Question

If the lateral pressure on a retaining wall is high, the following measure are taken while designing:
1. Wall thickness is increased to resist the moment at base
2. Slab thickness is increased to resist the moment
3. Height of the retaining wall to be increased to increase the moment resisting capacity
4. Shear key is provided to resist the lateral pressure

Answer 1

Correct Answer - Option 4 : Shear key is provided to resist the lateral pressure

Explanation:

• In determining the external stability of retaining walls, failure modes like bearing failure, sliding, and overturning are normally considered in the design.
• In considering the criterion of sliding, the sliding resistance of retaining walls is derived from the base friction between the wall base, and the foundation soils. To increase the sliding resistance of retaining walls, other than providing a large self-weight or a large retained soil mass, shear keys are to be installed at the wall base.
• The main purpose of the installation of shear keys is to increase the extra passive resistance developed by the height of shear keys. However, active pressure developed by shear keys also increases simultaneously.
• The success of shear keys lies in the fact that the increase of passive pressure exceeds the increase in active pressure, resulting in a net improvement of sliding resistance.