A significant part of Italian mountain areas are covered by pyroclastic deposits resting at slopeangles higher than 40-50. The stability of these steep slopes in loose or poorly cemented pyroclastic materialsis essentially guaranteed by the positive effects of matrix suction on shear strength until an increase in saturation(and hence a decrease in suction) is induced by seepage initiated by different processes. The Cervinara flowslide(Campania,Italy) is a typical case where rainfall infiltration increased saturation and hence led to failure ofshallow pyroclastic deposits. At La Fossa Crater (Vulcano Island,north of Sicily,Italy) seepage induced bycondensation of vapor produced by the degassing activity of the active volcano seems instead to be correlatedto slope movements. In the paper the two case studies are examined by means of monitoring data,laboratoryinvestigations and numerical analyses.
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