Geotechnical Investigations for Alpine Base Tunnels (Turin–Lyon Line)
Ref. No.: 2025DOS0768413
Deadline: 17 February 2026
Procedure: Negotiated with prior call for competition

A negotiated procedure with prior call for competition has been launched for deep drilling investigations (over 400 m) to obtain geological, hydrogeological and geotechnical data for summary reports related to three major Alpine tunnels:

• Chartreuse Tunnel: 24.7 km
• Belledonne Tunnel: 19.7 km
• Glandon Tunnel: 9.5 km

These tunnels form part of the access routes between Avressieux and Saint-Jean-de-Maurienne to the new Turin–Lyon Alpine line.

Key Geotechnical Aspects and Investigations

• Geological Complexity: The tunnel traverses highly variable geology, ranging from hard rock (Ambin gneiss) to unstable, fractured, and water-bearing material, such as the Houiller Productif formation.
• Deep Monitoring: With overburden depths ranging from 1,000 to 2,200 meters, specialized, continuous monitoring was required to manage intense geological pressures and avoid failures, particularly in zones experiencing spalling or squeezing.
• Site Investigation Methods: The investigation phase included extensive core sampling, seismic surveys, and preliminary exploratory galleries (e.g., Saint-Martin-La-Porte) to verify geological assumptions.
• Excavation Challenges & Solutions:
• Saint-Martin-La-Porte: A TBM was used to cross a 9 km section, including a 1.3 km stretch of highly challenging ground, to validate excavation methods.
• Controlled Deformation: In high-stress zones, a controlled deformation support system was utilized to stabilize walls.
• Mixed Ground: Specific, varied excavation methods (TBM or conventional) were deployed tailored to the local rock mass characteristics.
• Geotechnical Classification: The excavated materials are classified according to A.F.T.E.S. G.T. 35 recommendations for potential reuse.
• Environmental Management: Geotechnical work included monitoring water management in areas like the Cenischia Valley, where mixed-shield TBMs with sludge treatment were utilized. 

The project, overseen by TELT (Tunnel Euralpin Lyon Turin), utilizes these investigations to manage safety and optimize the, with, as of 2024, significant milestones achieved in both French and Italian sections. 

Estimated dispatch of invitations to tender:
25 February 2026

Contract value:
EUR 13.22 million (excluding VAT)

Contract duration:
13 July 2026 – 13 July 2029

Client:
SNCF Réseau, Saint-Denis

Contact:
Tel: +33 6 09 76 73 69
Email: eddy.combier@reseau.sncf.fr

Tender documents & submission:
https://sncf.bravosolution.com/web/login.html

EU notice:
https://ted.europa.eu/en/notice/-/detail/27372-2026 05/26.