The purpose of a cofferdam is to exclude water and/or soil from an area required for construction work, to a depth below the surface.
A cofferdam can be used for either permanent or temporary works and is commonly utilised in the construction of underground tanks, drainage, and structures built in water. Cofferdam walls are formed from sheet piles acting in cantilever or supported by walers, internal braces and external anchors.
Ivor King hold up to 3000 tonnes of steel sheet piles in stock, which can be used in temporary cofferdams. Typically for temporary works with excavations between 3 and 5 metres below ground level sheet piles will be installed, and braced internally with one level of temporary propping. This propping can either be formed of structural steel, fabricated and installed on site or a proprietary framing system can be supplied. Upon completion of the works, the steel sheet piles can be removed and brought back into our stock.
Cofferdams have numerous benefits when considered as part of a permanent works project such as a basement construction. Considerable savings in both time and money can be achieved by using the steel sheet pile as the structural wall whereby the wall can be designed to carry both horizontal and vertical loadings. Additionally, sealants and waterproofing details are used to make this permanent structure watertight.
Our design team will always consider the best option to suit your needs.
A cofferdam can be constructed in almost any desired shape. For practical and economic reasons, most cofferdams are either rectangular or circular. In general, circular cofferdams offer an advantage by providing a more open excavation over the entire plan area, when bracing is provided solely by ring beams. Installation of sheet piles in circular cofferdams requires stricter construction controls. Rectangular cofferdams are simpler to construct but typically require more complex internal bracing. For small scale cofferdams, and especially those that are for temporary works, it may be most economical to hire in a proprietary framing system.
Performing work over water adds complexity and additional engineering challenges and is more costly than performing work on land. When work is performed below water, the difficulties and cost difference can increase dramatically.
Key Benefits & Advantages of Cofferdams
- Can be constructed into any desirable shape
- Allows excavation and construction in otherwise poor working environments
- Enables safe working environment for team members to work
- Offers greater commercial flexibility - steel sheet piles can be easily installed and removed which allows for materials to be re-used.