Underground bypass of the Monaco railway line: outside structures

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:

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
PERIOD :  1993-1998
Owner : Territory of Monaco
Project Manager : SNCF
Main Contractor and Client : Group of contractors led by SOBEAM
Main specifications :  

  • Underground station, 3 km tunnel, crossing of the Ste Dévote valley and connection to the existing tunnel
  • Earthworks volume: 450,000 m3
  • Time limit: 5 years
  • Amount of the works: 228 M€ (excluding VAT) 
  • Amount of Terrasol services: 183 k€