The Randazzo landslide (Peloritani Mounts – Sicily NE): Geomorphological and Hydrogeological studies on the structurally complex formations

This work presents the results of further researches carried out on a landslide which took place in the Randazzo area (Mt. Peloritani-Sicily N-E) in March 1996 and obstructed Alcantara riverbed and cut off a main road (S.S. 116) along about one kilometre length, between the towns of Randazzo and S. Domenica Vittoria. The slope involved is made up of Mt. Soro Flysch and Varicoloured Clays; these are structurally complex formations due to the strong deformations which followed the tectonic events. These conditions are reflected on the mechanical behaviour of the soils, whose unstable structure is emphasised by cyclic desiccation and saturation processes. At the landslide embankment, the difference between the upper sandstone permeability and the lower clay layers one caused an outlet of groundwater which can be classified as springs due to undefined permeability boundary. The failure started due to both the particular rainfall during the months before the event and the arenaceous aquifer power of storing considerable water volumes continuously released to the formation below, thus establishing critical hydrodynamic conditions that destroyed the residual soil resistance. For a better understanding of the landslide kinematics and evolution, useful elements have been carried out by boring and monitoring the landslide during its further evolution. On the basis of laboratory analysis carried out for undisturbed soil samples, physical and mechanical characteristics of the formations involved in the landslide have been determined.