Tunnel Beuren, L1210, Beuren Bypass

The existing L 1210 passes through the historically significant, densely built-up centre of Beuren and is fringed by many medieval gabled houses. As a result, it would not have been possible to expand the road running through the town without destroying its historic substance. After investigating various route alternatives and intensive deliberations it was decided to select the executed route alignment, which involved tunnelling below the existing as well as the future parts of the route. The country road L 1210 was relocated from within Beuren to a northern partial bypass within the community. The road runs through a tunnel, which is 397 m long with connecting groundwater basin passing beneath a built-up area. In the town itself the tunnel passes underneath the existing abutter road network. The first tunnel section's rectangular cross-section was produced from water-impermeable concrete. It was created in the form of a flat foundation (base slab). A 15 cm thick filter layer consisting of shingle concrete was laid beneath the tunnel floor, which was provided with a geotextile to separate it from the floor. This setup also served as a blinding layer. The central second section of the tunnel was produced by mining means using the NATM. It comprises a twin-shell vault construction with a shotcrete outer shell and a watertight in situ concrete inner one, which are separated by a plastic membrane. A napped foil was installed between the outer and inner shells per block, which was placed beneath the tunnel floor in order to cater for the groundwater flow. Grouting of the rock was undertaken at 2 points in order to prevent longitudinal drainage. Gentle blasting with advance crown, which was secured by lances in the roof, was essential on account of the composition of the strata, varying rock hardness and the proximity of buildings. A base invert was installed to comply with the requirements of a tight structure and in order to accept the prevailing water pressure. The vault was shielded against mechanical damage by filling it with protective and drainage matting, which at the same time catered for groundwater remediation. Here too, crossbars set at 20 m gaps prevented a longitudinal drainage effect.

Country: Germany
Region: Baden-Württemberg
Tunnel utilization: Traffic
Type of utilization: Road tunnel
Client: Land of Baden-Württemberg
Consulting Engineer: Ing.-Büro Winkler und Partner GmbH, Stuttgart
Contractor: Bilfinger Berger AG, Max Früh GmbH & Co. KG
Main construction method: Trenchless / open cut
Type of excavation: Drill-and-blast / wall-sole
Lining: Concrete formwork
No. of tubes: 1
Tunnel total length: 397 m
Cross-section: 100 m²
Contract Volume: € 11.7 million in total
Construction start/end: January 2003 to September 2004
Opening: 2004