM coupling in continuous and homogeneous rocks2005In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 42, no 5-6, p. 731-744Article in journal (Refereed)
    Abstract [en]

    An evaluation of the importance of the thermo-hydro-mechanical couplings (THM) on the performance assessment of a deep underground radioactive waste repository has been made as a part of the international DECOVALEX III project. It is a numerical study that simulates a generic repository configuration in the near field in a continuous and homogeneous hard rock. A periodic repository configuration comprises a single vertical borehole, containing a canister surrounded by an over-pack and a bentonite layer, and the backfilled upper portion of the gallery. The thermo-hydro-mechanical evolution of the whole configuration is simulated over a period of 100 years. The importance of the rock mass's intrinsic permeability has been investigated through scoping calculations with three values: 10(-17), 10(-18) and 10(-19) m(2). Comparison of the results predicted by fully coupled THM analysis as well as partially coupled TH, TM and HM analyses, in terms of several predefined indicators of importance for performance assessment, enables us to identify the effects of the different combinations of couplings, which play a crucial role with respect to safety issues. The results demonstrate that temperature is hardly affected by the couplings. In contrast, the influence of the couplings on the mechanical stresses is considerable.

  • 36.
    Min, Ki Bok
    et al.
    KTH, Superseded Departments, Land and Water Resources Engineering.
    Jing, Lanru
    KTH, Superseded Departments, Land and Water Resources Engineering.
    Stress-dependent mechanical properties and bounds of Poisson's ratio for fractured rock masses investigated by a DFN-DEM technique2004In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 41, no 3, p. 431-432Article in journal (Refereed)
  • 37.
    Min, Ki Bok
    et al.
    KTH, Superseded Departments, Land and Water Resources Engineering.
    Rutqvist, J
    Tsang, C F
    Jing, Lanru
    KTH, Superseded Departments, Land and Water Resources Engineering.
    Stress-dependent permeability of fractured rock masses: a numerical study2004In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 41, no 7, p. 1191-1210Article in journal (Refereed)
    Abstract [en]

    We investigate the stress-dependent permeability issue in fractured rock masses considering the effects of nonlinear normal deformation and shear dilation of fractures using a two-dimensional distinct element method program, UDEC, based on a realistic discrete fracture network realization. A series of "numerical" experiments were conducted to calculate changes in the permeability of simulated fractured rock masses under various loading conditions. Numerical experiments were conducted in two ways: (1) increasing the overall stresses with a fixed ratio of horizontal to vertical stresses components; and (2) increasing the differential stresses (i.e., the difference between the horizontal and vertical stresses) while keeping the magnitude of vertical stress constant. These numerical experiments show that the permeability of fractured rocks decreases with increased stress magnitudes when the stress ratio is not large enough to cause shear dilation of fractures, whereas permeability increases with increased stress when the stress ratio is large enough. Permeability changes at low stress levels are more sensitive than at high stress levels due to the nonlinear fracture normal stress-displacement relation. Significant stress-induced channeling is observed as the shear dilation causes the concentration of fluid flow along connected shear fractures. Anisotropy of permeability emerges with the increase of differential stresses, and this anisotropy can become more prominent with the influence of shear dilation and localized flow paths. A set of empirical equations in closed-form, accounting for both normal closure and shear dilation of the fractures, is proposed to model the stress-dependent permeability. These equations prove to be in good agreement with the results obtained from our numerical experiments.

