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3rd China-Japan Joint Seminar for the Graduate Students1 Laws for Coupled Analysis of Seepage Flow in Soft Rock Li Peng Li Yan

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3rd China-Japan Joint Seminar for the Graduate Students2 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

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3rd China-Japan Joint Seminar for the Graduate Students3 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.

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3rd China-Japan Joint Seminar for the Graduate Students4 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 ( ) Curran (1987) made a study of porous media consolidation through BEM displacement discontinuous model Elastic porous media seepage flow coupling control equations denoted as:

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3rd China-Japan Joint Seminar for the Graduate Students5 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 ( ) Non-double media model (Equivalent continuous media model & Discrete fracture media model) Wilson&Witherspoon (1974), Noorishad (1985), Enzhi Wang (1998), Xiaoming Ji (2003)

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3rd China-Japan Joint Seminar for the Graduate Students6 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.

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3rd China-Japan Joint Seminar for the Graduate Students7 a) quartz-feldspathic-rocks & carbonate rocks b) pelitic-rocks c) carbonate rocks

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3rd China-Japan Joint Seminar for the Graduate Students8 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

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3rd China-Japan Joint Seminar for the Graduate Students9 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

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3rd China-Japan Joint Seminar for the Graduate Students10 Rock materials Natural (MPa)Saturated (MPa) Confining pressureYoung’s modulusConfining pressureYoung’s modulus Sand stone Mud stone Silt stone

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3rd China-Japan Joint Seminar for the Graduate Students11 Equivalent transverse isotropic model Goodman (1968) introduced this model to simulate regular joint rock (a)Basic element (b)Shearing performance (c)Compressing performance

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3rd China-Japan Joint Seminar for the Graduate Students12 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)

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3rd China-Japan Joint Seminar for the Graduate Students13

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3rd China-Japan Joint Seminar for the Graduate Students14 Young’s modulus Affects from different confining pressure Affects from stratification plane direction Brown-red mudstone full stress-strain curve under different confining pressures Brown-red mudstone stress-strain curve of vertical¶llel stratification plane vertical parallel

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3rd China-Japan Joint Seminar for the Graduate Students15 Characteristics of seepage flow coupling of soft rock Anisotropy seepage flow properties Basic equations: Tensor transformation

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3rd China-Japan Joint Seminar for the Graduate Students16 Seepage flow-stress coupling control equations Coupling representation or Empirical equations Louis (1974) Gale (1982) Yuan-tian Zhou (1998) Indirect equations Baton (1985)

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3rd China-Japan Joint Seminar for the Graduate Students17 Principle stress and permeability directions Kozeny theory & Timoshenko method Principle stress and permeability directions coincide (i=1,2,3)

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3rd China-Japan Joint Seminar for the Graduate Students18 Principle stress and permeability directions mismatch

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3rd China-Japan Joint Seminar for the Graduate Students19 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

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3rd China-Japan Joint Seminar for the Graduate Students20 Permeability coefficient—included angle of stratification face curve considering of different confining pressure Permeability coefficient—included angle of stratification face curve considering of different axis pressure

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3rd China-Japan Joint Seminar for the Graduate Students21 Rock materialsRelation between permeability directions & joint surface Serial number Range of coefficient of permeability (ms -1 ) Mud-siltstone parallel 70 （ 1.06 ～ 1.39 ） × （ 0.95 ～ 1.50 ） ×10 － 9 95 （ 1.09 ～ 2.51 ） ×10 － 9 vertical 101 （ 2.25 ～ 3.47 ） ×10 － （ 1.16 ～ 3.83 ） ×10 － （ 1.86 ～ 3.85 ） ×10 － 9 Brown-red- mudstone parallel 164 （ 0.98 ～ 2.82 ） ×10 － （ 0.28 ～ 1.57 ） ×10 － （ 0.27 ～ 0.69 ） ×10 － 13 vertival 173 （ 0.73 ～ 1.82 ） ×10 － （ 0.83 ～ 3.21 ） ×10 － （ 0.20 ～ 0.91 ） ×10 － 13

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3rd China-Japan Joint Seminar for the Graduate Students22 Mud-siltstone parallel joint & curve

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3rd China-Japan Joint Seminar for the Graduate Students23 Mud-siltstone vertical joint & curve

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3rd China-Japan Joint Seminar for the Graduate Students24 Brown-red mudstone parallel joint & curve

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3rd China-Japan Joint Seminar for the Graduate Students25 Brown-red mudstone vertical joint & curve

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3rd China-Japan Joint Seminar for the Graduate Students26 FEM soft for coupling analysis based on MATLAB Iterative coupling method Input OutputInput Output Seepage flow field module Seepage flow boundary Dis-field module Form dis-field body force Coupling module

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3rd China-Japan Joint Seminar for the Graduate Students27 Analysis example Manxie No.2 tunnel, multiple arch tunnel, with a length of 225m Tunnel cross-section Geologic section

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3rd China-Japan Joint Seminar for the Graduate Students28 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 modelCalculation meshes

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3rd China-Japan Joint Seminar for the Graduate Students29 First work step water pressure distribution Last work step water pressure distribution Fifth work step water pressure distribution Ultimate seepage quantity vector

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3rd China-Japan Joint Seminar for the Graduate Students30 Nephogram of X-dis Y-dis sgmxsgmy sgmxy of last work step

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3rd China-Japan Joint Seminar for the Graduate Students31 Contour line of X-dissgmxsgmy Y-dissgmxy of last work step (solid lines represent non-coupling analysis results dashed lines represent coupling analysis results)

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3rd China-Japan Joint Seminar for the Graduate Students32 Interpretation of the results Differences between non-coupling and coupling analysis results Comparison according to monitoring result Itemsx-direction displacement y-direction displacement x-direction stress y-direction stress Shear stress fluxWater pressure D- value 1.3mm4.1mm767.8KPa578.7KPa390.5KPa1.334e- 7m/s 8.6mm Left-hole circumferential nodesK3+490 section vault monitor monitor

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3rd China-Japan Joint Seminar for the Graduate Students33 Fifth work step left hole circumferential nodes displacement contrast Non-coupling Coupling Fifth work step left hole vault displacement contrast Non-coupling Coupling Monitoring results

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3rd China-Japan Joint Seminar for the Graduate Students34 Nodes Non-couplingCoupling

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3rd China-Japan Joint Seminar for the Graduate Students35 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

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3rd China-Japan Joint Seminar for the Graduate Students36 Thank you for your kind attention Glimpses on seepage flow coupling problems a brief report by Li Peng

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