Heavy rainfalls in late 2002 reactivated an ancient deep-seated landslide in the Varrone valley (Northern Italy). the unstable body threatens a hydroelectric power plant as well as a new industrial district placed along the valley line. Though the sliding surface is believed to be deeper than 100m, landslide reactivation concerned just a shallow portion of the slope close to the landslide toe. A detailed geological survey was undertaken after the events in 2002. inclinometers and piezometers were deployed in some boreholes, which were also used to assess rock layering and quality, along with the presence of discontinuities and of groundwater. to this final aim a preliminary Electrical Resistivity Tomography survey was also carried out. Recently, geophysical surveys were performed in order to validate geological assumptions and to assess the condition of the slope over a wider area. Ground penetrating radar profiles helped to determine the dip as well as the persistence of the discontinuities that are considered preferential paths for groundwater flow. A combined P- and S-wave refraction survey delineated the interface between shallow glacial sediments and underlying gneiss layer, and was used to infer elastic parameters of the subsurface. the outputs of the geophysical surveys were used to run a numerical model with the aim of evaluating the kinematics of the slide, possible future scenarios and the associated mitigation measures.


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