Pile foundations are deep foundations used when the site has a weak shallow bearing strata making it necessary to transfer load to a deeper strata either by friction or end bearing principles. Foundations provide support for structures by transferring the load to the rock or layers of soil that have sufficient bearing capacity and suitable settlement characteristics. There are a very wide range of foundations types available which are suitable for different applications. Foundations are classified mainly as Shallow foundations and Deep foundations.
Shallow foundations are used where the load imposed by a structure are low relative to bearing capacity of surface soils. Deep foundations are necessary where the bearing capacity of the surface soils is insufficient to support loads imposed on it and hence they are transferred to deeper layers with high bearing capacity.
Pile foundations are deep foundations which are formed by long slender columnar elements. They consist of two components: Pile cap and single or group of piles. Pile foundations are principally used to transfer the loads from super structure, through weak compressible strata or water on to stronger, more compact, less compressible and stiffer soil or rock. This type of foundation is used for large structures and also in situations where the soil is not suitable to prevent excessive settlement.