In early February 2016 at the south portal near the community of Hägendorf (Canton of Solothurn, Switzerland), work began on the Belchen renovation tunnel with a Herrenknecht Single Shield TBM. The tunnel, which cuts through the Jura Mountains between Basel and Lucerne, is of great importance to the north-south road traffic via Gotthard, but also for domestic Swiss traffic. Currently an average of 55,000 vehicles per day pass through the two existing two-lane dual carriageway tubes of the A2 road tunnel over a length of almost 3.2 kilometers. As a result of increasing rock pressure, both tubes are urgently in need of repair to ensure operational safety.
The refurbishment tunnel was driven through the mountain parallel to the existing tunnel system at a distance of between 40 and 116 meters. The geological conditions along the tunnel alignment were changeable. Soft layers of rock alternated with up to 225 MPa hard layers, in places with karstified and/or water-bearing transition zones. In addition, long sections of squeezing opalinus clay and swelling gypsum keuper had to be passed through. The contractor was therefore relying on single shield technology from Herrenknecht, which lines the tunnel completely with prefabricated concrete segments. With a diameter of nearly 14 meters, the machine is the largest of its type.
After commissioning of the refurbishment tunnel in 2022 the two existing tubes dating from the 1970s will be renovated one after the other, so that as before, two lanes will be available in each direction, north and south, and traffic can flow without hindrance.
With the Herrenknecht Single Shield TBM, the Belchen Tunnel crew had the best equipment for the challenging ground conditions. They won an advance of three months compared to the original schedule. The jobsite celebrated the successfull breakthrough at the northern portal at Eptingen after approx. 16 months of tunnelling on June 21, 2017. Site manager Sergio Massignani summarized: "Thanks to the comprehensive knowledge of the ground conditions from the two existing tunnel tubes, coupled with our experience and Herrenknecht's know-how, the machine was optimally designed for the demanding requirements of the alignment of the Belchen rehabilitation tunnel."
Sanierungstunnel Belchen (German)