A Lagrangian PFEM approach tothe numerical simulation of 3D large scale landslides impinging in water reservoirs

Landslides are exceptional natural hazards that can generate extensive damage to structures and infrastructures causing a large number of casualties. A particularly critical condition occurs when the landslide impinges in water reservoirs generating high waves. This work proposes a numerical tool to simulate the macroscopic behavior of a propagating landslide. The Particle Finite Element Method (PFEM) is here used and adapted to the specific case of landslide runout. The Lagrangian Navier-Stokes equations of incompressible fluids are used to describe the macroscopic landslide behavior. A rigid-visco-plastic law with a pressure dependent threshold, typical of a non-Newtonian, Bingham-like fluid, is used to characterize the constitutive behavior of the flowing material. Special attention is devoted to the definition of ad-hoc pressure-dependent slip boundary conditions at the interface between the flowing mass and the basal surface to better represent the real landslide-slope interaction. The proposed approach has been validated against numerical benchmarks and small scale experimental tests, showing a good agreement with the physical measurements. Real case scenarios have also been considered. 3D geometries of critical sites, where landslides have occurred, have been reconstructed allowing for the simulation of large scale real landslide runouts. Results are compared with post-event images and measurements, showing the accuracy and the capability of the method.