  • 38. Min, Ki-Bok
    Thermo-mechanical impacts on performance of a nuclear waste repository in fractured rock masses – a far-field study using an equivalent continuum approach2005In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 42, no 5-6, p. 765-780Article in journal (Refereed)
  • 39.
    Min, Ki-Bok
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Rutqvist, J
    Tsang, C F
    Jing, Lanru
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Thermally induced mechanical and permeability changes around a nuclear waste repository - a far-field study based on equivalent properties determined by a discrete approach2005In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 42, no 5-6, p. 765-780Article in journal (Refereed)
    Abstract [en]

    A numerical investigation is conducted on the impacts of the thermal loading history on the evolution of mechanical response and permeability field of a fractured rock mass containing a hypothetical nuclear waste repository. The geological data are extracted from the site investigation results at Sellafield, England. A combined methodology of discrete and continuum approaches is presented. The results of a series of simulations based on the DFN-DEM (discrete fracture network-distinct element method) approach provide the mechanical and hydraulic properties of fractured rock masses, and their stress-dependencies. These properties are calculated on a representative scale that depends on fracture network characteristics and constitutive models of intact rock and fractures. In the present study, data indicate that the large scale domain can be divided into four regions with different property sets corresponding to the depth. The results derived by the DFN-DEM approach are then passed on to a large-scale analysis of the far-field problem for the equivalent continuum analysis. The large-scale far-field analysis is conducted using a FEM code, ROCMAS for coupled thermo-mechanical process. The results show that the thermal stresses of fractured rock masses vary significantly with mechanical properties determined at the representative scale. Vertical heaving and horizontal tensile displacement are observed above the repository. Observed stress and displacement fields also shows significant dependency on how the mechanical properties are characterized. The permeability changes induced by the thermal loading show that it generally decreases close to the repository. However, change of permeability is small, i.e., a factor of two, and thermally induced dilation of fracture was not observed. Note that the repository excavation effects were not considered in the study. The work presented in this paper is the result of efforts on a benchmark test (BMT2) within the international co-operative projects DECOVALEX III and BENCHPAR.

  • 40. Nguyen, T. S.
    et al.
    Borgesson, L.
    Chijimatsu, M.
    Rutqvist, J.
    Fujita, T.
    Hernelind, J.
    Kobayashi, A.
    Ohnishi, Y.
    Tanaka, M.
    Jing, Lanru
    KTH, Superseded Departments, Land and Water Resources Engineering.
    Hydro-mechanical response of a fractured granitic rock mass to excavation of a test pit - the Kamaishi Mine experiment in Japan2001In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 38, no 1, p. 79-94Article in journal (Refereed)
    Abstract [en]

    A thermo-hydro-mechanical experiment was conducted in a fractured granitic ruck mass at the Kamaishi Mine in Japan. The experiment consists of the excavation of a cylindrical test pit on the floor of an experimental drift. The test pit was then lilted with bentonite with an embedded heater. During the excavation of the test pit, the hydromechanical response of the surrounding rock was monitored. This paper presents the efforts of four research teams to numerically simulate the hydro-mechanical response of the rock mass during excavation. While the total inflow rate to the test pit, the flow distribution on the pit walls and the displacements in the rock mass away From the pit could be reasonably predicted, the pore pressure in individual boreholes, and the expansion behaviour of the pit were less successfully simulated. The reasons for these discrepancies are discussed in the paper.

  • 41.
    Noorian-Bidgoli, Majid
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. University of Kashan, Iran.
    Jing, Lanru
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Stochastic analysis of strength and deformability of fractured rocks using multi-fracture system realizations2015In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 78, p. 108-117Article in journal (Refereed)
  • 42. Place, Joachim
    et al.
    Nejad Ghafar, Ali
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Malehmir, Alireza
    Draganovic, Almir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    On using the thin fluid-layer approach at ultrasonic frequencies for characterising grout propagation in an artificial fracture2016In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 89, p. 68-74Article in journal (Refereed)
    Abstract [en]

    We investigate the ultrasonic transport properties of such an idealised fracture whose 100 µm aperture is about 0.02 the wavelength, and filled with various fluids flowing under external forcing. As the artificial fracture is made of two solid and parallel walls separated by a thin fluid layer, we use the thin fluid layer concept to study the compressional (P-) wavefield transmitted across and reflected off the fracture, with no mode-conversion considered. We demonstrate that air and various fluids (water, grouts of varied w/c – water to cement ratio) can be distinguished when injected into the fracture, both at atmospheric pressure or under over-pressure as done in real grouting cases in the field. Then, using an analytical solution, we verify our experimental data and predict the results that can be obtained with a different fracture aperture. Our results illustrate that replicating such ultrasonic measurements both in space and time would allow successfully monitoring the grout propagation within an artificial fracture.

