Extreme gradient challenges in Switzerland 11 Apr 2013
Herrenknecht News Release
Successful breakthrough on the last of two challenging 40 degree hydro drives in Switzerland is complete for contractor Marti Tunnelbau and Herrenknecht.
The drive, using a 5.2m Herrenknecht gripper TBM, featured use of a new double anti-reverse lock mechanism developed by both companies especially for the project. The technology was developed as a vital safety measure to prevent slippage during the drive through Quinter limerock strengths of up to 120 MPa and under cover of up to 565m.
The machine drove two 1,030m-long headrace tunnels, connecting the underground machine hall cavern for the pump turbines to the upper reservoir some 600m higher, for the new pumped storage power plant at Limmern in Switzerland.

Gripper TBM utilises double anti-reverse lock mechanism to ensure safety on extreme gradient uphill drives

In both tunnels specialists from Marti Tunnelbau faced the additional challenge of passing through the Mortalbruch fault zone. Complex support and rock stabilisation measures slowed the advance but assured the final success of the project, part of the wider Linthal 2015 hydro project.
The immense gradient called for an extremely reliable safety concept to hold the machine securely in place during excavation. Slippage had to be avoided at all costs, and for the Linthal project Herrenknecht and Tunnelbau developed the double anti-reverse lock with full back-up redundancy of the available bracing levels of the 130m long and 800 tonne TBM. In all operating modes - advance, standstill or regripping - there were always at least two of the three locking systems independently bracing the machine against the sidewalls of the tunnel. The self locking mechanical system means that in the case of a power supply failure or a hydraulic failure the necessary bracing of the machine is assured at all times.
Breakthrough on the second headrace tunnel was achieved last month (13 March, 2013). Excavation of the first tunnel was completed in October 2011, 11 months after launch, with best performances of up to 130m/week. The TBM cutterhead was disassembled and the back-up pulled back through the pressure shaft and made ready to launch on the second drive. From February 2012 the TBM excavated the second tunnel, achieving a weekly best of 133m towards the end of the drive.
As part of the Linthal 2015 project the new Limmern pumped storage plant will raise capacity by 1,000 MW. Construction of the new power station is being carried out by the ARGE consortium Kraftwerk Limmern under the leadership of contractor Marti Tunnelbau. Linthal is expected to come online in 2015, and will be the largest hydro power facility in Switzerland.
Showcasing innovation at bauma

Herrenknecht has chosen bauma 2013 to showcase not only its existing technology, especially in the rapidly growing sector of underground urban transportation, but also its newly developed innovations for both mining and semi-trenchless shaft excavations.
Herrenknecht Boxhole Boring Machine

Herrenknecht Boxhole Boring Machine

Under the banner High-tech in Action, Herrenknecht will be demonstrating at its outdoor stand what it considers its most important innovations. These include the Pipe Express semi-trenchless system for the near surface laying of pipelines, as well as the newly developed Boxhole Boring Machine for the construction of production shafts in mining.
Visitors will be able to see how the Pipe Express system works for themselves as Herrenknecht has installed a 3m deep walk in shaft at its outdoor stand to assist demonstrations. The technology on view is nominated for the prestigious Bauma Machine Award, where it faces competition from two other companies including Aker Wirth with its Mobile Tunnel Miner for mechanised tunnelling in the mining sector.
Facing steep challenges on St Petersburg metro - TunnelTalk, August 2012
TBM giants dominate bauma 2013 awards - TunnelTalk, March 2013

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