A cofferdam is a construction structure that retains water and soil that allows the enclosed place to be pumped out and excavated to be dry. Cofferdams are generally used for construction of bridge piers and new desist structures built within water.
Cofferdams are made by driving sheet piling, usually steel in militant works, into the bed to form a watertight fence. The vertical piles are held in area by horizontal framing members that are constructed of heavy timber, steel, or both of that materials . The sides of a cofferdam must be sturdy and well-braced to withstand the shock of being hit by a heavy weight of bucket; they must as well as be able to withstand the horizontal forces from the surrounding body of water into account the water inside is pumped from the cofferdam.
Types of cofferdams
- Braced cofferdams
- Cellular cofferdams
- Double-walled sheet pile cofferdams
A cofferdam can be constructed in almost any desirable shape. However, for practical and reasons of economy most cofferdams shapes are circular or rectangular.