The Katzenbergtunnel
In October 2003, Wayss & Freytag Ingenieurbau AG started on the construction of Katzenberg Tunnel for German Railway in a joint venture. The 9,385 m long tunnel consists of two tubes (Æ outer diameter 10.80 m; Æ inner diameter 9.60 m) and is part of the long-distance railway line between Freiburg and Basel in the Markgräfler Hügelland (hilly country), approx. 30 km North of the Swiss border. The north portal is located on the municipal territory of Bad Bellingen, the south portal on the territory of Efringen-Kirchen.
The two single-track tubes, each 8,984 m long, are currently being driven with two mix-shields, whereas the tunnel drive in the rock section is carried out without support of the tunnel face and in soft ground with liquid support. The first TBM started in June 2005, the second TBM four months later. The TBMs drive through tertiary sedimentary rocks and, in a section of 800 m, also through Jurassic limestone. The extreme water encroachment which was five decimal powers higher than predicted caused a special difficulty. During water level observations a total of up to four different groundwater levels could be found. The maximum water pressure is 9 bar.
The total of 19 cross-passages each 500 m apart are carried out using the mining technique, whereas it is planned to support the structures in advance by bars and anchors with shotcrete lining. The tunnel lining of the tubes is carried out with 60 cm thick reinforced concrete segments, whereas the gap between concrete segments and ground will be grouted with mortar. For both tunnel tubes a total of approx. 63,000 segments are to be placed.
Further details:
- 1.8 m m³ excavated material
- 95 m² /m cross-section / tube
- 110 m maximum cover
- 25 m minimum cover
- 20 m² /m excavation cross cut
- 2.0 m ring width
- 6 pcs. concrete segments plus 1 keystone per ring