In determining the external stability of retaining walls, failure modes like bearing failure,
sliding and overturning are normally considered in 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.
