Numerical and experimental investigation of saturated granular column collapse in air

Many hazardous natural phenomena like debris flows, avalanches and submerged landslides are governed by the interactions between solid grains and interstitial fluid. They display a complex interplay of physical mechanisms, which are still very challenging to simulate with numerical methods. Different methods have been proposed in the literature to achieve this goal. This paper compares the results of two different numerical approaches: (i) a macromechanical continuum approach with the two-phase double-point Material Point Method (MPM) and (ii) a micromechanical approach with Discrete Element Method coupled with the Lattice Boltzmann Method (DEM-LBM). With the objective of highlighting potentialities and critical points of the two approaches, we conduct saturated granular column collapses in a small-scale laboratory experiment, subsequently reproduced by the numerical codes. Unlike previous experiments of collapse under gravity in dry or completely submerged conditions, in this paper the saturated material is released in air. These conditions better reproduce real natural onshore landslides and allows a discussion on the solid–fluid interaction.