Geophysical characterisation of a rockslide in an alpine region

A combination of geophysical methods has been used for the characterisation of a rockslide area, located in the Graie Alps, NW of Italy, where the construction of a roadway tunnel has been planned. Electrical resistivity tomography (ERT), seismic refraction tomography (SRT) and spectral analysis of surface waves (SWM) have been adopted to determine the overburden thickness and the geometry of the sliding surfaces. The geomechanical characterisation of rock mass was performed by means of horizontal seismic profiles (HSP) and sonic log in a horizontal borehole. The results have been calibrated by comparing the geophysical responses with the geological evidence derived from boreholes and with the movements recorded using inclinometric probe. Moreover, borehole geophysics results were validated by the results of laboratory measurements performed on core samples. The integration of geophysical and geotechnical results allowed the definition of a subsoil model for the investigated area and provided the necessary data for the design of the roadway tunnel. The study shows that surface and borehole geophysical techniques could be an efficient and cost-effective tool in rockslide investigations.