An application of MIBSA to slow moving landslide

Large rockslides are characterized by complex spatial and temporal evolution, with non-linear displacement trends and significant effects of seasonal or occasional events. Forecasting landslide motion and collapse is a fundamental task for hazard zonation and the design of risk mitigation structures. Consequently, the analysis and modeling of the involved phenomena are very important. In order to forecast the landslide evolution in terms of displacement and natural risk it is necessary to simulate their mechanical behavior. For this reason, an evolution of the mathematical model MIBSA (Multi Interacting Block for Slope Analysis; Crosta et al. 2014; Dattola et al. 2016), consisting in a set of independent and interacting rigid blocks together with a viscous-plastic model based Perzyna’s approach, is here proposed. Block motion derives by solving the first momentum equation in which forces considered come from the interaction of blocks and the slip surfaces (shear band). The mathematical model for the shear was initially developed and calibrated on the experimental results on the sample from the Mont de La Saxe and obtained by means of the dynamic-loading ring-shear apparatus (DPRI-5, Sassa et al., 1997). This laboratory-testing machine has been used to simulate the entire process of failure. This model is applied to simulate three case studies: the Mont de La Saxe (Italy), Ruinon (Italy), and other large landslides under different boundary conditions. Since in the landslide case studies, the mass movement is strongly conditioned by the seasonal trends of the groundwater table, their piezometric surfaces are reconstructed by the previous in situ measurements using an interpolation tool directly implemented in the numerical code. Finally, the simulations give insight about the progressive failure mechanism involved in the evolution of the rockslide. The numerical simulations give the evolution of the kinematic variables (displacement, velocity and acceleration) of each block as well as global and local safety factor to provide a basic tool for the prevision of local and/or global instabilities.