Open Caisson

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Definition - What does Open Caisson mean?

An open caisson is a hollow structure with both an open top and bottom that is designed to keep water out of a construction zone. It is one of three caisson shaft types, which also include pneumatic and box caissons. Open caissons are used in trenchless operations, such as in the excavation of entrance or exit pits.

Trenchlesspedia explains Open Caisson

Water can cause major problems during underground excavation. When drilling below the water table or below bodies of water, construction engineers must devise ways to keep water out of the construction site. One way is to use watertight retaining structures called caissons. These are often used in the construction of bridges, but they are also useful in the trenchless construction industry.

Open caissons are often used in soft soil. A caisson may be made of wood, steel or concrete. An open caisson used to penetrate the soil must be strong enough to withstand pressure from any hydraulic jacks that may be used to force it downward into the ground. Soil excavated from the bottom of the caisson is transported out the top for disposal. Once the excavation is complete, the caisson may also become integrated into the final construction.

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