Characterization of Clayey Landslides Using Multidisciplinary and Multiscale Dataset

Slow-moving landslides frequently affect gentle slopes made of clayey formations, with volumes which can range from a few m3 to several tens of millions of m3. These landslides frequently exhibit sudden acceleration phases and flows, which can be triggered by changes in the stress field or modifications in the soil characteristics. We present here an integration of multidisciplinary and multiscale data. The combined interpretation of continuous geophysical data acquired over the whole Avignonet landslide (OMIV observatory on landslides in the French western Alps) with punctual measurements (boreholes and geotechnical tests) allowed building a robust 3D morpho-structural model of the slide down to a depth of around 300 m. It has been possible to characterize the main lithological features along with the location of slip surfaces. We propose here that, in complement with shear-wave velocity which gives information on the mechanical effect of the slide, resistivity variation observed at sub-surface can be linked to grain size variation which seems to partially control the landslide kinematics via the regulation of overpressure. Combining geophysical data allows to take into account both lithological variations and landslide activity to account for surface displacements.