After having completed the contract for an Aker Wirth tunnel boring machine of 8 m diameter in December 2009, and following an optimal workshop acceptance, the various individual parts of our latest tunnel boring machine left the plant in Erkelenz at the beginning of July. The components are now on their way to Switzerland where a tunnel is to be bored for the extension of a hydroelectric power plant.

In the last few weeks before the delivery the machine was put through its paces during the course of a comprehensive test programme at our plant: the basic functions were checked and the main drive, with its more than 4000 hp, was submitted to a 24-hour endurance test – an obligatory test for every Aker Wirth tunnel boring machine. Our end-to-end, professional quality assurance system is highly appreciated and valued by construction companies and project owners.

Background information

By the beginning of August all the components will have been transported to the construction site in Tierfehd in the Swiss Canton Glarus, directly on the way up to the Klausenpass (approx. 80 km south of Zürich). On site the machine will be assembled and ready to start drilling operations in the middle of October 2010 as scheduled. The machine is to bore a 4 km access tunnel to the underground cavern which houses the machines for the new pumped storage power plant in Limmern.

The tunnel has a diameter of 8.03 m and goes up from 800 m (above sea level) to about 1700 m at a constant gradient of 24%. For this inclined tunnelling the Aker Wirth TBM has been equipped with additional securing fixtures to cope with rising gradients. Up till now rising inclinded tunnelling has only been carried out by machines up to a diameter of 6 m. The tunnelling of the Limmern access tunnel will therefore be the largest inclined operation of this kind to have ever been carried out with a tunnel boring machine.

The extension of the existing production facility of the Kraftwerke Linth-Limmmern AG with the new pumped storage plant is an important project for Switzerland’s future electricity supply. The order for the tunnel boring machine was placed with Aker Wirth by “ARGE Zugangsstollen  Limmern” (AZL) who will carry out the construction of the tunnel. This consortium consists of the companies Rothpletz, Lienhard + Cie AG, Aarau (Switzerland), Baresel GmbH, Stuttgart (Germany), Wayss & Freytag, Frankfurt (Germany), G. Lazzarini & Co.AG,  Chur (Switzerland), Andrea Pitsch AG, Thusis (Switzerland) and Ragotti+Weber Bau AG, Nestal (Switzerland).

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