Evouettes tunnel

Evouettes tunnel

Client

Service des Routes, Transports et Cours d'Eau (SRTCE) du Canton du Valais - Switzerland

Execution

October 2012 - December 2017

Collaboration

  • GITEV PRA (Pilot),
  • SRP,
  • Nunatak (Architect) - Bruchez).

Total costs

72 mio EUR

Project description

The Evouettes bypass on the H144 is a two-way road which improves the link between Villeneuve and St-Gingolph. The topography led to the following works:

  • two road junctions (total L = 473 m);
  • two tunnel entrance cuttings (total L = 163 m);
  • two rectangular cut-and-cover tunnels (total L = 49 m);
  • two cut-and-cover tunnels with a profile similar to that of the main tunnel (total L = 59 m);
  • a tunnel (L = 657 m, internal radius = 5.30 m);
  • an emergency tunnel (L = 120 m).

BG is in charge of the design and sizing of the tunnel, the emergency tunnel and the cut-and-cover sections which have the same profile as the tunnel.

Details relating to the tunnel:

The key technical constraints are:

  • Underground construction below the residential zone of Evouettes d'Amont. Monitoring of settlements required.
  • Underground construction below the Tové torrent. Temporary waterproofing of the stream bed required.

The excavation extends through loose ground (sandy-gravelly and silty-gravelly moraines). The geological conditions are described as difficult. Systematic ground reinforcement is required.

The excavation of the Evouettes tunnel ascends for around 150 m before descending for around 500 m from the north portal to the south. The full cross section is excavated using a mechanical excavator.

The ground support enabling works include:

  • 45 near-horizontal overlapping jet-grouted columns (min. diameter 80 cm; length 12 m) distributed around the excavation perimeter of the tunnel and at the piers. The columns have been installed at an angle of 7.29° to the axis of the tunnel to enable successive sets of columns to overlap each other by 3 m.
  • 13 jet-grouted columns (min. diameter 80 cm, length 12 m) at the leading edge of the excavation. These columns are inclined at between 0 and 5° to the horizontal.

The ground support consists of sprayed fibre reinforced concrete followed by a sprayed concrete layer reinforced with steel girders and a welded mesh.

The temporary invert is formed using poured concrete reinforced with HEB 180 or 220 beams.

The permanent invert and lining are of unreinforced concrete.

Services provided

  • Feasibility studies;
  • Scheme design;
  • Compilation of tender documents, analysis of tender returns and adjudication proposal;
  • Construction design;
  • Direction of the works;
  • Commissioning and handover;
  • Role as Client's Representative (BAMO).

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