  • 43. Rutqvist, J.
    et al.
    Borgesson, L.
    Chijimatsu, M.
    Kobayashi, A.
    Jing, Lanru
    KTH, Superseded Departments, Land and Water Resources Engineering.
    Nguyen, T. S.
    Noorishad, J.
    Tsang, C. F.
    Thermohydromechanics of partially saturated geological media: governing equations and formulation of four finite element models2001In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 38, no 1, p. 105-127Article in journal (Refereed)
    Abstract [en]

    This paper presents the general governing equations for coupled thermohydromechanical (THM) processes in saturated and unsaturated geologic formations and reviews four finite element codes fur modeling of such system. Three of the codes are developed for the special purpose of analyzing coupled THM processes in unsaturated porous and fractured geological media, and the fourth is a commercial code that has been used in its standard version, with a few adaptations for this specialized problem. The basic assumptions and fundamental equations for coupled THM processes in unsaturated porous fractured rock are presented. and formulations of the four finite element models are compared.

  • 44. Rutqvist, J.
    et al.
    Borgesson, L.
    Chijimatsu, M.
    Nguyen, T. S.
    Jing, Lanru
    KTH, Superseded Departments, Land and Water Resources Engineering.
    Noorishad, J.
    Tsang, C. F.
    Coupled thermo-hydro-mechanical analysis of a heater test in fractured rock and bentonite at Kamaishi Mine - comparison of field results to predictions of four finite element codes2001In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 38, no 1, p. 129-142Article in journal (Refereed)
    Abstract [en]

    Four computer codes were applied for a prediction of coupled thermo-hydro-mechanical responses during an in situ heater experiment which simulates a nuclear waste deposition hole with a waste over-pack and bentonite buffer, surrounded by fractured rock. The elevated temperature in the heater surroundings, which was maintained at 100 C for 8.5 months, generated substantial heat-driven moisture flow and swelling in the clay buffer, and thermal expansion of the surrounding fractured rock. Predicted system responses - including temperature. moisture content, fluid pressure, stress and displacement - were compared to measurements at 70 sensors located both in the clay buffer and the near-field rock. An overall good agreement between modeling and measured results indicates that most thermo-hydro-mechanical responses are fairly well represented by the coupled numerical models. Uncertainties occur for modeling of hydromechanical behavior of the swelling clay buffer at low saturation, modeling of near-field heterogeneous mechanical behavior of the low-stressed fractured reek, and modeling of the rock-buffer interface.

  • 45. Rutqvist, J.
    et al.
    Chijimatsu, M.
    Jing, Lanru
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Millard, A.
    Nguyen, T. S.
    Rejeb, A.
    Sugita, Y.
    Tsang, C. F.
    A numerical study of THM effects on the near-field safety of a hypothetical nuclear waste repository - BMT1 of the DECOVALEX III project. Part 3: Effects of THM coupling in sparsely fractured rocks2005In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 42, no 5-6, p. 745-755Article in journal (Refereed)
    Abstract [en]

