What is a cofferdam

Cofferdams are utilized to dewater construction sites.  They are used to divert or contain water whenever working in the water requires dry conditions or less wave actions for personnel or equipment.

Uses of Cofferdams

Marine construction: working in water sometimes require dry or semi-dry conditions. water inflatable dams are a good alternative to other types of cofferdams. They have no adverse impact on the environment as they use the available water onsite, they are fast to deploy and fast to remove once the project is done. Water inflatable dams are inexpensive dams when compared to other cofferdams.  Working in creeks sometimes require two cofferdams to be deployed one downstream and one upstream to keep water from the construction site.

Water barriers against fast moving water:  Cofferdams are also used in river beds to slow down water flow. For this type of application, Water inflatable dams like FLEXIDAMS are anchored on the river bank and deployed upstream from the construction site.

There are different types of this chamber, and the difference is solely dependent on the purpose. Various construction materials are used differently, and this depends on the initial plan. However, regardless of the cofferdam structure and design, some of the following vital aspects affect the construction as well as the construction timing.

The first and the most important aspects are to determine how the water can go up in case of a flood and the velocity of water. These two aspects are some of the best guidelines while constructing a good cofferdam. The second aspect is the design. Different designs give a different kind of the final structure.

Cofferdam Shapes and Types

A cofferdam can be constructed in any shape. However, for economic reasons and practicalities, the most common cofferdam shapes are either circular or rectangular. Rectangular cofferdams, unlike circular cofferdams, are more common and are easier to construct.

There are mainly three types of cofferdams.

  • Braced cofferdams: Braced cofferdams are shaped from single sheet piles on the wall, which are then driven into the ground. These single-sheet piles then create a box-like shape around the excavation. After the sheet piles are driven to the ground, they are then braced and dewatered from the inside.
  • Double-walled cofferdams: Double-walled cofferdams are comprised of two parallel sheet pile rows that are driven to the ground. They are then connected with a system of tied rods on every level. The space left between the walls of the double-walled cofferdams is filled in with materials like sand, broken rock, or gravel.
  • Cellular cofferdams: Cellular cofferdams are not common and are only used when the excavation size bars the use of bracing.
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