6.2 - Slope stability

Question 1

Translational slope failure

Answer 1

Failure of slope along a weak zone of soil

Question 2

Rotational slope failure

Answer 2

The failure surface may be almost circular, passing under the slope toe and occur sin cohesive soils

Question 3

Key factors that may cause slope failures

Answer 3

Conditioning factors and triggering factors

Question 4

Conditioning factors

Answer 4

• Stratigraphy and lithology
• Geological structure
• Hydro geological conditions and behavior of materials
• physical, strength, and deformational properties
• In situ stresses and state of stress

Question 5

Triggering factors

Answer 5

• Static overloads
• Dynamic loads
• Changes in hydrogeological conditions
• Climatic factors
• Changes in slope geometry
• Reduction of strength properties

Question 6

Rock slope stability vs soil stability

Answer 6

The stress strain behavior of each material (and therefore its stability) is governed by its strength properties, which also depend on the presence of water.

Question 7

Why is water the cause of most slope failures?

Answer 7

The presence of water in a slope reduces stability by decreasing the ground strength and increasing forces that favor instability by:
- Reducing the shear strength as effective stress DECREASES
- Increasing the weight of material (with increasing saturation)
- Softening soils with increasing water content
- Internal erosion (piping)
- Physical and chemical weathering
- Freezing water between discontinuitues