Geomechanical features and landslide susceptibility of rock formations in northern Tuscany (Italy)

Several different geological formations crop out in the Northern Tuscany (Italy), where the geological, morpho-climatic and seismic characteristics determine high landslide susceptibility. This research particularly focuses on the Serchio River basin, where slope instability severely threatens population, villages and facilities. Geo-engineering survey and characterization with in situ and laboratory tests were performed, in order to define rock mass classification and geotechnical properties of the most widespread rocky formations cropping out in the basin, and assess their relationships with slope instability. Therefore, several properties were investigated, mainly referring to rock strength, structure, spacing and conditions of discontinuities, alteration. Field and laboratory tests were performed and included Schmidt Hammer Test, Point Load Strength Test and Unconfined Compressive Strength, aiming at defining the main rock and rock mass parameters. Then, the Bieniawski's Rock Mass Rating and the Hoek's Geological Strength Index were applied, in order to obtain an overall rock mass parameterization. Subsequently, the study area was classified and subdivided into several classes, mainly based on their physical-mechanical properties. This allowed to realize a GIS-based geotechnical map of the considered area, representing the areal distribution of the geotechnical properties of the classified rock formations. Finally, this map was compared with the landslide distribution of the area, in order to assess the landslide susceptibility of the considered formations.