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).

A03 package:

• Checking of the umbrella arch in the portal zone.
• Stability calculations, for zones with temporary or permanent Monaco walls, including seismic properties.
• West tunnel portal: built in screes, with 30 m umbrella arch, divided section excavation, and with jet-grouting under the base of steel arches and for the raft.
• Retaining wall (95 m long, 14 m high) then cut-and-cover (30 m long, 20 m maximum height) excavated in a steep natural slope made of screes. This vertical wall is built using the “Monaco” method: permanent panels made of in reinforced concrete with active anchors.

A04 package:

• Structure partially outside, located in the Sainte Dévote valley, with excavations over 35m height in Jurassic limestone and implementation of anchors.
• Stability calculations using TALREN software developed by TERRASOL and considering plane failure surfaces (along fractures).

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
• Checking of umbrella arches
• Stability calculations for the retaining walls
• Tunnel face stability
• Geotechnical consultancy