The gripper TBM, manufactured by CRCHI, broke through at Brunnen, on the shores of Lake Lucerne, on February 20. It was launched in September 2024 to excavate the 1.23km-long drive.
The machine has a 3.85m diameter, is 110m long and has a total installed power of about 1,700kW. It is equipped with a normal rock bolting rig, shotcrete system, arch erector, and probe drilling, providing full support functions for bolting, mesh, and shotcreting. Safety facilities such as refuge chamber are also equipped.
During construction, the TBM successfully passed through water-bearing strata and achieved a zero-settlement crossing beneath an operational railway tunnel,using pipe-roof support.
The Igenbohl drainage tunnel, which a consortium of Implenia and Frutiger Gruppe are building on behalf of the cantons of Schwyz and Uri, is part of the A4 Neue Axenstrasse. The tunnel will divert mountain water run-off directly into Lake Lucerne.
