ABSTRACT
The Turin-Lyon High-Speed rail project involves constructing complex underground infrastructure. The CO7 site includes the Base Tunnel between Saint Martin La Porte and La Praz and a firefighting cavern at the Saint Martin La Porte access. The design focuses on the intersection of the technical cavern (22m diameter, approximately 380 m² excavation) and the base tunnel (12.5m diameter, approximately 125 m² excavation) in black schists and sandstone at a 680m overburden. Traditional rigid linings risked excessive stress and high costs. Instead, a deformable primary lining with Compacfoam, a High-Strength Expanded Polystyrene (HS-EPS), was adopted. This lightweight yielding support reduces stiffness, stress, and costs. Complex numerical models using FLAC 3D validated the deformable behavior of the solution, confirming its effectiveness.
