- 2078 Bhadra · 2 marks
Cellular cofferdam
Short answer
A cofferdam is a temporary enclosure pumped dry for underwater construction. A cellular cofferdam consists of interconnected steel sheet pile cells filled with granular soil, forming a self-supporting gravity wall. It resists water pressure by its own weight, eliminating internal bracing, and is used for piers, locks, and dams in deep water.
Define cofferdam and explain the cellular cofferdam with the help of a neat sketch.
A cofferdam is a temporary enclosure built in water or water-bearing ground, pumped dry to allow construction below water level.
A cellular cofferdam consists of a row of connected cells made of interlocking flat-web steel sheet piles, filled with sand, gravel or rock fill. Cells may be circular, diaphragm (arcs with cross walls) or cloverleaf.
Plan: ( )( )( )( ) Section: | fill |
circular cells | | ~~~ water
joined by connecting arcs |______| (dry on right)
- The sheet piles act in tension (ring tension) and hold the fill; the filled cell behaves as a gravity wall resisting water pressure by its own weight.
- It is self-supporting, so no internal bracing blocks the working area.
- Stability is checked for sliding, overturning, interlock tension (hoop tension ), shear along the centre line of the cell, and bearing.
- Uses: piers, locks, dams, deep water work; reusable and quick.
✓ Answer checked by Claude Sonnet 5.5