Driven pile foundations can be made from concrete, steel or timber. These piles are prefabricated before placing at the construction site. When driven piles are made of concrete, they are precast. These piles are driven using a pile hammer.
When these piles are driven into the granular soils, they displace the equal volume of soil. This helps in compaction of soil around the sides of piles and results in the densification of soil. The piles which compact the soil adjacent to it is also called as compaction pile. This compaction of soil increases its bearing capacity.
Saturated silty soils and cohesive soils have poor drainage capability. Thus these soils are not compacted when driven piles are drilled through it. The water have to be drained for the soil to be compacted. Thus stresses are developed adjacent to the piles have to be borne by pore water only. This results in increase in pore water pressure and decrease in bearing capacity of the soil.