This consultation concerns the construction of a new civil engineering structure by doubling the existing Larivot bridge on the RN1 in Guyana and its access embankments on the right bank (Matoury) and on the left bank (Macouria). It crosses a breach 1,200 m wide formed by the estuary of the Cayenne River.
The works to be carried out are mainly the following:
Concerning the main structure, prestressed concrete box bridge approximately 1,320 m long and 13 m useful width:
- construction of 19 piers built in a river, each founded on 4 concrete piles with a diameter of 1600 mm connected by a submerged footing;
- construction of two abutments on the banks in the mangrove area, founded on concrete piles with a diameter of 1,400 mm;
- construction of the bridge deck: precast prestressed concrete mono-caisson with a running span of 70 m; equipment.
Two basic solutions are retained for the structure:
- solution A: prestressed concrete box of constant height;
- solution B: prestressed concrete box of variable height.
Concerning the earthworks of access embankments: construction on compressible soil, vertical drains, soil improvement by rigid inclusions, lightened embankments, pre-loading embankments.
Main characteristics:
- useful width of the structure: 13 m;
- circular plan with a radius of 9,000 m;
- circular longitudinal profile with a radius of 18,500 m;
Solution A: mono-box precast prestressed concrete deck of constant height constructed as progress is made;
- length: 1318 m between the axes of the end supports;
- spans (20): 36 m + 63 m + 16 × 70 m + 63 m + 36 m;
- piers: circular hollow reinforced concrete shaft surmounted by an elliptical header.
Solution B: prefabricated prestressed concrete mono-caisson deck of variable height built by successive cantilevers;
- length: 1,306 m between the axes of the end supports;
- spans (20): 36.50 m + 56.50 m + 16 × 70 m + 56.50 m + 36.50 m;
- piers: circular hollow reinforced concrete shaft surmounted by a truncated cone-shaped header.
The works fall under category 1 within the meaning of the labor code (law nº 93-1418 of 12.31.1993). Provisional start of services: 1