Caissons are mainly used for the deep foundation located below water where foundation is expanded up to or underneath the river bed in order to retain the perfect durability.

Caissons are built up in terms of excavation for the foundation of piers and abutments in rivers and lake, bridges, break water dock structures toward safeguarding of shore, lamp house etc.

If it is required to build up well foundation under water, development caisson is a good choice.

The caisson structure is effective in case the depth of water in river, lake or sea is high.

Caisson are generally utilized as foundation for bridge piers, abutments in rivers, seas, lakes, break waters and other shore construction works.

It is also suitable for pump house where extreme vertical and horizontal forces operate.

It is sometimes applied for large and multi-storied building other structures.

The caissons are categorized as follow:-

• Open caisson
• Box caisson
• Pneumatic caisson

Open caisson

It belongs to a box type of structure that is open at the top and at the bottom. Open caisson is generally utilized on sand soils or soft bearing stratum where no rigid bed exists at a greater depth.

Based on the shape of caissons, open caisson is classified as follow:-

• Open Caisson
• Single Wall Open Caisson
• Cylindrical Open Caisson
• Open Caisson with dredging wells

Construction Method of Open Caissons

If dry conditions can’t be done on the job site, then caisson is produced in barges or slipways.

Then, it is pulled to its final position by floating.

Guide piles are usually applied for plunging the first few lifts.

Plunging of caissons is directly performed in open water.

Benefits of open caissons

• It can be expanded up to greater depths.
• Construction cost is considerably low on bed level or lower side.

Box caissons

1. It has similarity with open caisson, the basic discrepancy is that it is closed at the bottom.
2. It is cast and cured perfectly on ground and then it is put in the water by stuffing the void spaces with sand or gravel or concrete.

Pneumatic Caissons

1. It is open at the bottom and close at the top.
2. It is particularly utilized at the place where it is complicated to build up the well.
3. It is perfect for the depth of water over 12 m.
4. While developing pneumatic caisson, the water is eliminated from the working chamber by compressing air and the foundation work is done in dry condition.
5. It is built up with timber, concrete or steel.