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INFINITE SLOPE ANALYSIS. THE SIMPLEST WAY TO MODEL LANDSLIDES!. GREATER THE NORMAL FORCE THE GREATER THE RESISTING FORCE. What is normal anyhow?. FRICTION AND COHESION. GRAVITY. NORMAL FORCE. AN EXAMPLE WHERE THE ASSUMPTIONS OF A PLANAR SLOPE ARE WELL MET. Driving Force -- Gravity.
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INFINITE SLOPE ANALYSIS THE SIMPLEST WAY TO MODEL LANDSLIDES!
GREATER THE NORMAL FORCE THE GREATER THE RESISTING FORCE What is normal anyhow? FRICTION AND COHESION GRAVITY NORMAL FORCE
AN EXAMPLE WHERE THE ASSUMPTIONS OF A PLANAR SLOPE ARE WELL MET
Driving Force -- Gravity Driving Force h/cos
Resisting Force -- Soil Strength Resisting Force h/cos
Factor of Safety F ≥ 1 Slope Stability F ≤ 1 Slope Instability
Slide scars CLEARCUTTING AND LANDSLIDES
Effective Cohesion -- Vegetation Effects from Selby, 1993
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)
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