Analysis of deformations occurring at the edge of a rock cliff underneath a historical center

The gate of the ancient town of S.Leo is located at the edge of an overhanging rock cliff, over 60 m high, consisting of calcarenites with siltstone beds. The cliff borders a rock butte overlying a tectonized clay substratum. Both the rock slab and the substratum are characterized by a structural complexity at different scales. A comprehensive analysis of numerical models and of in situ surveys and monitoring results suggest that the upper part of the cliff is affected by deformations, which can be seen as a part of a flexural toppling mechanism. At present the instability phenomenon is characterized by small but continuous deformations. Despite its slow rate, which is also due to the remedial measures carried out during the last years, its evolution has to be carefully monitored. The structural integrity of the ancient buildings is in fact to be preserved, and the long term effects of the severe state of stress induced by the morphological conditions can not be underestimated.