The Belchen Tunnel, which cuts through the Jura Mountains between Basel and Lucerne, is of great importance to the north-south road traffic via Gotthard as well as for domestic Swiss traffic. Currently an average of 55,000 vehicles per day over a length of almost 3.2 kilometers pass through the twin tube road tunnel of the A2 road tunnel with two lanes in each direction. As a result of increasing rock pressure, both tubes are urgently in need of repair to ensure operational safety.
The rehabilitation tunnel now completed was excavated through the mountain to the west of the two existing tubes at a distance of 40 to 116 meters from the existing tunnel system. Along the tunnel alignment the miners from Marti Tunnelbau AG mastered the challenging geological conditions with the Herrenknecht Single Shield TBM with overburdens of up to 360 meters. Soft layers of rock alternated with up to 225 MPa hard layers, in places with karstified and water-bearing transition zones. In addition, long sections of squeezing opalinus clay and swelling gypsum keuper had to be passed through. Site manager Sergio Massignani summarized after the breakthrough: "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."
Machine- / Project data S-947 Belchen Rehabilitation Tunnel
- Machine type: Single Shield TBM
- Shield diameter: 13,910 mm
- Drive power: 3,500 kW
- Tunnel length: 3,200 m
- Geology: Gypsum, clay, lime, dolomites, marl
- Customer: Marti Tunnelbau AG
- Client: Swiss Federal Roads Office FEDRO