Cofferdams: Definition, Requirements, and Uses | Civil Engineering Notes

✅ What is a Cofferdam?

A cofferdam is a temporary structure built to remove water and/or soil from a specific area so that construction work can be carried out in dry conditions. It is commonly used in the construction of bridges, dams, and other hydraulic structures.

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⚙️ Requirements of a Cofferdam:

1️⃣ Reasonable Watertightness:

It should be reasonably watertight.It may rest on impervious soil or reach impervious strata through pervious soils. If needed, a concrete layer can be placed at the base and allowed to harden before pumping water.

2️⃣ Absolute Watertightness Not Essential:

100% watertightness is costly and often impractical. Design should aim to minimize construction and pumping costs.

3️⃣ Designed for Maximum Stability:

Must withstand maximum water levels and forces. Should resist bursting, overturning, and sliding.

4️⃣ Exclusion of Ground or Surface Water:

Can handle both groundwater and surface water. Effective for shallow or deep, still or running water.

5️⃣ Construction Materials:

Common materials include earth, timber, steel, and concrete.

6️⃣ Site Construction:

Typically constructed directly at the site of work.

7️⃣ Adaptability:

Construction type depends on water depth, soil conditions, material availability, and water level changes.

8️⃣ Cost-Effective for Large Areas:

Most useful when enclosing large areas with a reasonably shallow hard bed.

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🛠️ Uses of Cofferdams:

1️⃣ To assist in pile driving operations.
2️⃣ To place grillage and raft foundations.
3️⃣ To build foundations for piers, abutments of bridges, dams, and locks.
4️⃣ To enclose areas for removal of sunken vessels.

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📝 Conclusion:

Cofferdams are crucial in civil engineering where underwater construction is required. Their proper planning and design ensure safety, reduce construction time, and optimize cost.