Soil hydraulic behaviour of a selected benchmark soil involved in the landslide of Sarno 1998

A multidisciplinary approach was adopted in this paper in order to study the very complex and unpredictable phenomenon of rainfall-triggered landslides. Physical and chemical measurements were made on a selected benchmark soil involved in the landslide of Sarno (southern Italy) in May 1998. Water behaviour inside the soil covering a typical slope of the area was simulated using a two-dimensional simulation model. Sensitivity analyses of the model showed that a few uncertainties regarding input data (climatic and physical) can be accepted without substantially changing output data, namely soil water storage values. The effects of the interruption of the pedological continuity of the slope were simulated in terms of total weight encumbering the bottom of the soil stratification just behind a section of discontinuity. There resulted an increase of more than 30% in soil water storage with respect to the same section of the undisturbed slope. It causes an overloading which produces the same values of soil tangential pressure as those of peak strength measured by direct shear tests. Notwithstanding the simplifications introduced to carry out this study, the proposed approach demonstrates the possibility of quantifying the consequences of some human or natural changes regarding soil-covered slopes and hence the potential of improving landslide risk assessment.