Piles are used to take the weight o

Piles are used to take the weight of a building when it is impossible to dig down a solid layer of earth, either because the ground is water-logged or because there is a very great depth of poor soil
Piles are solid lengths of timber, steel, or reinforced concrete, generally from 20 to 80 feet long driven into the ground by a heavy steam hammer
sometimes hollow steel tubes are used, being driven into the ground in the same way solid piles and afterwards filled with concrete