Stability of Foundation Pits Protected by Coffer Dams

The footings and rafts are always placed below the ground level and trenches of foundation pits are prepared for housing them. Similar trenches are also excavated for the construction or placing of underground structures like utility lines, subways etc. by the cut and cover method. Depending on the soil properties of the construction site and depth of excavation, the sides of the excavations as well as the base of the excavation are protected with help of coffer dams. Generally for shallow depths of excavation and soil having medium strength, the design of the coffer dams need not be elaborate and design charts with high factor of safety can be used profitably.