It is not uncommon that granular fill layers and rockfill layers are placed beneath the bottom of concrete retaining walls. The purpose of such provision is to spread the loading in view of insufficient bearing capacity of foundation material to sustain the loads of retaining walls. Upon placing of granular fill layers and rockfill layers, the same imposed loads are supported by a larger area of founding material and hence the stress exerted by loads is reduced accordingly.
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Layers of granular fill and rockfill materials are not standard details of concrete retaining wall. If we are fully satisfied that the founding material could support the loads arising from retaining walls, it is not necessary to provide these layers of granular fill and rockfill materials.
This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.
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