- Project Owner : AUTOROUTES DU SUD DE LA FRANCE
- Project management : INGEROP CONSEIL ET INGENIERIE
- Mission : geotechnical project management
- Cost of the mission : AVP/PRO : 552 k€ ; VISA/DET : 434 k€
- Mission date : 2006-2016
BRIEF DESCRIPTION AND CHARACTERISTICS OF THE PROJECT
The study carried out by GEOS Ingénieurs Conseils is part of the project to relocate the A9 motorway in Montpellier.
Half of the 23 km route involves widening the existing motorway and the other half a new route.
In terms of earth movements, the route involves a deficit: 3.1 million m3 of backfill and 1.2 million m3 of excavation.
In the central part of the new route, the project crosses a vast plain of alluvial deposits (Lez-Lironde, Lantissargues, etc.) and comes into contact with the CNM TGV line currently under construction in a sector where compressible soils with a high degree of lateral variability have been identified.
The embankments, which are 6 to 12 metres high, were placed in advance to minimise their interaction with the CNM project. Vertical drains were installed under the most sensitive technical blocks.
MISSION
In collaboration with the engineering teams of INGEROP, the project manager, GEOS carried out the geotechnical design studies (Motorway Preliminary Design) and is monitoring the works (VISA, DET).
According to standard NFP 94-500, this involves the sequence of tasks G1-PGC/G2-AVP/G2-PRO/G2-DCE/ACT and G4. These studies covered the following points in particular:
- Definition of the geological, geotechnical and hydrogeological context of the project,
- Drafting of the geotechnical sections of the TCFH APA,
- AVP and PRO: Studies of earthworks (stability, slopes, settlement) and OA,
- Definition of comfort measures (masks in excavations, vertical drainage and preloading of technical blocks),
- Definition of the monitoring to be carried out,
- ACT: Technical assistance in drawing up the tender documents and analysing the bids,
- VISA of the geotechnical execution studies, approval sheets and execution procedures,
- DET: Geotechnical supervision of works.
