Position of Shear Keys

Question

Which is the best position of shear keys underneath retaining walls?

Answer 1

Installation of Shear Keys increases the sliding resistance of retaining walls without the need to broaden their base. The effect of shears keys improves the deepening failure of soil plane locally at the keys. The increased sliding resistance arises from the difference between the passive and active forces at the sides of keys. In situation, weak soils are encountered at the base level of shear keys, the failure planes all along the base of retaining walls because of sliding, may be shifted down to base level of the keys.

Shear keys are usually designed not to be placed at the front of retaining wall footing base because of likely removal of the soils by excavation and subsequently the lateral resistance of soils can hardly be mobilized for proper functioning of shear keys. For shear keys located at the back of footings, it poses a potential benefit that higher passive pressures can be mobilized due to higher vertical pressure on top of the passive soils.