Particle based method for shallow landslides: modeling sliding surface lubrication by rainfall

Landslides are a recurrent phenomenon in many regions of Italy: in par- ticular, the rain-induced shallow landslides represent a large percentage of this type of phenomenon, responsible of human life loss, destruction of assets and infrastruc- ture and other major economical losses. In this paper a theoretical computational mesoscopic model based on interacting particles has been developed to describe the features of a granular material along a slope. We use a Lagrangian method similar to molecular dynamic (MD) for the computation of the movement of particles after and during a rainfall. In order to model frictional forces, the MD method is complemented by additional conditions: the forces acting on a particle can cause its displacement if they exceed the static friction between them and the slope surface, based on the failure criterion of Mohr-Coulomb, and if the resulting speed is larger that a given threshold. Preliminary results are very satisfactory; in our simulations emerging phe- nomena such as fractures and detachments can be observed. In particular, the model reproduces well the energy and time distribution of avalanches, analogous to the observed Gutenberg-Richter and Omori distributions for earthquakes. These power laws are in general considered the signature of self-organizing phenomena. As in other models, this self organization is related to a large separation of time scales between rain events and landslide movements. The main advantage of these particle methods is given by the capability of following the trajectory of a single particle, possibly identifying its dynamical properties.