What is Caisson Foundation ?
A Caisson Foundation is a watertight retaining structure used as bridge pier in the construction of concrete dam, or for the repair of ships. Caisson Foundation is also known as Well foundation. They are build in such a way that the workspace is always kept dry by pumping out the water whenever necessary or filled with the help of muck tubes.
Types of Caisson Foundation
Box Caisson :
A box caisson is open at the top and closed at the bottom and is made of timber, reinforced concrete or steel. Such a type of Caisson foundation is used where bearing stratum is available at shallow depth and where loads are not heavy.
Open Caisson :
An open caisson is a box of timber, metal, reinforced concrete or masonry which is open both at the top and at the bottom. It is used for building and bridge foundations. The open caissons are also called as wells. The well foundation forms the most common type of deep foundation for bridges in India.
Pneumatic Caisson :
The pneumatic caissons are closed at the top and open at the bottom. The compressed air is used to remove the water from the working chamber at the bottom and the foundation work is thus carried out in dry conditions. The pneumatic caissons are useful where it is not possible to adopt the open caisson.
Pneumatic caissons are adopted where the depth of the water is more than 12 meters. The maximum depth of water upto which pneumatic caissons can be used is limited from the consideration of the health of the workers.