The RD1091 road diversion project at the well-known “Séchilienne Ruins” place consists in shifting the alignment of the road to the opposite hillside in order to protect it from a predicted 3 million m3 landslide (this scenario is assumed to be the most probable in the short and medium terms by the experts).
This deviation, about 1000 m long and costing a total of €30M, includes a large excavation in the Montfalcon micaschists: maximum height 40 m with an excavated volume of 200,000 m3 and an exposed surface of 15,000 m².
The height of the cutting and the poor quality of the soil mass (micaschists globally highly fractured, presence of bands of coal-bearing formations and high water circulation) require reinforcement by dense soil nailing: more than 45 km of nails combined with shotcrete facing on 4/5ths of the surface.
TERRASOL was involved in the main phases of the project as geotechnical assistant to the Project Manager (Conseil Général de l’Isère): design and tender documents in collaboration with SITE ETUDES, VISA approval of the detailed design, and geotechnical follow-up of the works started in spring 2013 and carried out by the GUINTOLI/Bianco/NGE/GTS consortium.
- Design and tender documents
- Control of detailed design
- Geotechnical follow-up of works