Landslides affecting tabular rocks in complex geological situations: the case of Sasso di Simone and Simoncello (Northern Apennines, Italy)

In the Northern Apennines, the geological situations due to the superimposition of competent rocks on argillaceous and shaly clay substrata are particularly widespread and give rise to complex and prolonged mass movements. To these situations, the case of Sasso di Simone and Simoncello is ascribable. Due to the intense tectonic stresses which have accompanied the orogenesis of the Apennine chain, these competent tabular-shaped cliffs are affected by widespread fractures whose nature and distribution directly influence the evolution of the slope movements. The latter are not confined to the lithic rocks, but extend also to the clayey substratum, which is also highly tectonised, thus causing complex landslides, prevalently showing lateral spreading deformations, concentrated along the cliff margins. The main cause of the persistent slope instability is identified with the high erodibility and deformability of the clayey soils, of which a basic geotechnical classification is given.