Continuum description of flow-like landslide dynamics

Landslide run-out is a complex phenomenon, much more difficult to simulate by models than flow of fluids. The main complicating aspects concern that landslide material is often heterogeneous and its characteristics may change during the landslide movement due to drainage, hydraulic interaction between fluid and grains, comminution of grains or mixing with surface water or partly or fully liquefied superficial material entrained from the path. The continuum mechanical theory, treating the heterogeneous and multiphase moving mass as a continuum, has emerged in the last years as a useful tool for describing the evolving geometry and the velocity distribution of a mass flowing down a surface. A hypothetical material, “equivalent fluid”, whose rheology is controlled by a small number of parameters is, in fact, introduced to represent the bulk behaviour of a landslide. After a brief introduction on landslide characteristics and dynamics, new advances in the continuum mechanical description of flow-like landslides are discussed in dedicated sections. Each section deals with one of the main aspects that characterize the physical behaviour of a landslide and presents the simplifying, but nevertheless realistic, assumptions made to streamline their mathematical formulation. The mathematical formulation is then implemented in a numerical code (RASH3D) to test the capability of each mathematical assumption in allowing the reproduction of real phenomena dynamics. Results of numerical simulations of laboratory tests and real events are discussed in this chapter to this aim.