In September, Robbins hailed as a success the second bore carried out by one of its TBMs using 19” back-loading disc cutters following breakthrough of the TBM on the Kops II headrace tunnel in Austria, (T&TI, July, p10).
The 5.54m diameter double shield TBM finished boring the 5.5km long headrace tunnel in late summer. The tunnel will supply water to the 450MW Kops II pump storage plant that is due to be finished in 2008.
T&TI understands the geology in the area to comprise amphibolite, hornblende schist, talus material and catacalcite.
Robbins said the 19” (face and gauge) cutters had been a good choice as the TBM bored through “challenging and mixed geology”. The TBM had previously been used on the Yellow River Project in China where it was equipped with 17” cutters.
Client Vorarlberger Illwerke AG awarded the contract for the plant to a JV comprising Swietelsky Tunnelbau GmbH, Torno SA and Torno Int. SpA. The JV rebuilt the TBM in China and Europe in association with Robbins GmbH who also supplied cutters, cutter rebuild services and technical assistance throughout the tunnel excavation.
Berhnard Sänger, general manager of Robbins GmbH, said: “The 19” gauge cutters performed excellently.” For the duration of the project, the cutter blockage ratio was only 2% compared to a more typical rate of 10-15%.
The Kops II tunnel will transport water from an upper reservoir to a surge tank leading to the power cavern. The new hydropower plant is required to provide increased output and reliability to the region’s power grid, which is struggling to meet peak load demands.
