Integrating geomechanical surveys and remote sensing for sea cliff slope stability analysis: the Mt. Pucci case study (Italy)

An integrated approach to the geomechanical characterization of coastal sea cliffs was applied at Mt. Pucci (Gargano promontory, Southern Italy) by performing field-based geomechanical investigations and remote geostructural investigations via a terrestrial laser scanner (TLS). The consistency of the integrated techniques allowed to achieve a comprehensive and affordable characterization of the main joint sets on the sea cliff slope. The observed joint sets were considered to evaluate the proneness of the slope to rock failures by attributing safety factor (SF) values to the topple- and wedge-prone rock blocks under three combined or independent triggering conditions: (a) hydrostatic water pressures within the joints, (b) seismic action, and (c) strength reduction due to weathering of the joint surfaces. The combined action of weathering and water pressures within the joints was also considered, resulting in a significant decrease in the stability. Furthermore, remote survey analyses via InfraRed Thermography (IRT) and Ground Based Synthetic Aperture Radar Interferometry (GBInSAR) were performed to evaluate the role of the surveyed joint sets in inducing instabilities in the Mt. Pucci sea cliff. The results from the remote surveys: (i) GBInSAR monitoring revealed permanent displacements coupled to cyclic daily displacements, these last ones detected in certain sectors of the cliff wall; (ii) the thermal images allowed us to identify anomalies that correspond well to the main joints and to the slope material released due to recent collapses.