Amsteg-Sedrun Section of Gotthard Base Tunnel Completed Nine Months EarlyThe 17 km west section of the Gotthard base tunnel between Amsteg and Sedrun holed through on 17th October, 2007, with an impressive nine months ahead of schedule. Tunnellers from Sedrun worked with high precision, joining the two stretches with a vertical deviation of only one centimetre and a horizontal deviation of just under 15 cm. View pictures here. The early breakthrough after a final blast is particularly noticeable since the tunnel crosses squeezing problematic rock conditions of the Tavetsch intermediate massif. A difficult zone with a length of approximately 1,200 metres and 800 metres under Sedrun had to be crossed while the tunnel tended to close once excavated under the immense rock pressure. To provide support for keeping the excavated cross-section open, deformable steel rings were installed which gradually close under the pressure of the squeezing rock until their maximum supporting force is attained. Although this technology was already known from German coal mines, it had never before been applied at large scale in tunnel construction. The concept of deformable steel rings that was developed especially for the squeezing rock conditions of the Tavetsch intermediate massif proved a complete success. Click here. The TBM that started from Amsteg at the end of May 2003 reached the limit with the Sedrun lot one year ago in the west tunnel, after digging nearly 11 kilometres. The 6 km of the Sedrun section has been drilled and blasted since summer 2004. The other TBM in the east tunnel completed its job in June 2006 on the Amsteg section. The east tunnel is expected to break through in summer 2008. Both tunnel boring machines reached their destination several months ahead of schedule: nine months in the east tunnel and six months in the west tunnel after each driving a length of 10.7 km. Click here.The total cost of the Gotthard base tunnel is expected to balloon to CHF11.74 billion, which is one billion more than envisaged. Even if nearly 70% of the base tunnel has now been bored, problems may still arise. Therefore, approximately CHF2.75 billion has been budgeted to face possible additional risks, so that the final bill for the Gotthard base tunnel totals nearly CHF14.5 billion. The final cost of the new railway lines through the Alps, including the Loetschberg tunnel in its full traffic configuration scheduled for 9th December, should amount to CHF19.1 billion.As of 1st October, 2007, out of the total length of 153.5 km of the tunnel system being constructed under the Gotthard, 105.1 km or 68.6% had been excavated. A total of 480 metres has been driven in September 2007. Click ch/22. Visit www.alptransit.ch 44/07.