Rockfall protection constructed for Inn power station

November 20, 2015 | Markus Lackner

By 2018, the third power station on the upper Inn will go into operation in the Swiss-Austrian border area. Felbermayr Special Civil Engineering was commissioned to carry out the rockfall protection works above the weir system in Nauders.

Before starting the work, it was necessary to secure the entire area as far as possible, so that the work could be carried out on the slope, comments construction manager Markus Winkler. For this purpose, boulders at risk of falling or loose were initially removed manually or by controlled explosion. "It was an enormous effort of some 6,000 working hours for our specially trained skilled workers," notes Winkler, who gave further specific details of the approximately 600 metres of securing anchors and 5,000 metres of safety cable installed in the wall. It was only after this that the geologist gave clearance for carrying out the rockfall protection construction on the 600 metre high rock face.

Challenging logistics

The actual work began in summer 2014 and was carried out in continuous operation, seven days a week. During this, up to twelve employees worked simultaneously on the wall. Even then the protection work and the logistics were a great challenge, as Winkler reports: "We could only access the hillside by foot, so all equipment and materials were transported to the rock face by helicopter." Overall, it amounted to around 400 tonnes of anchors, steel and securing materials, and for everything that could not be immediately installed, appropriate platforms had to be built on the steep terrain in advance. An immense task which could only be accomplished by applying great physical effort, with a high degree of skill and substantial safety awareness. As Winkler clearly points out, in admiration of the performance of his fellow employees, "One false move and there is no longer any grip". In total, 1,260 metres of six meter high protective fences were constructed by this method. This required approximately 800 anchor holes and installation of 5,000 metres of anchors. The constructed rockfall protection can firmly retain an impact load of 3,000 kilojoules, which Winkler describes impressively as, "equivalent to an eight tonne rock falling into the fence at a speed of 90 kilometres per hour".

By the end of September, the stabilisation works were sufficiently completed to be able to commence construction of the weir system.