ABSTRACT
The excavation of the 57.5-km-long twin-tube tunnel of the Lyon-Turin railway line is now 22% complete. On the Italian side, the excavation of the interchange niches in the Maddalena exploratory tunnel - preparatory to the launch of the future CO3-4 construction site that will excavate the Italian section of the base tunnel - was completed in December 2023.
In this paper, we compare the geological and geomechanical evidence derived from the excavation of the niches using the traditional method with the data previously acquired with the TBM Gripper excavation of the pilot tunnel completed in 2017.
The results obtained using a different excavation method made it possible to improve the geological model for an overburden sector in which rocks belonging to different tectonometamorphic units of the Ambin Massif are crossed. In this section, the Maddalena safety site will be constructed as part of the future CO3-4 construction site work.
