An integrated geological, geotechnical and geophysical approach to identify predisposing factors for flowslide occurrence

This study combines geological, geotechnical and geophysical analyses to construct a 3D model of the subsoil, based on a significant amount of data collected at a test site in the Lattari mountain range in southern Italy. Several investigation techniques were applied to study the spatial variability of the local stratigraphic setting and relevant geophysical and geotechnical parameters at the slope scale. By integrating field and laboratory measurements, such as geological logs, soil sampling, 2D and 3D electrical resistivity tomography surveys, time domain reflectometry profiles and characteristic curves of electrical resistivity vs saturation degree, the continuous stratigraphy of the pyroclastic cover in question was reconstructed and 3D models of effective saturation degree in different pyroclastic horizons were retrieved. As the proposed procedure is applied to study flowslide initiation, the test site was implemented on a 32° slope affected by historical flowslides. The following factors predisposing to flowslides were identified: steep stratigraphic contact between shallower soils and bedrock, impermeable layers that buffer the draining of the fractured limestone, preferential rainwater infiltration paths, and spatial distribution of water content in the soil.