A cofferdam is a temporary structure , which is constructed to remove water or exclude water from an area of excavation , either ground water or water laying above ground level , and make it possible to carry out the construction work under reasonably dry conditions.
The cofferdams are constructed to facilitate pile driving operations.
It is used to place grillage & raft fondations., and when the foundations for piers and abutments of a bridge , dams etc. are to be constructed.
It is constructed to provide working platform for the fondations of buildings , when the water is met with. and constructed to enclose a space for the removal of sunken vessels.
Types of Cofferdams :-
1. Earth fill cofferdams.
2. Rock fill cofferdams.
3. Sand bag dike cofferdams.
4. Timber crib or Rock filled crib cofferdams.
5. Sheet pile cofferdams.
6. Single wall cofferdams
7. Double wall cofferdams.
8. Cellular cofferdams.
9. Movable or suspended cofferdams.