Giuseppe Sorbino

Modeling of Rainfall-Induced Shallow Landslides of the Flow-Type

The paper deals with the modeling of failure and postfailure stage of shallow landslides of the flow-type that often affect natural shallow deposits of colluvial, weathered, and pyroclastic origin. The failure stage is frequently associated to rainfall that directly infiltrates the slope surface and to spring from the underlying bedrock. The postfailure stage is characterized by the sudden acceleration of the failed mass. The geomechanical modeling of both stages, based on site conditions and soil mechanical behavior, represents a fundamental issue to properly assess the failure conditions and recognize the potential for long travel distances of the failed soil masses. To this aim, in this paper, the current literature on the failure and postfailure stages of the shallow landslides of the flow-type is first reviewed. Then, an approach for their geomechanical modeling is proposed and three different modeling alternatives are presented. These models are then used to analyze, at different scales, a relevant case study of Southern Italy Sarno-Quindici event, May 4-5, 1998. Numerical analyses outline that both site conditions and hydraulic boundary conditions are among the key factors to evaluate the reliability of landslides of the flow-type. The potentialities and limitations of the available models are also evidenced as well as the perspectives related to the use of more advanced numerical models.

Application of a SPH depth-integrated model to landslide run-out analysis

Hazard and risk assessment of landslides with potentially long run-out is becoming more and more important. Numerical tools exploiting different constitutive models, initial data and numerical solution techniques are important for making the expert’s assessment more objective, even though they cannot substitute for the expert’s understanding of the site-specific conditions and the involved processes. This paper presents a depth-integrated model accounting for pore water pressure dissipation and applications both to real events and problems for which analytical solutions exist. The main ingredients are: (i) The mathematical model, which includes pore pressure dissipation as an additional equation. This makes possible to model flowslide problems with a high mobility at the beginning, the landslide mass coming to rest once pore water pressures dissipate. (ii) The rheological models describing basal friction: Bingham, frictional, Voellmy and cohesive-frictional viscous models. (iii) We have implemented simple erosion laws, providing a comparison between the approaches of Egashira, Hungr and Blanc. (iv) We propose a Lagrangian SPH model to discretize the equations, including pore water pressure information associated to the moving SPH nodes.

Seasonal effects of rainfall on the shallow pyroclastic deposits of the Campania region (southern Italy)

The shallow deposits of unsaturated pyroclastic soils covering the slopes in the Campania region (southern Italy) are systematically affected by various rainfall-induced slope instabilities. The type and triggering of these instabilities depend on several factors, among which in situ soil suction—as an initial condition—and rainfall—as a boundary condition—play a fundamental role. Based on the available database—which includes a comprehensive catalogue of historical data, in situ soil suction measurements and soil laboratory tests along with the results of geomechanical analyses—this paper discusses the relationships among in situ soil suction and rainfall conditions and induced slope instability types. The goal is to reach a better understanding of past events and gain further insight into the analysis and forecasting of future events. In particular, the paper outlines how the season strongly affects the spatial distribution and the type of slope instability likely to develop. For example, erosion phenomena essentially occur at the end of the dry season and originate hyperconcentrated flows while first-time shallow slides prevail in the rainy season and later propagate as debris flows or as debris avalanches.