Design

The launching facility acts as a lift between sea level and the dock water level. It enables the vessel to be moved vertically and horizontally and acts like a slipway but incorporating a reverse hydraulic process.

 

THE STRUCTURE COMPRISES:

• one transfer platform (70m x 170m), set above sea level;
• a harbour basin (65m x 135m) that opens out to the sea;
• two abutments and a sill between, which support the 65m sea gate;
• one quay platform measuring 27m x 89m, which houses the pumping plant;
• two gates: a seaward caisson type gate and a landward modular gate;
• two mooring dolphins.

 

The conforming design envisaged sheet pile wall held by ground anchors to form the basin. Soletanche Bachy came up with an alternative solution that replaces the sheet piles with diaphragm walls. The diaphragm wall was mostly cantilever and was constructed with T panels. The wall along the transfer platform was constructed using flat panels.

 

Construction

300,000m³ of sand was first brought in to make a working platform for the land construction of the diaphragm walls and pile installation. Diaphragm walls were constructed all around the basin and also along the perimeter of the two abutments. A sheet pile cofferdam, connected to cast-in clutches in the diaphragm wall, was constructed between the abutments, to allow the construction of the sill and the abutments in the dry. The sill was founded on barrettes and concrete piles.

 

Dewatering of the sill and abutments was achieved with 10 deep wells. All works were done in the dry. Cast-in couplers were used to connect the diaphragm wall to the abutment structure. Leaving a bund at the sea end allowed the basin excavation in the dry. Dredging to final depth was then carried out inside of the basin. The transfert platform is founded on CFA piles.