3D geological model of the San Leo plateau

The town of San Leo, situated in the Northern Apennines in Italy, is subject to instability phenomena due to its particular geological nature, described as a highly fractured calcarenite slab embedded in clay-rich terrains. The 3D geological model of the San Leo plateau, comprehending the eastern zone of the rock slab, was developed through the integration of data obtained from laser scanning and photogrammetrical surveys, as well as surface and core drilling geomechanical surveys, into one single system that enables the visualization of all structural features of the plateau in association with one another, including superficial and in-depth fractures and the equipment from the monitoring system that surveils the rock mass behavior. In that manner, it was established that the area along the northeastern scarp formed by the 2014 landslide event is highly fractured, characterized by an extremely high number of closed and few open fractures, whereas the area surrounding the road to the San Leo fortress along the eastern cliffs present fewer fractures in general, located predominantly in the vicinity of the eastern lateral walls. Moreover, two possible collapse scenarios were evaluated in the northeastern cliffs, in which the failure mechanism corresponding to the 2014 event was emulated for fractures parallel to the scarp, resulting in the collapse of a rock volume equivalent to 428,913.804m3. The persistence and behavior of the fractures involved in these scenarios were also analyzed, indicating that such events are not imminent at the present time.