In 1986, the 5,700-metre-long Kerenzerberg Tunnel was opened to traffic and must be upgraded in terms of safety technology in accordance with the guidelines and standards in force today. On behalf of the Federal Roads Office (FEDRO), the KER450 consortium is constructing the centrepiece of this overall renovation - the new construction of a safety tunnel (SiSto) arranged parallel to the existing tunnel, which will simultaneously serve as an escape route and as an exhaust duct.
The SiSto will be excavated over a length of 5,250m with a hard rock double shield TBM (ø 7.10m) and lined with steel fibre segments. As later escape routes, cross-connections (18 pieces) will be excavated every 300m and exhaust tunnels (52 pieces) to the existing road tunnel will be excavated every 100m by blasting to extract the exhaust air.
