Pier Foundations
Pier foundations are adopted when buildings are subjected to heavy loads, and have to be located either in a soft or sandy soil which is overlying above a hard rock at certain depth. The pier foundations are used to transmit the heavy loads that are imposed on buildings to the hard rock below.
The construction method of pier foundation involves sinking of vertical shafts up to hard rock bed and filling the shafts with concrete. The diameter of the shaft and their centre to centre spacing depend upon the loading condition, nature of soil and depth at which the hard bed is situated. However, in no case the diameter or the least horizontal dimension (in case of square or rectangular pier) of plain concrete pier should be less than 1/12th its height. To prevent the side earth from falling in, the inside of the shaft is sometimes lined with timber. The timber lining is removed during the filling up of the shaft with concrete. The shafts are connected to each other by a reinforced cement concrete or steel grillage cap. Concrete cap is sometimes built in the form of arch.