References
Underground car park Place d Arvieux
FRANCE, 2006 2008
Construction as a main contractor of a cylindrical underground car park comprising 7 basement levels.
Soletanche Bachy was contracted by the Etablissement Public d’Aménagement d’Euroméditer-ranée to construct as a main contractor an underground car park under Marseille's Place d'Arvieux. The car park is located between two office blocks and a metro tunnel.
The structure
The structure is a cylinder of 40 m diameter comprising the following :
- a circular diaphragm wall, excavated to a depth of 28m, in a marl soil,
- a cylindrical, reinforced-concrete central core 22m high, housing the vertical connections,
- a continuous helical ramp running down 7 levels and carried on radial beams, with about 40 parking spaces for light vehicles on each level on either side of the two-way ramp,
- a cover slab supporting the new architectural features and a new road across the square.
The works
Work began with the construction of the circular diaphragm wall, excavated using a hydrofraise in the gravelly alluvia and the marl. The capping beam and a beam with a 30m span and 3.30 to 6.00m height and the ramp support, were formed and concreted. The massive second beam allowed the simultaneous construction of the reception building during the open-cut excavation. The central core is carried on a footing. Eight successive lifts were required for its construction, using shuttering panels. The bottom level of the car park comprises a drainage slab with a permanent pumping system. From the next level up to the exit into boulevard de Dunkerque, the slab consists of a continuous helical ramp, constructed independently for each tier and carried on radial beams with no intermediate support. The structure was covered using precast and prestressed radial beams. The horizontal formwork was completed by prestressed pre-slabs carried on the beams. The slab was sealed following reinforcement and concreting. The technical and secondary work was carried out after completion of the associated works (ventilation shafts, lift, operations room).
Techniques
Regardless of site size, and providing it involves a significant proportion of works in the ground, Soletanche Bachy will handle the complete project, and all aspects of the works, including site supervision, excavations, foundations, civil engineering and all construction operations.
A diaphragm wall is a reinforced concrete wall that is made in situ. The trench is prevented from collapsing during excavation, reinforcing and casting by the use of supporting bentonite slurry. The slurry forms a thick deposit (the cake) on the walls of the trench which balances the inward hydraulic forces and prevents water flow into the trench. A slurry made of polymers can also be used.
Ouvrages
Soletanche Bachy undertakes the whole of a project from feasibility studies, through design to the complete construction on a turnkey basis.
Major urban excavations are one of the specialist activities of Soletanche Bachy. Such excavations are required for basements to buildings that are usually part of the foundations of the structure and also used for under-street car parks, cut and cover tunnels for roads, rail, metro and storm water tank...
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