1. INFINITE SLOPE ANALYSIS THE SIMPLEST WAY TO MODEL LANDSLIDES!

2. GRAVITY FRICTION AND COHESION NORMAL FORCE GREATER THE NORMAL FORCE THE GREATER THE RESISTING FORCE What is normal anyhow?

3. AN EXAMPLE WHERE THE ASSUMPTIONS OF A PLANAR SLOPE ARE WELL MET

4. Driving Force -- Gravity Driving Force  h/cos 

5. MOHR-COULOMB FAILURE CRITERIA

7. Normal stress (kN/m 2 )

8. Resisting Force -- Soil Strength  Resisting Force h/cos 

9. Factor of Safety F ≤ 1Slope Instability F ≥ 1Slope Stability

10. CLEARCUTTING AND LANDSLIDES Slide scars

11. Soil Strength Parameters (Selby, 1993)

12. Effective Cohesion -- Vegetation Effects from Selby, 1993

13.  0.1 1 10 100 04812 Factor of Safety Effective Root Cohesion (kPa) Till Sand (c = 1 kpa,  = 37 o ) (c = 150 kpa,  = 33.5 o ) saturated 0.75 m slab 35 o slope 25 o slope

14. 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