Gotthard Base Tunnel: Surveying by the Client
Untertiteltext Englisch
On June 16, 2009, the tunnel boring machine Gabi I passed through the final metres of rock between the Erstfeld and Amsteg part-sections with a technical deviation of only some 14 mm crosswise to the tunnel and 5 mm with regard to the elevation. Following the equally successful results between Bodio and Faido as well as between Amsteg and Sedrun a further good result is anticipated from the main breakthrough between Sedrun and Faido in autumn 2010. The surveying experts can hardly await the moment of the breakthrough for this will finally reveal the fruits of their many years of labour.
At the very most 25 cm crosswise and along the tunnel and 12.5 cm in elevation are tolerated as deviations for the Gotthard breakthroughs. In order to remain inside these parameters with a high degree of reliability the surveying experts must press for accuracies, which are smaller by the factor of 2.5 in other words 10 cm crosswise and along the tunnel and 5 cm in elevation.
The objective of a minimal breakthrough error can only be attained providing that from the very onset all possible systematic and random influences on the surveying work are taken into...
