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Limit equilibrium Method (LEM) Advantage of LEM Limitation of LEM

STABILITY ANALYSIS OF SLOPE. Limit equilibrium Method (LEM) Advantage of LEM Limitation of LEM Numerical modeling Advantage Limitation . Software based on Limit equilibrium Method SLIDE ( rocscience group) GALENA GEO-SLOPE GEO5

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Limit equilibrium Method (LEM) Advantage of LEM Limitation of LEM

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  1. STABILITY ANALYSIS OF SLOPE Limit equilibrium Method (LEM) Advantage of LEM Limitation of LEM Numerical modeling Advantage Limitation

  2. Software based on Limit equilibrium Method SLIDE (rocscience group) GALENA GEO-SLOPE GEO5 GGU SOILVISION

  3. Software based on Numerical modeling PHASES2 PLAXIS FLAC-SLOPE / UDEC / PPF ANSYS FEFLOW GEOSLOPE/SIGMA SOIL-VISION

  4. Required input properties Young modulus Poisson ratio Density Failure criterion: M-C H-B Cohesion UCS Friction angle m & s

  5. Numerical modeling • Type of failure mechanism • Physico-mechanical behaviour of slope material • Types of analysis

  6. Numerical modeling • Continuum modelling FEM, BEM and FDM • Discontinuum modelling DEM, UDEC • Hybrid modelling PPF,

  7. What are the conditions of slope in the field • Simple slope with single, two or three joints • Large number of joint sets present in the slope • Heavily jointed rock slope • Waste dump / very weak rock / soil

  8. Simple slope with single, two or three joints • large number of joint sets present in the slope • Heavily jointed rock • Waste dump / very weak rock / soil • Properties of each Joints strength • Properties of each joint set or combined properties • Properties of jointed rock mass • Properties of waste rock

  9. Continuum modelling Continuum modeling is best suited for the analysis of slopes that are comprised of massive, intact rock, weak rocks, and soil-like or heavily jointed rock masses. Discontinuum modeling is appropriate for slopes controlled by discontinuity behaviour. • Critical Parameters: shear strength of material, constitutive criteria, water condition, insitu stress state • Advantages: Allows for material deformation and failure, model complex behaviour, pore pressures, creep deformation and/or dynamic loading can be simulated • Limitations: inability to model effects of highly jointed rock

  10. Continuum modelling • Typical Input required Moduls of Elasticity Poision ratio Density Shear strength (cohesion and friction angle) Model Behavior

  11. Continuum modelling

  12. Typical Input required • Moduls of Elasticity for rock and joints • Poision ratio for rock and joints • Density • Shear strength for rock and joints • Joint behaviour • Water pressure

  13. • Continuum modelling (water simulation) Pore water pressure Ground water table Infiltration of rain water

  14. Discontinuum modelling • Discontinuummodeling is appropriate for slopes controlled by discontinuity behaviour • Critical Parameters: discontinuity stiffness and shear strength; groundwater characteristics; in situ stress state. • Advantages: Allows for block deformation and movement of blocks relative to each other, can modeled with combined material and discontinuity behaviour coupled with hydro - mechanical and dynamic analysis • Limitations: need to simulate representative discontinuity geometry (spacing, persistence, etc.); limited data on joint properties available

  15. Discontinuum modelling

  16. Discontinuum modelling

  17. cohesion joint dilation joint friction joint joint normal stiffness joint shear stiffness

  18. Hybrid modelling Hybrid codes involve the coupling of these two techniques (i.e. continuum and discontinuum) to maximize their key advantages. • Critical Parameters: Combination of input parameters • Advantages: Coupled finite-/distinctelement models able to simulate intact fracture propagation and fragmentation of jointed and bedded rock. • Limitations: high memory capacity;

  19. Important considerations

  20. Two-dimensional analysis versus three-dimensional analysis 2D Simulation by Geoslope software based on Finite element method 3D Simulation by Ansys software based on Finite element method

  21. Continuum versus discontinum models 2D simulation of bench slope by FLAC based on finite difference method 3D simulation of slope 3DEC software based on discontinum modeling

  22. Selecting appropriate zone size Different view discritized view of internal dump slope

  23. Boundary conditions Typical recommendations for locations of artificial far-field boundaries in slope stability analyses.

  24. Water pressure Simulation of rain water infiltration and generation of water table

  25. Excavation sequence Show the sequential excavation

  26. Stability / failure indicators Factor of safety Displacement ( x and Y) Shear Strain Yield Points Plastic Points unbalance force/ convergence of solution Velocity

  27. Stability / failure indicators Factor of safety

  28. Stability / failure indicators Displacement ( x and Y)

  29. Stability / failure indicators Shear Strain

  30. Stability / failure indicators Yield Points

  31. Stability / failure indicators Velocity Vector

  32. Stability / failure indicators unbalance force/ convergence of solution

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