References

The underground bypass of the NICE-VINTIMILLE railway line represented more than 5 years works, separated into 5 packagess including the station (A01), a 3 km tunnel (A02), an open air section with retaining walls (A03), the crossing of the Sainte Devote valley (A04) and the connection to the existing tunnel (A05).

A01 package:

• East station: specific point for the excavation of a 288 m² section under a building, with low coverage of plain or heavily karstified Jurassic limestone.
• West station: 375 m with a 250 m² section implemented with two 5 m diameter pre-drillings.
• FEM calculations considering existing galleries and the building.

A02 package:

• Current tunnel: 1690 m tunnel excavated in five successive mayerss (cretaceous plain and altered marl-limestone, cenomanian marl, miocene sand, volcanic tuff) under a coverage reaching 180 m.
• Before the West station: gradual change from the station section to the tunnel section. Specific phasing with lancet arch, then widening.

Terrasol’s achievements:

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TERRASOL, together with SEEE and SDE engineering offices for the structures, performed the whole detailed design relating to geotechnical structures and soil-structure interaction:

• Finite element calculations for the various profiles,
• Tunnel face stability,
• Specific geotechnical consultancy relating to Miocene sands,
• Calculations for checking the excavation method (full section with face reinforcement),
• Decision-making and checking of the phasing with “vertically divided” section.