Comportamento dei terreni argillosi e stabilita dei versanti in formazioni strutturalmente complesse

Landslides in structurally complex clay formations are widespread in the Italian Apennines and prevail over other types of landslides in the Basento river valley. Based on data collected in the Basilicata region, this paper analyses some kinematic, hydraulic and chemo-physical aspects of the landslide behaviour that are considered interesting for risk mitigation. The paper is divided into three parts. After a brief overview of the lithological and landslide typologies of the Basento valley, in the first part, the paper focuses on a large slope affected by various landslide systems, and describes the main kinematic characteristics of some landslides, highlighting the fast response of deep basal displacements to rainfall. In the second part, based on piezometric measurements, permeability tests and numerical simulations, the observed behaviour is attributed to the intense and rapid effects of rainfall on the water pressures along the slip surface that, in turn, are justified by the permeability of the zone, higher than those of the landslide body and stable formation. The influence of the hydraulic features on the efficiency of drain systems is shown to be significant. In the third part, the composition of the pore water is analysed as well as the effects of its variations on the behaviour of the clays and the landslides. In particular, the effects of the soil mechanical deterioration induced by the chemo-physical interaction with rainwater are shown and their influence on the landslide behaviour is discussed.