Which of these factors will affect the shear strength of material on a slope? (c

Question

Which of these factors will affect the shear strength of material on a slope? (choose all that apply)

rock type

cohesion of sediments

strength of gravity

the orientation of bedding or metamorphic layers

angle of the slope

amount of water the material contains

Which of these are potential triggers for mass wasting events? (choose all that apply)

heavy rain

earthquake

reduction in slope angle

lithification of sediment into solid rock

shaking from construction or mining

freezing and thawing

rapid melting of snow or ice

Explanation / Answer

1. Question: Which of these factors will affect the shear strength of material on a slope?

Answer:

1. Strength of gravity.

2. Angle of the slope.

3. Amount of water the material contains.

Explanation: Basically on a slope, the force of gravity can be resolved into two components (one acting perpendicular to the slope, one acting tangential to the slope). This is the reason why down-slope movement is favoured by steeper slope angles which increase shear strength. When shear force becomes greater than shear strength, then slope failure will occur. WATER plays an important role in mass movement processes, because generally water do have the ability to change the angle of repose.

2. Question: Amount of water the material contains which of these are potential triggers for mass wasting events?

Answer:

1. Heavy rain.

2. Earthquake.

3. Reduction in slope angle.

4. Rapid melting of snow or ice.

5. Shaking from construction or mining.

Explanation: Mass wasting is the downslope movement of soil and rock. The main force responsible for Mass movement is GRAVITY. When the downward pull of gravity overcomes the forces resisting it, then mass movements can occur. Mass wasting happens because of tectonic processes that have created uplift. Removal of rocks low down on a hill will destabilize rocks higher up by MINING procedures and can contribute to mass wasting. Natural disasters such as earthquakes, heavy rains, volcanoes and land slides are major triggers for mass wasting events. Apart from these factors, addition of water from rainfall or snow melt do add weight to the slope and as the stress increases, this can lead to slope instability and finally result in mass wasting.

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