Limit equilibrium Method (LEM)

Advantage of LEM

Limitation of LEM

Numerical modeling

Advantage

Limitation

STABILITY ANALYSIS OF SLOPE

Software based on Limit equilibrium Method

SLIDE (rocscience group)

GALENA

GEO-SLOPE

GEO5

GGU

SOILVISION

Software based on Numerical modeling

PHASES2

PLAXIS

FLAC-SLOPE / UDEC / PPF

ANSYS

FEFLOW

GEOSLOPE/SIGMA

SOIL-VISION

Required input properties

Young modulus

Poisson ratio

Density

Failure criterion:

M-C H-B

Cohesion UCS

Friction angle m & s

Numerical modeling

Type of failure mechanism

Physico-mechanical behaviour of slope material

Types of analysis

Numerical modeling

• Continuum modelling FEM, BEM and FDM

• Discontinuum modelling

DEM, UDEC

• Hybrid modelling PPF,

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

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

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

Continuum modelling

• Typical Input required

Moduls of Elasticity

Poision ratio

Density

Shear strength

(cohesion and friction angle)

Model Behavior

Continuum modelling

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

• Continuum modelling (water simulation)

Pore water pressure

Ground water table

Infiltration of rain water

Discontinuum modelling

Discontinuum modeling 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

Discontinuum modelling

Discontinuum modelling

cohesion joint dilation jointfriction jointjoint normal stiffnessjoint shear stiffness

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;

Important considerations

Two-dimensional analysis versus three-dimensional analysis

3D Simulation by Ansys software based on Finite element method

2D Simulation by Geoslope software based on Finite element method

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

Selecting appropriate zone size

Different view discritized view of internal dump slope

Boundary conditions

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

Water pressure

Simulation of rain water infiltration and generation of water table

Excavation sequence

Show the sequential excavation

Stability / failure indicators

Factor of safety

Displacement ( x and Y)

Shear Strain

Yield Points

Plastic Points

unbalance force/ convergence of solution

Velocity

Stability / failure indicators

Factor of safety

CF

C trialtrial 1

tan1arctantrial

trial

F

Stability / failure indicators

Displacement ( x and Y)

Stability / failure indicators

Shear Strain

Stability / failure indicators

Yield Points

Stability / failure indicators

Velocity Vector

Stability / failure indicators

unbalance force/ convergence of solution