Raft or Mat Foundation and Well Foundation

Raft or Mat Foundation :

In the made-up ground, soft clay, etc. where the bearing capacity of the soil is very low and simple spread foundation is not economical, Raft or Mat foundation is provided. It consists of thick reinforced concrete slab covering the entire foundation area. Sometimes foundation beams are cast monolithically with the slab to carry excessive loads of columns.

Well Foundation :

This type of foundation is usually adopted in the construction of bridges and long-span culverts or where the soil is soft and sandy, generally in water. Well, foundations are made of masonry or concrete. It is also called caisson. A special cutting edge and a curb are laid on the ground and masonry built over it. The soil within the hollow inside and underneath the edges is excavated. This well sinks under its own weight or may be loaded. When well rests on sufficient hard strata; it is plugged concrete at top and bottom. If more then one well are excavated, these are connected by covering them with a continuous cap.