Le Havre, France

During the construction of a new harbour in Le Havre (France), grout blocks adhered to the diaphragm wall at a depth of 22 metres.

DUC came up with a creative solution to remove the blocks that was faster and safer than the original method.

The intention was to use a chain connected to two winches mounted above the work to ‘saw’ the blocks away from the wall. To do this, local divers had to cut grooves in the bottom of the blocks through which the cable could pass.

Using explosives to cut the grooves would have been very time consuming. Therefore, DUC Marine Group was asked if a quicker method was available. As the blocks were made of a fairly hard material, DUC suggested to use our 2500 Bar high-pressure water jet to cut the initial grooves for the cable that would be used to saw through the blocks.

However, the cable ‘saw’ continually broke and little progress was made.

DUC provided the solution of using the water jet to make a 100 x 100 x 10 cm opening between the diaphragm wall and the block from above. A 68-tonne air bag was then positioned in this opening that was then inflated to force the grout block from the wall.

This resulted in the safe removal of the 15 to 45-tonne blocks. The job was concluded to the satisfaction of the client, Dragage Atlantique, who were able to put quay into service on time.

All of the activities were carried out using company equipment, which included a 2500 UHP unit, air bags, a decompression chamber and a Nitrox unit.

Categories: Civil Underwater Construction, Inshore, Offshore, Projects