Steep TBM drive for Swiss hydro scheme
Steep TBM drive for Swiss hydro scheme Feb 2010
Aker Wirth news release
A new 8.03m diameter Aker Wirth TBM is set to drive the world's largest inclined TBM tunnel.
On order by Swiss contractor Ragotti+Weber Bau AG, the rock TBM will be used to drive a 4km long 24% inclined access tunnel from an access portal to a new subterranean machine hall of the Linth-Limmern power plant expansion project in Switzerland.
From the access gallery portal near the village of Linthal in the Canton of Glarus, south of Zurich, the TBM will drive the 8.03m diameter pressure tunnel on its constant 24% incline gradient from elevation 800m to approximately 1,800m above sea level.

Plan of the scheme with the inclined access tunnel in red

"Several inclined drives of up to 6m diameter have been completed to date and Aker Wirth TBMs have been used successfully on inclined tunnel projects since the mid-1960s," said Aker Wirth CEO Christoph Kleuters, "In fact one of our first hard rock TBMs when we entered the TBM market in 1967 was for an inclined tunnel. We believe this is the largest diameter inclined TBM tunnel so far at 8.03m diameter."
The TBM has been equipped with additional safety features for the steep inclined drive. For this special task, the manufacturer partnered with Rowa Tunnelling Logistics AG of Switzerland to build a backup system to manage muck haulage and assist safe and efficient tunnel support installation. Aker Wirth and Rowa have collaborated on several TBM orders over many years and "our customers can rely on the more than 40 years experience we have gathered in building these machines," said Kleuters.
The €20 million TBM system is ordered by Ragotti+Weber as subcontract for the tunnel drive to the project's main contractor ARGE Zugangsstollen Limmern, a consortium that consists of Rothpletz, Lienhard + Cie AG (Switzerland); Baresel GmbH (Germany); Wayss & Freytag (Germany); G. Lazzarini & Co. AG (Switzerland); and Andrea Pitsch AG (Switzerland).
As well as the access tunnel, the project comprises a new underground machine hall, two high pressure tunnels from the upper Lake Mutt to the machinery hall, and two tailrace tunnels of about 500m each into the lower Lake Limmern. A new gravity dam will be built for Lake Mutt and since the existing Tierfehd compensating basin is too small, an additional basin will be built to enable the pump storage machines to be used more flexibly.
Extension of the Linth-Limmern pump storage power plant for an investment of some SFr 1.8 billion has been long anticipated. The new facility will boast pump and turbine capacities by 1,000 MW, boosting the scheme's output from the current 450MW to 1,450MW. The massive increase in power output also requires new 220kV and 380kV connections to the Swiss supergrid.
Construction is expected to take a good five years, and it should go into operation in 2015/2016. Manufacture of the access tunnel TBM at the Erkelenz plant of Aker Wirth will be completed by mid 2010. Full factory tests will then be performed before the TBM is transported and assembled at the jobsite. Work on the access gallery is set to start in the fourth quarter of 2010.
Aker Wirth

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