Q. Granular fill or rock fill essential at the base of concrete retaining walls?
It isn't uncommon that rock fill layers and granular fill layers are placed beneath the bottom of concrete retaining walls. Purpose of such provision is to spread the loading in view of insufficient bearing capacity of foundation material to maintain the loads of retaining walls.
Upon placing of rockfill layers and granular fill layers, same imposed loads are supported by a larger area of founding material and therefore stress exerted by loads is decreased accordingly.
Layers of rockfill and granular fill materials aren't standard details of concrete retaining wall. If we are fully satisfied that founding material could support the loads arising from retaining walls, it isn't essential to provide these layers of rockfill and granular fill materials.