    As a part of the international DECOVALEX III project, and the European BENCHPAR project, the impact of thermal-hydrological-mechanical (THM) couplings on the performance of a bentonite-back-filled nuclear waste repository in near-field crystalline rocks is evaluated in a Bench-Mark Test problem (BMT1) and the results are presented in a series of three companion papers in this issue. This is the third paper with focuses on the effects of THM processes at a repository located in a sparsely fractured rock. Several independent coupled THM analyses presented in this paper show that THM couplings have the most significant impact on the mechanical stress evolution, which is important for repository design, construction and post-closure monitoring considerations. The results show that the stress evolution in the bentonite-back-filled excavations and the surrounding rock depends on the post-closure evolution of both fields of temperature and fluid pressure. It is further shown that the time required to full resaturation may play an important role for the mechanical integrity of the repository drifts. In this sense, the presence of hydraulically conducting fractures in the near-field rock might actually improve the mechanical performance of the repository. Hydraulically conducting fractures in the near-field rocks enhances the water supply to the buffers/back-fills, which promotes a more timely process of resaturation and development of swelling pressures in the back-fill, thus provides timely confining stress and support to the rock walls. In one particular case simulated in this study, it was shown that failure in the drift walls could be prevented if the compressive stresses in back-fill were fully developed within 50 yr, which is when thermally induced rock strain begins to create high differential (failure-prone) stresses in the near-field rocks. Published by Elsevier Ltd.

  • 46.
    Tong, Fuguo
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Jing, Lanru
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Zimmerman, Robert W.
    A fully coupled thermo-hydro-mechanical model for simulating multiphase flow, deformation and heat transfer in buffer material and rock masses2010In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 47, no 2, p. 205-217Article in journal (Refereed)
    Abstract [en]

    This paper presents a numerical method for modeling coupled thermo-hydro-mechanical processes of geomaterials with multiphase fluid flow. A FEM code has been developed and validated for modeling the behavior of porous geological media, and is equally applicable for modeling coupled THM processes in rocks. The governing equations are based on the theory of mixtures applied to the multiphysics of porous media, considering solid phase deformation, multiphase fluid flow, and heat transport. New numerical techniques have been developed for more efficient FEM formulation and equation solution for modeling saturated or partially saturated water flow, gas flow and heat transfer indeformable porous media, as are commonly encountered in performance and safety assessment of underground radioactive repositories. The code has been validated against an experimental benchmark test, which involves bentonite under laboratory conditions, with good results. Several critical outstanding issues for modeling coupled processes of geomaterials are discussed indepth.

  • 47.
    Tong, Fuguo
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Jing, Lanru
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Zimmerman, Robert W.
    An effective thermal conductivity model of geological porous media for coupled thermo-hydro-mechanical systems with multiphase flow2009In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 46, no 8, p. 1358-1369Article in journal (Refereed)
    Abstract [en]

    The objective of this paper is to present the development of an effective thermal conductivity model for simulation of thermo-hydro-mechanical processes of geological porous media. The Wiener bounds and Hashin-Shtrikman bounds for thermal conductivity of three-phase mixture are introduced first, followed by descriptions of thermal conductivities of gas, water and solid, respectively. The derivation of a new effective thermal conductivity model, in closed form, is then presented. The model considers the combined effects of solid mineral composition, temperature, liquid saturation degree, porosity and pressure on the effective thermal conductivity of porous media, when multiphase flow with phase change is involved. The model strictly obeys the Wiener bounds (for anisotropic media) and Hashin-Shtrikman bounds (for isotropic media) over wide ranges of porosities and saturations, and the predicted results agrees very well with the experimental data for MX80 bentonite, compared with Johansen's method. An experimental benchmark test problem under laboratory conditions for coupled thermo-hydro-mechanical processes of compacted FEBEX bentonite is simulated for validation of the model, and the results show that the model provides improved predictions of the evolution and distribution of temperature, with simpler forms of mathematical functions. (C) 2009 Elsevier Ltd. All rights reserved.

