Gotthard: Longest Rail Tunnel cut-through with Leica Geosystems precision

(PresseBox) ( Heerbrugg, )
A new world record will be created on 15th October, when the miners working on the Gotthard Base Tunnel shake hands after the breakthrough between the Sedrun and Faido access points. For then the 57 km Gotthard Base Tunnel will be the longest rail tunnel in the world. The 15th October will also be a special day for Leica Geosystems - as the Heerbrugg-based company's surveying instruments are in use in all areas of the Gotthard Base Tunnel.

Specialists engaged on a wide range of activities in the construction of the Gotthard Base Tunnel place their trust in the reliability of Leica Geosystems surveying instruments and solutions. One of these specialists is Ivo Schätti, a senior engineer for the surveying consortium "Vermessungsingenieure Gotthard-Basistunnel" (VI-GBT). As the client's surveyors, the consortium is responsible for ensuring the correct position, level and direction during the driving of the megatunnel: "Put simply, our duty was to see that the hole was built in the right place," says Ivo Schätti. With the help of high-performance total stations, digital levels and optical plummets from Leica Geosystems, the position of the "hole" was continuously checked to ensure that it was within the accuracy required by the client AlpTransit Gotthard AG - 10 cm transversely and 5 cm vertically over the whole 57 km length of the tunnel!

Adrian Ryf, who is now head of geomatics with AlpTransit Gotthard AG, set a world record of his own at Gotthard: in summer 2005, using 28 Leica Geosystems GPS systems simultaneously, the former lecturer at the Swiss Federal Institute of Technology (ETH Zürich) and his students carried out what was then the largest-ever surveying campaign for an engineering project. The aim was to check the permanent station network. It had never been surveyed using GPS, which was a completely new technology in 1995. "With a construction time of almost 20 years in a tectonically active Alpine region, it was extremely important for the success of the project to check these permanent stations," explains Adrian Ryf. "We did not discover any shifts or differences - and thanks to the successful resurvey of the principal station network, the work at Gotthard could progress to completion on the basis of first-class survey data."

The contractors' surveyors, the specialists in the companies directly involved in driving the tunnel, also depended on the reliability and precision of Leica Geosystems instruments. As Reinhard Deicke, the surveying engineer responsible for the Bodio-Faido and Faido-Sedrun sections for Consorzio TAT (Tunnel Alp Transit-Ticino), explains: "I have worked with Leica Geosystems instruments for over 30 years and it has always been a good experience. Correctly performed maintenance and servicing are crucial to us. With Leica Geosystems as a partner, we were able to call upon excellent customer service." Over the whole of the construction period, TAT made use of several generations of high-performance total stations and levels, primarily for the control of the tunnel boring machine (TBM), setting out, profile measurement and levelling. "The instruments were subject to punishing conditions in the tunnel, having to operate 24 hours a day while retaining their precision in dirt and dust, and at extreme temperatures of up to 35 degrees or even higher. In spite of all that, not one of them failed - which speaks admirably for the quality of the instruments themselves, and for the good service provided by Leica Geosystems," says a satisfied Reinhard Deicke.

Leica Geosystems instruments are in use above ground as well, as the Gotthard Base Tunnel passes directly under three water reservoirs. "A tunnel always influences the water balance in the mountain. The loss in pressure due to the water extracted from the rock could result in the mountain literally collapsing," explains Ivo Schätti. To prevent this from occurring, we monitor the movements of the valley sides near the dam walls and in the areas leading up to them. High-precision total stations and Leica GeoMoS monitoring software were used to measure the movements. "The instruments have been in use since 2000 and always performed perfectly," says Ivo Schätti.

"The breakthrough in the Gotthard Base Tunnel, which is being built more or less directly on our doorstep, is yet another source of pleasure for Leica Geosystems. On the one hand, we are a Swiss company, and on the other hand our instruments have carried out most of the measurements and ensured that the required precision could be achieved. We are proud to play a part in this engineering project, the most prestigious of this century, and are delighted with its success, along with our customers and the rest of the project participants," states Jürgen Dold, CEO of Leica Geosystems.
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