Laws for Coupled Analysis of Seepage Flow in Soft Rock

1. Laws for Coupled Analysis of Seepage Flow in Soft Rock Li Peng Li Yan tunnelee@163.com.cn 3rd China-Japan Joint Seminar for the Graduate Students

2. Content • Introduction of soft rock and present research state • Characteristics of seepage deformation of soft rock • Characteristics of seepage flow coupling of soft rock • FEM soft for coupling analysis based on MATLAB 3rd China-Japan Joint Seminar for the Graduate Students

3. Introduction of soft rock • Widely distributed around the world • Mainly made up of mud-stone and cleaving-stone • Including sedimentary deposit, weak interlayer, joint plane, discontinuous fracture face, array of particles and agglomerations, micro-pore and micro-fracture etc. • Obvious variability and anisotropy • Greatly influenced by water • Exist in railway, highway, mine, hydraulic power engineering etc. 3rd China-Japan Joint Seminar for the Graduate Students

4. Present research state of seepage flow coupling analysis Porous media seepage flow • In the 1970s, Biot’s theory was widely used for the porous rock • Zhujiang Shen (1977) firstly studied consolidation through FEM based on Biot’s consolidation theory • Rock stress coupling research was made by Noorishad (1982 1990) • Curran (1987) made a study of porous media consolidation through BEM displacement discontinuous model • Elastic porous media seepage flow coupling control equations denoted as: 3rd China-Japan Joint Seminar for the Graduate Students

5. Fracture media seepage flow Single fracture face seepage flow • Cube law • Lomize and Louis’s experiment through imitated natural fracture Fracture net seepage flow • Double media model Snow (1968), Oda (1986), Yuxing Xiao (1997 1999) • Non-double media model (Equivalent continuous media model & Discrete fracture media model) Wilson&Witherspoon (1974), Noorishad (1985), Enzhi Wang (1998), Xiaoming Ji (2003) 3rd China-Japan Joint Seminar for the Graduate Students

6. Characteristics of seepage deformation of soft rock Influencing factor Rock and structural surface character • Worotnicki (1993) divided rocks as follows: 1) quartz-feldspathic-rocks (Granite, Quartzy-sandstone, Granulite etc.) 2) lithic-rocks (Lithic-sandstone, Amphibolite etc.) 3) pelitic-rocks (Mud-stone, Slate, Phyllite etc.) 4) carbonate rocks (Lime-stone, Dolomite etc.) According to 200 groups tests, pelitic-rocks represent the most anisotropic properties. 3rd China-Japan Joint Seminar for the Graduate Students

7. a) quartz-feldspathic-rocks & carbonate rocks b) pelitic-rocks c) carbonate rocks 3rd China-Japan Joint Seminar for the Graduate Students

8. Man-chao He (2002) made single axle compression test of siltstone and got a result of mechanical index alteration correlated with the included angle of compression stress and structural face direction 3rd China-Japan Joint Seminar for the Graduate Students

9. Rock environmental field • Stress field, seepage flow field and temperature field • Zhi-jun Feng (2005) made triaxial tests of three typical soft rock and got a result of Young’s modulus considering of natural and saturated moisture content with different confining pressure 3rd China-Japan Joint Seminar for the Graduate Students

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11. Equivalent transverse isotropic model • Goodman (1968) introduced this model to simulate regular joint rock • Basic element • Shearing performance • Compressing performance 3rd China-Japan Joint Seminar for the Graduate Students

12. For the complex joints, assume three groups different direction joints which parallel n, s, t axis (①, ②, ③ axis) • According to displacement equivalent law • Rock constitutive equations (i=1,2,3 or n,s,t) (i, j=1,2,3 or n,s,t) 3rd China-Japan Joint Seminar for the Graduate Students

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14. Young’s modulus • Affects from different confining pressure • Affects from stratification plane direction vertical parallel Brown-red mudstone full stress-strain curve under different confining pressures Brown-red mudstone stress-strain curve of vertical&parallel stratification plane 3rd China-Japan Joint Seminar for the Graduate Students

