For the Drôme Conseil Général (General Council of the Drôme Département), the overall project consists of developing the RD 518 road between the Royans and Vercors areas, between the municipalities of Saint-Eulalie-en-Royans and Barraques-en-Vercors, to increase overhead clearance from 3.50 m to 4 10m.

 

The Grands Goulets tunnel is 1,650m long. It is a two-lane road tunnel (one lane each way) that doubles the RD 518 at the so-called Grands Goulets section between the towns of Echevis and Barraques-en-Vercors.

 

The Civil Engineering works section mainly involves the following works:

 

- Civil engineering from the downstream head, excavation and stitching of the rocky facing included.

- Two-lane road tunnel approximately 1,650 metres long with a cross-sectional area of 70 m2 for approximately 1,595 m, and a widened cross-sectional area of about 110 m2 for 55 m

- 6 safety tunnels with a 10 m2 cross-sectional area over a total of 850 linear metres

- A set of safety recesses, turnaround areas

- Architectural work at the upstream head

- Architectural work at the downstream head with a fake tunnel

- Head and tunnel external works (road and utility works)

- Hydraulic structures at the downstream and upstream head

- The tunnel fire fighting system with tarpaulin water tank at the upstream head and the column installed along the entire length of the tunnel.