ABSTRACT
Unsaturated cohesionless or slightly-bonded pyroclastic materials can form relatively steep slopes whose stability suffers from wetting, which reduces suction and hence shear strength. The Cervinara flowslide was a typical rainwater-induced flowslide that occurred along a fairly regular slope formed by a primary deposit of unsaturated layered air-fall pyroclastites overlying fractured limestone. Since suction largely controls strength and hydraulic properties of the materials, a significant part of the testing program was carried out using apparatus especially suited to unsaturated soils. The complexity of infiltration process on unsaturated soils requires the use of a numerical model. The reliability of the model can be improved through a preliminary calibration and a validation through a back-analysis of in situ monitoring. Volcanic activity is essentially hydrothermal and concentrates at La Fossa edifice. Degassing is both concentrated at fumaroles or is diffused throughout the whole cone, favoured by the high permeability of the pyroclastic formations.
