Cut and Cover

In order to proceed with the excavation and construction of the underground structures, it is

necessary to move all the utilities grids (water, electricity, gas, telephone) installed beneath the roadway. The

works alternately involve half of the via Nizza roadway. This phase lasts 12 months.

Once the underground services have been moved, construction begins with the insertion of interconnected micropiles to form the side walls of the tunnels and sustain the ground surrounding the excavation. The works are carried out in parallel with the moving of the underground utilities, in the same area and with the same time frame.

In support of the walls constructed with micropiles, the covering is constructed. This covering in concrete facilitates the restoration of the road surface and improves protection of the buildings from dust and noise.

The works involve the centre lane of the roadway.

This phase will last about 6 months.

While the area freed of the construction site on the surface can be used for parking, excavators dropped through an opening in the covering can proceed with the excavation of the underground tunnel. The construction site occupies the central lane of the roadway in this space. In order to guarantee the strength and stability of the walls, yet another concrete covering is constructed at about 6 metres underground for the tunnel and about 20 metres for the stations. This phase will last about 15 months.

Once the excavation has been concluded and the foundation laid, the finishing work begins (safety devices, lighting systems, tracks, escalators, etc.). This phase lasts about 10 months.