ABSTRACT
The new Bözberg Tunnel is a double-track railway tunnel. He is roughly 2.7 km long and thus the longest of the tunnels, which are being excavated or enlarged for the realization of the so-called “4-metre corridor” on the Gotthard artery through Switzerland. The excavation methods have been chosen according to the expected geology: conventional excavation in soil and by means of a single shielded TBM in (swelling) rock. After a short general overview of the project, the paper focuses on the tunnel section which runs in rock. Particular emphasis is put on the TBM break-through, which – in spite of the very low overburden of 1–2 m of sound rock – occurred successfully in November 2017 close to the existing railway line without interference of the railway operation. For this purpose, the implementation of auxiliary measures (e.g. triple pipe umbrella), a continuous monitoring and exhaustive risk management were necessary.
