Question

1. Briefly describe mass wasting.

2. How is mass wasting classified and provided names for different types of mass movements.

3. A cubical block with volume of 1 m3 and mass of 10 kg rests on a slope of 10 degree. The coefficient of friction is 0.4. Calculate the shear stress and shear resistance.

4. Why is it important to provide outlets (drainage) for water stored behind the retaining walls?

5. Discuss some methods of preventing slope failures in civil engineering projects. Support your answers with pictures.

Answer 1

Mass Wasting-:

It is basically a geomorphic process in which soil and rock mass move down the slope under the force of gravity.

In broad category, this term is used to represent the processes whereby the earth's surface materials are pulled down on a slope by the force of gravity.

It is also called mass movement.

Classification of mass wasting

Basically it is classified in to two classes-:

Flows --> The material behaves as a fluid.

e.g) Soil creep, earthflows, and mudflows

Slides The material behaves as a rigid solid that detaches along a basal surface.

e.g.) Slumps and landslides

Soln)

Volume of cubical block = 1m3

---> Side of block = 1 m

Shear force (fs) = fg x sin

= mg x sin

= 10 x 9.81x sin(10)

= 17.034 N

Shear stress = fs / A

= 17.034 / 1

= 17.034 N/m2

At rest condition

Shear resistance = shear force

= 17.034 N/m2

Importance to provide outlets (drainage)

When water accumulates behind a retaining wall, the lateral forces acting on the wall increase. The more water that has collected behind a retaining wall, the greater the hydrostatic pressure on the wall will be. If the overturning moment (caused by the total lateral forces) exceeds the resisting moment (caused by the total vertical forces), the wall will fail.

Hence ii is mportant to provide outlets (drainage) for water stored behind the retaining walls.

Methods of preventing slope failures

Some of the methods to prevent slope failure are given below -:

1) BiotechnicalBislope stabilization (By letting plants and vegetation stabilize a slope)

2) Terracing and Benching (dividing steep slopes in to smaller and less steep slopes)

3) Retaining wall (stablise the slope)

4) Friction piles (slope stabilization is done)

5) sheet pilling, rockbolt , shotcrete etc