56 METERS IN JUST 24 HOURS.
After a major overhaul, the two Herrenknecht Gripper TBMs, Gabi 1 and 2, completed the northern Erstfeld-Amsteg section with a length of just over 7 kilometers in 2009. The geological conditions there were almost ideal. This meant a Gotthard tunnelling record could be set in late summer 2009. In the space of only 24 hours, Gabi 2 chomped its way through no less than 56 meters of mountain – a world record for a tunnel boring machine of such dimensions. On June 16 and September 16, 2009, the construction site teams in the north reached their destinations in Amsteg after only 18 months, that is, six months ahead of schedule. This breakthrough was a prime example of the tunnel builders’ and the machines’ precision. Both TBMs had deviated from the ideal line, horizontally by 4 millimeters and vertically by 8 millimeters – millimeter precision in the truest sense.
The Worms.
At this time, Sissi and Heidi were still working in the mountain in the south. Although Heidi had some problems with a rock collapse in the western tube between Faido and Sedrun in March 2010, the subsequent stabilization measures only interrupted tunnelling until July 2010. Luckily enough, this event had almost no impact whatsoever on the project schedule. Work continues, including that of the two (vault) lining units supplied by the Herrenknecht branch company Maschinen- und Stahlbau Dresden, which follow the two tunnelling ‘ladies’ at a respectful distance. These 600-meter-long ‘worms’ lay drainage pipes, install sealing systems and concrete the vaults in twelve-meter stages. In a nutshell, they prepare the tunnel tubes, with top monthly performances of 600 meters, for the installation of the railway technology.
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