ABSTRACT:

On January 1996, a landslide of rocks mixed with debris interrupted traffic flow on the road in Germanasca Valley. The landslide occurred in an area, of average seismic activity, comprising micaschists of the Dora-Maira Complex. The aim of the paper is to present two continuous monitoring systems capable of sending light alerting signals to stop the road traffic, since numerical modeling highlighted the inadequate safety provided by the retaining nets installed on the landslide debris cone. The work highlights the risk for the viability in relation to the geomorphological and geo-structural characteristics as well as the nonfeasibility of other protective structures. To identify the optimal sites for the monitoring systems in the landslide area, topographical, photogrammetrical, geo-structural surveys and numerical modeling have been carried out.

INTRODUCTION

On January 15, 1996, a landslide of rocks mixed with debris occurred in Germanasca Valley (Italian Western Alps, Figure 1) near the village of Pomeifrè and near the Fontane mine, famous worldwide for the excellent quality of its talc and of great importance for the local economy. The rockfall (over 10000 m3 in volume) occurred on the left side of the slope at 1125 m a.s.l.: landslide toe was 70 m wide and stopped at 990 m. The debris covered a busy road used by the trucks servicing the close mine and by the tourists directed to a ski resort. Consequently, three orders of retaining nets were installed on the landslide debris. Previous rockfall had occurred at the same site (1974) and continued debris falls on the road required the need to study additional slope protective methods in order to ensure viability safety. To the West of 1996 landslide area, intensely fractured rock masses with open discontinuities and large boulders sitting on the bedrock were surveyed.

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