  • 48. Tsang, C. F.
    et al.
    Jing, Lanru
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Stephansson, O.
    Kautsky, F.
    The DECOVALEX III project: A summary of activities and lessons learned2005In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 42, no 5-6, p. 593-610Article in journal (Refereed)
    Abstract [en]

    Initiated in 1992, the DECOVALEX project is an international collaboration for advancing the understanding and modeling of coupled thermo-hydro-mechanical (THM) processes in geologic systems. The project has made important scientific achievements through three stages and is progressing in its fourth stage. It has played a key role in the development of mathematical modeling and in situ testing of coupled THM processes in fractured rock and buffer/backfill materials, a subject of importance for performance assessment of radioactive waste geologic repositories. This paper summarizes studies under the most recent stage of the project, DECOVALEX III (2000-2003). These studies include those of two major field experiments: (a) the FEBEX experiment at Grimsel, Switzerland, investigating coupled THM processes in a crystalline rock-bentonite system, and (b) the Drift Scale Test (DST) experiment at Yucca Mountain, Nevada, investigating coupled THM processes in unsaturated tuff. These are two of the largest multiyear heater tests undertaken to date for the study of coupled THM processes in geological systems. In addition, three so-called benchmark tests are also studied to evaluate the impact of coupled THM processes under different scenarios and geometries. Within the DECOVALEX project, multiple research teams participated in each of the studies, using different approaches and computer codes. Comparisons of results have provided insight into coupled THM processes, which in turn has stimulated further development of our modeling capabilities. Lessons learned from these studies are discussed. The scientific advances and enhanced insight gained through this kind of international cooperation illustrate the effectiveness of the DECOVALEX project.

  • 49. Weddfelt, K.
    et al.
    Saadati, Mahdi
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Larsson, Per-Lennart
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    On the load capacity and fracture mechanism of hard rocks at indentation loading2017In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 100, p. 170-176Article in journal (Refereed)
    Abstract [en]

    The load capacity of selected hard rocks subjected to circular flat punch indentation is investigated. The compacted zone underneath the indenter is assumed to be limited and only responsible for the load transition to the rest of the material. Therefore, the theory of elasticity is used to define the stress state in a semi-infinite medium loaded by a flat punch indenter. The final load capacity is related to the formation of a sub-surface median crack that initiates due to tensile hoop (circumferential) stresses. Therefore the final failure should occur at a force level in which the hoop stress is greater than the tensile strength of the rock. Since the tensile stress is distributed over a volume of material, tensile crack failure can occur at different locations with tensile hoop stress depending on where the most critical flaw is located. Therefore, the initiation of the median crack that should be responsible for the final load capacity is treated as a probabilistic phenomenon. This process is described by Weibull theory which will be used as a failure criterion. It is assumed here that the opening of median crack triggers a final violent rupture, therefore the assumption in Weibull theory, that the final failure occurs as soon as a macroscopic fracture initiates from a microcrack is fulfilled. The effective volume is calculated for a semiinfinite medium loaded by a flat punch indenter. The material properties of Bohus granite obtained from three point bending tests are used as reference values in describing the Weibull size effect. The experimental results for the stamp load capacity of three selected hard rocks are taken from the literature. They are considered similar rocks to the reference material in this paper, which is Bohus granite. The model describes the observed load capacity with a very good accuracy for all three rocks. It is likely that the presently proposed methodology is applicable for other types of semi-brittle materials and indenter shapes.

  • 50. Zhao, Z.
    et al.
    Liu, Longcheng
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Neretnieks, Ivars
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Jing, Lanru
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Solute transport in a single fracture with time-dependent aperture due to chemically medicated changes2014In: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 66, p. 69-75Article in journal (Refereed)
    Abstract [en]

    In addition to mechanical loading, the transport properties of rock fractures are also affected by chemically mediated changes, such as pressure solution, stress corrosion and free-face dissolution, among others. Based on a time-dependent model of fracture closure under constant normal stresses, the transport behavior of contaminants in a slowly closing fracture is studied using a finite difference scheme. The results show that the contaminant penetrating along the fracture plane gradually becomes slow or almost negligible during the process of fracture closure induced by chemical processes, whereas the matrix diffusion of contaminants is active all the time. This finding indicates that diffusion into the rock matrix perpendicular to the advective flow direction always plays an important role in determining the fate of contaminant in rock fractures. The smaller the fluid flow due to fracture closure and the larger impact the matrix diffusion can further delay the solute transport.

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