15. Characteristics of seepage flow coupling of soft rock Anisotropy seepage flow properties • Basic equations: • Tensor transformation 3rd China-Japan Joint Seminar for the Graduate Students

16. Seepage flow-stress coupling control equations • Coupling representation or • Empirical equations Louis (1974) Gale (1982) Yuan-tian Zhou (1998) • Indirect equations Baton (1985) 3rd China-Japan Joint Seminar for the Graduate Students

17. Principle stress and permeability directions • Kozeny theory & Timoshenko method • Principle stress and permeability directions coincide (i=1,2,3) (i=1,2,3) 3rd China-Japan Joint Seminar for the Graduate Students

18. Principle stress and permeability directions mismatch 3rd China-Japan Joint Seminar for the Graduate Students

19. Experimental investigation • Quantitative analysis based on the subject study tests • Principle permeability directions assumed as the tangential directions of the joint surface • Larger difference of confining pressure and axial pressure, greater affects to permeability considering of the joint surface included angle • Test materials from highway tunnel sites, in Yun Nan province mud-siltstone and brown-red-mudstone test samples taken from rock mass which cross or parallel the joint surfaces cylinder test with a diameter of 50mm and height of 80~84mm 3rd China-Japan Joint Seminar for the Graduate Students

20. Permeability coefficient—included angle of stratification face curve considering of different axis pressure Permeability coefficient—included angle of stratification face curve considering of different confining pressure 3rd China-Japan Joint Seminar for the Graduate Students

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22. Mud-siltstone parallel joint & curve 3rd China-Japan Joint Seminar for the Graduate Students

23. Mud-siltstone vertical joint & curve 3rd China-Japan Joint Seminar for the Graduate Students

24. Brown-red mudstone parallel joint & curve 3rd China-Japan Joint Seminar for the Graduate Students

25. Brown-red mudstone vertical joint & curve 3rd China-Japan Joint Seminar for the Graduate Students

26. FEM soft for coupling analysis based on MATLAB Iterative coupling method Seepage flow field module Input Output Seepage flow boundary Form dis-field body force Coupling module Output Dis-field module Input 3rd China-Japan Joint Seminar for the Graduate Students

27. Analysis example • Manxie No.2 tunnel, multiple arch tunnel, with a length of 225m Geologic section Tunnel cross-section 3rd China-Japan Joint Seminar for the Graduate Students

28. Mother rock mainly made up of slightly weathered silty-sand rock and highly weathered sandy-mud rock • Fault above the tunnel • Embedded depth 32m according to the calculation profile • In the finite element method analysis, 2468 nodes and 2502 elements Calculation model Calculation meshes 3rd China-Japan Joint Seminar for the Graduate Students

29. First work step water pressure distribution Fifth work step water pressure distribution Last work step water pressure distribution Ultimate seepage quantity vector 3rd China-Japan Joint Seminar for the Graduate Students

30. Nephogram of X-dis sgmx sgmy Y-dis sgmxy of last work step 3rd China-Japan Joint Seminar for the Graduate Students

31. (solid lines represent non-coupling analysis results dashed lines represent coupling analysis results) Contour line of X-dis sgmx sgmy Y-dis sgmxy of last work step 3rd China-Japan Joint Seminar for the Graduate Students

32. Interpretation of the results • Differences between non-coupling and coupling analysis results • Comparison according to monitoring result monitor Left-hole circumferential nodes K3+490 section vault monitor 3rd China-Japan Joint Seminar for the Graduate Students

33. Fifth work step left hole vault displacement contrast Coupling Coupling Non-coupling Monitoring results Non-coupling Fifth work step left hole circumferential nodes displacement contrast 3rd China-Japan Joint Seminar for the Graduate Students

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35. Conclusions • when the water pressure is very high, seepage flow may have great effects on the host rock and the structure • coupling process has little effect on water pressure distribution of seepage field • under different operating modes, coupling has different effects on the displacement field • according to the FEM procedure based on MATLAB, the rapidity of convergence is very fast 3rd China-Japan Joint Seminar for the Graduate Students

36. Glimpses on seepage flow coupling problemsa brief report by Li Peng Thank you for your kind attention 3rd China-Japan Joint Seminar for the Graduate Students