Question

Which of the following are the general design requirements of retaining wall?

1. The factor of safety against sliding should be at least 1.5

2. The factor of safety against over-turning should be at least 2.0

3. The bearing pressure at toe should be less than the bearing capacity of the soil

4. The length of retaining wall to be cast in one go should not exceed 10 m otherwise cracks may develop 

1. 1, 2 and 3 only
2. 1, 3 and 4 only
3. 1, 2 and 4 only
4. 2, 3 and 4 only

Answer 1

Correct Answer - Option 1 : 1, 2 and 3 only

Concept:

As per IS 14458 (Part-2): 1997, Cl: 5.2, retaining wall for hill area, the following are the design requirements.

1. Retaining wall shall be designed as rigid wall.

2. The minimum value of factor of safety against overturning and sliding are 2 and 1.5 respectively in case of static loads. However, these values are 1.5 and 1 respectively when subjected to earthquake forces.

3. The maximum base pressure at toes shall be less than the allowable bearing capacity of soil, but it shall be increased by 33% in case of earthquake forces.

4. The minimum base pressure recommended is zero.

5. The minimum factor of safety against floatation is 1.25.

Note:

There is no direct recommendation regarding the length of retaining wall. However, the length of retaining wall is restricted to 8 m as per Cl 5.4 as it is not possible to construct wall throughout the entire length of road.