SCI261- topic 7 (mass wasting)

What is shear stress caused by?

downslope pull tending to cause movements

What is shear strength caused by?

•friction

•counteracts shearing stress

When does sliding occur?

when shearing stress exceeds

→frictional resistance

→or the shear strength of the material

What gradient of slope has a higher likelihood of slope failure?

the steeper the slope and the greater the shearing stress

What is the angle of repose?

the maximum slope angle at which the material is stable

How does the addition of water affect slope stability?

decreases

How does the addition or removal of vegetation affect slope stability?

may cause an increases in landslide activity

What is used to classify the different types of slope failure?

•sliding may occur along planes of weakness in the bedrock itself

•sliding may occur in unconsolidated material (loose sediments or soil)

What caused the Vaoint Dam landslide?

heavy rains

What are the different mitigation techniques used to reduce the risk of slope failure?

1. Slope reduction

2. Retention structures

3. Creating terraces

Slide vs slump

•Slide: Occur when a fairly cohesive unit of rock or soil slips downward along a clearly defined surface or plane

•Slumps: Can occur in rock or soil // Downslope movement of material that is typically accompanied by rotational movement // A scarp may be formed at the top of the slump

Mudflow vs debris flow

•Mudflow: movement of saturated soil // Volcanic lahars are mudflows

•debris flow: involving a wide variety of materials together in a single flow