Dredging and Backfill2019-03-17T11:27:47+00:00


Dredging and Backfill

The structure that will constitute 6 hectares of new land is constructed and protected by a perimeter belt of 18 caissons weighing 10,000 tons each and reaching 27 meters in height.

Photo: Bouygues TP MC

The dredging phase began in April 2017 with the removal of the existing rip-rap and the dredging of 600,000 m3 of polluted silt unfit for this type of construction. The objective is to expose the rocky part of the seabed that will be the base for the work site. After the dredging is complete, backfilling operations begin.

Three ships complete the dredging. First, the rip-rap and polluted sediment is removed and properly disposed of using the Mimar Sinan, a backhoe dredger, and the Tiger, a split hopper barge. Next, the unpolluted sediment is removed via a giant computer controlled vacuum aboard the Francis Beaufort, a trailing suction hopper dredger, which stores the sediment in its 11,000 m3 tank before carefully submerging it offshore in 200 meter deep Monegasque territorial waters.

Video: Bouygues TP MC

The Simon Stevin, a fall pipe rock installation vessel, completes the backfilling using a robotic conduit to place 1.5 million tons of rock. The rock has been very carefully manufactured from the Chateauneuf-les-Martigues quarry in southern France. The rocks are measured to specific sizes and cleaned multiple times to decrease any risk of turbidity during installation.

Video: Bouygues TP MC

When the backfilling is completed, the area is vibro compacted and levelled to create the solid foundation on which the caisson belt will be installed.

Video: Bouygues TP MC