A pile is basically a long cylinder of a strong material such as concrete that is pushed into the ground to act as a steady support for structures built on top of it. Pile foundation has many applications as will be explained below.
In foundation practices, the main point of concern is bearing capacity of soil. Bearing capacity can be defined as the maximum load that can be carried by the soil strata. When the soil is strong enough that it can carry the whole load coming on it, then we use shallow foundation. Shallow foundations are usually used where hard soil strata is available at such a depth that construction of foundation is not too costly.
If hard soil is available at deeper levels of earth, then there is a need of some source that can transfer the load of the structures on the deep hard soil strata. This source can be said to be as the deep foundation. Pile foundation is a type of foundation in which pile is usually used as the source to transfer the load to deep soil levels. Piles are long and slender members that transfer the load to hard soil ignoring the soil of low bearing capacity. Transfer of load depends on capacity of pile. There is a need that pile should be strong enough to transfer the whole load coming on it to underlying hard strata. For this purpose, pile design is usually given much consideration. Depending on the load, type of material is usually selected for the piles.