ABSTRACT
The connection between the Lyon-Turin high-speed railway line and the historical railway is called Interconnection Tunnel, which foresees two tunnels, almost two-kilometer-long with excavation sections from 80 m2 up to 361m2. The interconnection tunnels underpass two existing tunnel infrastructure: the historical railway Tanze tunnel with an overburden of 70 m; two tubes of highway A32 Prapontin tunnels with an overburden of 25 m. The tunnels will be excavated using the D&B method with low vibration level allowed. The overburden between the Interconnection tunnels and highway A32 Prapontin Tunnels is around 25 m. Regarding geological and geotechnical information, the rock mass has a good/optimal quality with a compression uni-axial strength approximately about 70 MPa and GSI avg = 50. A 3D model for a back analysis process during the excavation phases will be necessary. To exclude any influence between the excavation of the interconnection tunnels and other existing underground structures, it is essential to monitor the deformation evolution, the rock mass-support system interaction, the stress analysis in the support structures and the plastic zone.
