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Cofferdam structures

 Cofferdams are temporary structures used as a barrier to keep out the water and soil during the construction of a permanent structure such as a foundation in a maritime environment. The loads imposed on cofferdams structure includes hydrostatic forces of the water and dynamic forces due to waves and currents. The construction of cofferdams is a tough job since it is usually constructed offshore and in severe weather conditions. Therefore, the tolerance of construction may deviate from the design due to construction conditions, and cofferdams elements may deform significantly during cofferdam construction. 

Figure 1

For a typical cofferdam, the construction sequence will be as follow.
  • The construction of the cofferdam will begin with the preparation of the cofferdam area. The soil and sediments will be removed, and the area will be leveled. 
  • The temporary support piles will be driven, and temporary supporting frames will be erected on support piles. 
Figure 2

  • Drive the sheet pile to grade, Block between bracing frame and sheets, and provide ties for sheet piles at the top as necessary.
  • The next step is to excavate up to grade or slightly below the grade. Then driving the bearing piles. Then place the rock fill to level and support the cofferdam area. 
Figure 3

  • The concrete will be poured into the trench to provide support for the cofferdam and to provide a seal between the cofferdam and the bedrock. Then the dewatering of water can start. Once the water is dewatered, the construction of a new structure can begin. 
Figure 4

 The use of cofferdams will facilitate the construction of structures underwater. Cofferdams will eliminate the difficulties of constructing a structure in the sea. The advantages of cofferdam are:
  • Allow excavation and construction of structures in a poor environment 
  •  Provides a safe environment to work
  •  Steel sheet piles are easily installed and removed.
  •  Materials can typically be re-used on other projects.


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