Rock Avalanche Investigation in Tempi Valley, Greece
GRAF K., RATHMAYR B., RAEMY V. (2015)
G. Lollino et al. (eds.), Engineering Geology for Society and Territory – Volume 2, DOI: 10.1007/978-3-319-09057-3_365, © Springer International Publishing Switzerland 2015
On December 17th 2009, a rock avalanche with a total volume of about 500 m3 occurred after heavy rainfall near the western entrance of Tempi Valley, Greece. The road was hit by rocks and boulders with a single maximum size of about 20 m3 causing one fatality. A close up inspection showed that dissected and toppled rock fragments had collapsed 100 m above the road. Apart from the tectonic predisposition, possible triggers were the absorption of infiltrating water in open joints, the possible hydraulic head in closed cracks during rain fall and the lowering of the friction angle of the material (earthfill) in the slide plane during rain storm. First response measures were carried out to secure the critical section of the rockfall incident. An instable rock mass was monitored and stabilized directly with high tensile steel netting and an adequate amount of rock bolts. Step by step, measures were then deployed from top to bottom of the site: Scaling of the uppermost transition zone, installation of a low energy barrier followed by scaling of the steep transit zone and finally scaling of the lowermost slope zone. As a permanent and long term protection measure, a rockfall barrier was built above the road. Now regular inspections are carried out on the slopes.