1 Introduction

Large rockslides are characterized by complex spatial and temporal evolution, with non-linear displacement trends and significant effects of seasonal or occasional events. Forecasting landslide motion and collapse is a fundamental task for hazard zonation and the design of risk mitigation structures. Consequently, the analysis and modeling of the involved phenomena are very important.

One of the most deeply investigated landslides of the whole Alpine arc is Mont de La Saxe landslide (Fig. 1), located within a deep-seated gravitational slope deformation (DSGSD). This landslide is located at the upper part of the Aosta Valley, NW Italy. The rock slide dimension is of about 8x106 m3, extends between 1400 and 1870 m a.s.l., over an area of 150'000 m2 with a horizontal length of about 550, maximum width of 420 m, and average slope gradient of 37°.

The area is subjected to snow fall during the winter (average equivalent rainfall 810 mm ca., data— Mont de La Saxe meteo station at 2,076 m a.s.l.) with a total average precipitation of about 1,470 mm (at the rock slide crown area) and a real evapo-transpiration of about 370 mm.

Aim of this work consists in analyzing this instability by means of an experimental campaign and numerical modelling. The target of this analysis consists in forecasting the landslide displacement and the possible failure.

2 Experimental tests

The samples used for experimental tests derived by full core recovery are characterized by a metasedimentary sequence. The petrographic characterization have been performed by XRD (X-Ray Diffraction), XRF (X-Ray Refraction) and SEM (Scanning Electron Microscope) with microprobe in addition to laboratory tests on samples from shear zones. Samples from shear zones have different characteristics in terms of thickness of the shear zone, grain size, mineral composition and weathering.

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