Service des Routes, Transports et Cours d'Eau (SRTCE) du Canton du Valais - Switzerland
October 2012 - December 2017
- GITEV PRA (Pilot),
- Nunatak (Architect) - Bruchez).
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.
- 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).