Analysis of a steep slope in unsaturated pyroclastic soils

This paper regards the properties of unsaturated pyroclastic soils involved in a shallow instability phenomenon in a cut slope. The slope is located along the road connecting the urban area of Naples to the Pozzuoli suburb (10-km west from Naples, Italy). A complete analysis of stability in steep unsaturated soil slopes requires the knowledge of the relationship between the shear strength, matric suction and rainfall. Therefore mechanical and hydraulic behaviour of soil involved has been investigated through extensive laboratory activities. The main aim of this investigation is to define shear strength characteristics as well as to establish the relationship between shear strength and water content (or suction). Slope stability is then evaluated with a simple approach that accounts for the contribution of suction to shear strength.