Zourite, a Kraken for Maritime Works

The joint venture NRL (Nouvelle Route du Littoral), led by VINCI Construction Grands Projets, has been awarded for the construction of a 5 400 m-long viaduct over the sea on North-West of La Réunion island.

Because of the weather constraints of the Indian Ocean, the project team made the choice to optimize precast segment (inland) and to minimize maritime works (offshore). In maritime works, Sheerleg are commonly used for heavy lifting, but unfortunately those barges do not withstand the weather condition. Indeed, the maximum wave height it can face is around 0,5m during lifting or transportation. And the wave conditions in La Reunion do not provide enough weather windows (<0,5m) to install 150 precast elements over the sea. Thus the team had to imagine a new barge capable to withstand higher weather conditions and install the precast elements with the accuracy required by the viaduct.

That was in that context that Zourite came up. It is an Heavy lift jack-up barge able to load on, transport and load off precast segments (maximum weight 4 600 t). It is fitted with 8 jacking system 4 000 t capacity which allows the barge to stand on her legs over the waves of La Reunion, to achieve the segment installation or the civil works offshore. It can even jack-up over the cyclonic wave if necessary.

Each segment is skidded from the precast yard onto the barge and sea-fastened for sailing. Then, arriving on site, a dynamic positioning system gives the ability to place the barge accurately on site. While maintaining the position, the legs are lowered until the barge begins to jack-up. When the safe level to lift is reached, the 4 800 t capacity gantry crane is used to lift the item, skid it along the deck, and lower it into the sea.