INFINITE SLOPE ANALYSIS

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INFINITE SLOPE ANALYSIS

• THE SIMPLEST WAY TO MODEL LANDSLIDES!

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GREATER THE NORMAL FORCE THE GREATER THE
RESISTING FORCE
What is normal anyhow?
FRICTION AND COHESION
GRAVITY
NORMAL FORCE
3
AN EXAMPLE WHERE THE ASSUMPTIONS OF A PLANAR
SLOPE ARE WELL MET
4
Driving Force -- Gravity
Driving Force
h/cos ?
?
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MOHR-COULOMB FAILURE CRITERIA
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(No Transcript)
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Normal stress (kN/m2)
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Resisting Force -- Soil Strength
Resisting Force
h/cos ?
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Factor of Safety
F 1 Slope Stability
F 1 Slope Instability
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CLEARCUTTING AND LANDSLIDES
Slide scars
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Soil Strength Parameters(Selby, 1993)
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Effective Cohesion -- Vegetation Effects
from Selby, 1993
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?
100
Till
o

(c 150 kpa,
??
33.5
)
10
Sand
Factor of Safety
o

(c 1 kpa,
??
37
)
25o slope
1
35o slope
saturated
0.75 m slab
0.1
0
4
8
12
Effective Root Cohesion (kPa)
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Mechanics of Deforestation-Induced Erosion

• Removal of trees suppression of vegetation by
  grazing
• Roots root or stumps are pulled
• Cohesion ??????in two to five years
• Greatest effect on steep, sandy slopes
• Consistent with geologic observations