Tunnel and Underground Space (터널과지하공간)

Korean Society for Rock Mechanics and Rock Engineering (한국암반공학회)
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The DFN-DEM Approach Applied to Investigate the Effects of Stress on Mechanical and Hydraulic Rock Mass Properties at Forsmark, Sweden

암반균열망-개별요소법 수치실험을 통해 살펴본 스웨덴 포쉬마크지역 암반의 역학적 및 수리적 물성에 초기응력이 미치는 영향

  • Received : 2011.04.11
  • Accepted : 2011.04.22
  • Published : 2011.04.30
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Abstract

The purpose of this study is to demonstrate the effect of in-situ rock stresses on the deformability and permeability of fractured rocks. Geological data were taken from the site investigation at Forsmark, Sweden, conducted by Swedish Nuclear Fuel and Waste Man-agement Company (SKB). A set of numerical experiments was conducted to determine the equivalent mechanical properties (essentially, elastic moduli and Poisson's ratio) and permeability, using a Discrete Fracture Network-Discrete Element Method (DFN-DEM) approach. The results show that both mechanical properties and permeability are highly dependent on stress because of the hyperbolic nature of the stiffness of fractures, different closure behavior of fractures, and change of fluid pathways caused by deformation. This study shows that proper characterization and consideration of in-situ stress are important not only for boundary conditions of a selected site but also for the understanding of the mechanical and hydraulic behavior of fractured rocks.

균열암반의 역학적 및 수리적 성질에 암반 초기응력이 미치는 영향을 고찰하였다. 지질 데이터는 스웨덴 원전원료 및 방사성 폐기물 관리회사(SKB)에 의해 수행된 포쉬마크지역의 부지조사로부터 획득되었으며 암반균열망-개별요소법 수치실험(Discrete Fracture Network - Discrete Element Method) 을 통하여 암반의 등가역학적 및 등가수리적 물성을 결정하였다. 수치실험결과 균열 강성의 응력의존성, 균열 방향에 따른 상이한 변형거동, 균열거동에 따른 수리유동 경로의 변화 등의 원인에 의하여 등가역학적 및 등가수리적 물성은 응력의존성이 큰 것을 확인하였다. 본 연구의 결과는 암반 초기응력의 정확한 예측이 특정 부지에서의 경계조건으로서뿐만 아니라 균열암반의 역학적 및 수리적 물성을 이해하는 데도 중요한 역할을 한다는 것을 보여준다.

Keywords

References

  1. Bai, M. and D. Elsworth, 1994, Modeling of subsidence and stress-dependent hydraulic conductivity for intact and fractured porous media, Rock Mech Rock Engng 27.4, 209-234. https://doi.org/10.1007/BF01020200
  2. Barton, C.A. M.D. Zoback and D. Moos, 1995, Fluid flow along potentially active faults in crystalline rock, Geology 23.8, 683-686. https://doi.org/10.1130/0091-7613(1995)023<0683:FFAPAF>2.3.CO;2
  3. Barton, N., 1982, Modelling rock joint behaviour from in-situ block tests: implications for nuclear waste repository design. Office of Nuclear Waste Isolation, Columbus, OH, ON-WI-308.
  4. Bhasin, R. and K. Hoeg, 1998, Numerical modelling of block size effects and influence of joint properties in multiply jointed rock, Tunnelling and Underground Space Technology 13.2, 181-188. https://doi.org/10.1016/S0886-7798(98)00046-7
  5. Chryssanthakis P, 2003, Forsmark site investigation - Borehole KFM01A: Results of tilt test-ing, SKB Report, P-03-108, Stockholm.
  6. Hart, R.D., P.A. Cundall and M.L. Cramer, 1985, Analysis of a loading test on a large basalt block. 26th US Symp. on Rock Mech:759-768, Rapid City, IA, USA.
  7. Itasca Consulting Group, 2000, UDEC user's guide, Ver. 3.1, Minnesota.
  8. La Pointe, P.R., 2002, Derivation of parent fracture population statistics from trace length measurements of fractal fracture populations, Int. J. Rock Mech. Min. Sci 39.3, 381-388. https://doi.org/10.1016/S1365-1609(02)00021-7
  9. Min, K.-B. and L. Jing, 2003, Numerical determination of the equivalent elastic compliance tensor for fractured rock masses using the distinct element method, Int. J. Rock Mech. Min. Sci 40.6, 795-816. https://doi.org/10.1016/S1365-1609(03)00038-8
  10. Min, K.-B. and L. Jing, 2004, Stress dependent mechanical properties and bounds of Poisson's ratio for fractured rock masses investigated by a DFN-DEM technique, Int. J. Rock Mech. Min. Sci 41.3, 431-432. https://doi.org/10.1016/j.ijrmms.2003.12.072
  11. Min, K.-B., J. Rutqvist, C.-F. Tsang, and L. Jing, 2004, Stress-dependent permeability of fractured rock masses: a numerical study, Int. J. Rock Mech. Min. Sci 41.7, 1191-1210. https://doi.org/10.1016/j.ijrmms.2004.05.005
  12. Min K.-B., O. Stephansson and L. Jing, 2005, Effect of stress on mechanical and hydraulic rock mass properties - application of DFN-DEM approach on the data from Site Investiga-tion at Forsmark, Sweden, EUROCK 2005, Brno, Czech Republic, 389-395
  13. Rutqvist, J. and O. Stephansson, 2003, The role of hydromechanical coupling in fractured rock engineering, Hydrogeology Journal 11.1, 7-40. https://doi.org/10.1007/s10040-002-0241-5
  14. Svensk Karnbranslehantering AB, 2004, Preliminary site description Forsmark area - Ver-sion 1.1, SKB R 04-15, Stockholm.
  15. Zhang, X. and D.J. Sanderson, 2002, Numerical Modelling and Analysis of Fluid Flow and Deformation of Fractured Rock Masses, Pergamon, Oxford.