Cofferdam refers to the temporary enclosure structure built for the construction of permanent water conservancy facilities in the construction of water conservancy projects.
Its function is to prevent water and soil from entering the construction site of the building, so as to drain the water in the cofferdam, excavate the foundation pit and build the building.
Generally, it is mainly used in hydraulic construction. Cofferdams are generally removed after use, except as part of formal buildings. The height of cofferdam is higher than the highest water level that may occur during construction.
Cofferdam, an earth embankment with trapezoidal cross section made of earth piles. The slope facing the water surface should not be steeper than 1:2 (aspect ratio, the same below), and the slope of foundation pit should not be steeper than 1: 1.5. Generally, it is filled with sandy clay.
The earth cofferdam is only suitable for shallow water, and the flow rate is slow, and the bottom of the cofferdam is impervious to water and soil. In order to prevent the slope facing the water surface from being eroded, sheets, turf or straw bags are often used to fill the fence. Rock-fill cofferdam can also be made in the rock-producing area, but the outer slope is covered with soil to prevent water leakage.