ABSTRACT
This paper compares different design and construction approaches for TBM tunnels in difficult rock conditions, based on the experience gained in two major railway base tunnels currently in construction: the Brenner Base Tunnel (Italy-Austria) and the Moncenisio Base Tunnel (Italy-France). The case study of Brenner Base Tunnel focuses on the Hard-Rock Gripper TBM excavating the exploratory tunnel on the Austrian side and the 3 Double Shield TBMs excavating the exploratory tunnel and the main tunnels on the Italian side. The new Lyon-Turin railway project involves the construction of the 57.5 km twin-tube Moncenisio Base tunnel, with approximately 75% of TBM tunnels. The paper presents the experience gained during the construction of the first section excavated by a Single Shield TBM. Other major challenges will be highlighted, such as the design solutions for Shielded TBMs excavating potentially swelling rock and the Dual Mode TBMs planned for the Italian main contract.
