Mechanics and velocity of the Lärchberg–Galgenwald landslide (Austria)

The Lärchberg–Galgenwald landslide in Austria is situated in the south western slope of the Rantenbach valley, 2 km upstream of the town of Murau. The slope is made up of marbles some 300 m thick lying on a phyllite base some 140 m thick. The cracks of the main scarp, which are some 10 m wide, are monitored by wire extensometers and are opening with a precipitation dependent velocity of 30 cm per year. Numerical analyses showed that an overall volume of up to 10 000 000 m3 might bury the road in the valley and dam up the Rantenbach River, causing a debris flow. igations of the risks of the scenarios and of the costs of mitigation measures have shown that sealing of the surfaces of the roadways, drainage and diversion of precipitation and the realization of a watershed management project are highly economical. cavation of a by-pass tunnel for the Rantenbach river in the opposite slope, as well as a toe weight at the bottom of the slope in connection with a covered tunnel for the Rantenbach River, appear not to be economical from the present point of view.