Wonderful Engineering

Ever Wondered How Engineers Construct Structures Underwater? Here’s Your Answer

Have you ever wondered if engineers wanted to repair, let’s say a ship, how would they do that? No, they won’t drag the entire heavy ship to the land. No, they also would not go underwater in swimsuits carrying their tools and machinery in a backpack. So, what do they do? They build temporary, waterproof enclosures called cofferdams to carry out repair underwater.

Credits: Winona Daily News

This structure is built into the water basin and then all water is pumped out making way for a dry work space. According to geotechnical engineering, this construction is not as easy as lowering walls into the water floor. Engineers have to design a structure that is flood-proof and collapse-proof. These cofferdams are traditionally used in numerous structures of aqueous engineering.

Credits: interesting engineering

How to construct a cofferdam?

The engineers need to do a complete analysis of water table levels and soil layers first to make sure their structure has no seepage or uplift later when people begin work. Next, they have to lower interlocking piles into the floor of the water basin. For this, they need to first calculate the required depth of every pile lowered into the bed. Any miscalculation or fault in the design could mean flooding and collapse of the work area. When the structure is completed, the temporary cofferdams are removed and the structure is lowered in water.

Credits: U.S. Army Corps of Engineers

While repairing anchored ships, engineers again use cofferdams as a “dry dock”, separating the ship from water and repair it at the site of damage. This is the common repair method for huge ships that cannot be lifted and brought to land. For example, when a cruise ship is being expanded, the engineers will first build a coffer around it to remove water and then begin construction.

The cofferdams are not a cheap alternative to repair and construction underwater. Cofferdam, in fact, is used where it is the only construction option. Did you like the timelapse video of sheet pile cofferdam? Let us know in comments!