Vaihingen Eastern Bypass, Österfeld Tunnel

The Vaihingen eastern bypass with a total length of 1.9 km links up with the B 14 (Vaihinger cloverleaf) and runs parallel to the railway tracks at the Unterer Grund parking facility. It passes through the Österfeld Tunnel undercutting the Paradiesstrasse and the tracks of the Gäu railway and S-Bahn over a distance of 400 m by mining means. The Nesenbachtal valley is spanned by means of a 170 m long bridge The road continues along the southern valley side beneath the Höhenrandstrasse in the 780 m long Hengstäcker Tunnel, which was built via cut-and-cover. The roughly 400 m long Österfeld Tunnel joins up with the causeway at Unterer Grund. The tunnel initially runs parallel to the Gäu railway and S-Bahn tracks until the Don Carlos Bridge is reached. Over the first 100 m of this area, there is a supporting wall at the foot of the neighbouring railway cutting. ln addition, there are a number of residential areas within the tunnel's zone of influence, with one house having to be directly undercut. Behind the Don Carlos bridge, the tunnel crosses the cutting for the 4-track railway line at a sharp angle and ends up in the northern flank of the Nesenbachtal shortly afterwards. The tunnel is located some 6 to 14 m beneath the surface, with the slightest overburden directly beneath the railway tracks. A jaw profile with a maximum clear width of 10.40 m and a maximum clear height for the inner shell of 8.90 m was selected. The watertight concrete inner shell is 40 cm thick on average. A tunnel excavator was used to extract the altogether 98 m² large cross-section. In the process, the cross-section was divided into an advance crown heading and a follow-up bench and base excavation. For static reasons and with regard to minimising the surface settlements, the crown was provided with a temporary shotcrete base. The distance between the bench/base and the crown amounted to at least 50 m. For the crown drive, the lengths of advance varied between 80 cm and 1.20 m, for the bench and base between 1.60 and 3.00 m. Rapid ring closure was attained for the shotcrete shell both for the crown as well as for the bench/base excavations. This turned out to be a well worthwhile measure for minimising settlements especially when undercutting houses and the railways.

• Country: Germany
• Region: Baden-Württemberg
• Tunnel utilization: Traffic
• Type of utilization: Road tunnel
• Client: Landeshauptstadt Stuttgart
• Consulting Engineer: WBI, Prof. Dr.-lng. W. Wittke
• Contractor: Ed. Züblin AG, Bilfinger + Berger Bau AG
• Main construction method: Trenchless
• Type of excavation: Excavator
• Lining: In-situ concrete
• No. of tubes: 1
• Tunnel total length: 400 m
• Cross-section: W/H = 11 m/10 m