Well foundation | Types of Caisson

Well Foundation

A cassion may remain defined as a watertight structure made up of wood, steel approximately reinforced concrete, constructed in connection with excavation for the foundation of bridges, piers. abutments into a river, lake, etc

Types of Caisson

1. Open caisson
2. Box caisson
3. Pneumatic caisson

Open Caissons

• That is a box-type from the structure which is open at the head including at the bottom. Open caisson is normally used on sandy soils or soft bearing stratum and where no firm bed is available at a higher depth.

According to upon the shape of caissons, open caissons container be further categorised into three types as,

1. Open caisson
2. Single-wall open caisson
3. Cylindrical open caisson
4. Open caisson with dredging wells.

• It is the caisson where it's top and bottom ends are open and the central space filled with sand.

Box Caisson 

• This type of caisson is similar to the open caisson except that it is closed at the bottom.
• The cassion is cast and cured on land and when required, it is launched in the water and towed to the site for sinking.
• The cassion is sunk by filling sand, gravel or concrete in the empty space inside.
• Space, where the empty cassion is to be placed, must be levelled.

Pneumatic Caisson

• This type of cassion is closed at the top and open during construction at the bottom.
• The water is excluded from the cassion chamber by the compressed air.
• In this cassion, the working chamber and shaft are made airtight.
• So that workmen may take out excavation work underneath and water may not enter inside from below.
• Each cassion has two airlocks, one for workmen go down for working and another for the material is taken out.