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
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
 Properties of each Joints
strength
 large number of joint sets
present in the slope
 Properties of each joint set or
combined properties
 Heavily jointed rock
 Properties of jointed rock mass
 Waste dump / very weak rock
/ soil
 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 joint
friction joint
joint normal stiffness
joint 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
2D Simulation by Geoslope
software based on Finite element
method
3D Simulation by Ansys 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
C
trial

trial

1
F
trial
C
 arctan 
1
F
trial
tan  
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
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Numerical Modeling