Numerical and experimental investigation of saturated granularcolumn collapse in air

Many hazardous natural phenomena like debris flows, avalanches and submerged landslides are governed by the interactions betweensolid grains and interstitial fluid. They display a complex interplay of physical mechanisms, which are still very challenging to simulatewith numerical methods. Different methods have been proposed in the literature to achieve this goal. This paper compares the results oftwo different numerical approaches: (i) a macromechanical continuum approach with the two-phase double-point Material PointMethod (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 granularcolumn collapses in a small-scale laboratory experiment, subsequently reproduced by the numerical codes. Unlike previous experimentsof collapse under gravity in dry or completely submerged conditions, in this paper the saturated material is released in air. These con-ditions better reproduce real natural onshore landslides and allows a discussion on the solid–fluid interaction.