What is the function of shear keys in the design of retaining walls?

A retaining wall can have following four types of failure mechanisms-

1. Compression
2. Tension
3. Sliding
4. Overturning

To prevent sliding failure, the only resistive force we have is friction. If sliding force is greater than friction force provided by the weight of the wall, we have to prevent it using a shear key.

However, in practice, it is common to provide a shear key even if there is no possibility of sliding failure.

Resistance to the shear forces

Shear key is a structure or a part used in footings of retaining waalls to resist the sliding of retaining walls. It is more better idea to resist the Slip. It is mostly good in seismic regions.

shear key in retaining walls to safey sliding

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 principle of shear keys is as follows:

The main purpose of 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.