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Cofferdams allow engineers to displace water to allow for construction operations.

 

When a construction plan involves building across or within a waterway, an engineer has a choice: either work under water, or move the water. Since working under water is generally not logistically or economically feasible, the solution is often to use a cofferdam to displace water from the construction zone.

The cofferdam is a temporary structure, usually built in place, and tight enough so that the water can be pumped out of the structure and kept out while construction on the foundations is in progress. Common cofferdam types are earthen, steel sheeting, wooden sheathing, and crib.. Steel is commonly used for cofferdam construction. Sheet piling is manufactured in many interlocking designs and in many weights and shapes for varying load conditions. The piling is driven as sheeting in a row to forma relatively tight structure surrounding the construction area. This pile wall is supported in several ways. It may be supported by a framework of stringers and struts. A cofferdam wall can consist of a double row of piles tied together with heavy steel ties and filled with earth. This can square, rectangular, circular, or oval shape for stability around the construction area. Wooden sheathing, instead of steel, is similarly used in cofferdam constructions. Interlocking timber sheathing is driven as a single wall and supported by stringers and cross struts between walls, or it is driven in double rows as a wall. The sheathing in each row is connected and tied with braces.

       
   
 
       

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