The Tartaiguille tunnel, 2400 m long, is one of the most important underground structures of the new Méditerranée high speed railway line. Involved with the group of contractors QUILLERY/DEMATHIEU ET BARD since the call for tender, TERRASOL carried out the detailed design and geotechnical consultancy throughout the project.
From the beginning of the works, major convergence was observed during excavation in half-sections in the marl of the South portal. After an important series of soil testing and in situ measurements (borehole slotter, dilatometers, etc.), combined with finite element calculations, it was shown that deformations were related to high horizontal stresses (K0 about 1.2). The finite element calculations highlighted that, considering these high stresses, the traditional excavation method was not applicable in the clays of the central section. It was finally decided to switch to a full cross-section excavation method, allowing to complete the works within the time limit.
The technique chosen for the excavation of the tunnel central section in the Stampian clay, developed together with Professor Lunardi (full section excavation, tunnel face reinforcement with 150 fiberglass bolts 24 m long, raft cast immediately after excavation, implementation of the lining 20 to 30 m from tunnel face) proved its efficiency in difficult soil conditions: compliance with deadlines, displacements control, staff safety. This first real application of the method in France (world record in terms of excavation section) will probably be followed with others.
- Tartaiguille: le tunnel de toutes les audaces (Le Moniteur N°4960 dated 18/12/1990).
- Mise au point sur le chantier de Tartaiguille (Le Moniteur N°4885 dated 11/07/1997)
- Méthode pleine section pour la traversée des argiles: magazine Travaux N°742
- Influence of the Ko coefficient on the design of tunnels in hard soils (World tunnel Congress’98 – Sao Paulo)
- La traversée des argiles du tunnel de Tartaiguille (Tunnels et ouvrages souterrains N°153 May/June 1999)
- Detailed design of the portal structures (soil-nailed slopes),
- Detailed design of underground structures (finite element calculations),
- Works follow-up,
- Participation in the steering committee for full-section excavation of the central part.