Two-dimensional discrete element models of debris avalanches: Parameterization and the reproducibility of experimental results

Application of the discrete element method (DEM) to model avalanches of granular materials requires determining the correct geometric and rheological parameters for and between the particles as well as for the basal surface. The use of spherical (circular in 2-D) particles enhances particle rolling, yielding excessive runout values. The solution usually adopted to correct this effect is to introduce a drag force which artificially slows down the particle velocities. The aim of this study is to test the capability of the DEM to simulate well-controlled unsteady channelized granular flows, considering the measured properties of the particles and of the basal surface which naturally contribute to dissipate energy. We first performed a parametrical analysis on a simple 2-D model in order to estimate the influence of particle shape, friction parameters, and restitution coefficients on the dynamics of the flow and on the deposit geometry. We then simulated three channelized laboratory experiments performed with two materials and two bed linings. Using the geometrical layout and the values of the mechanical parameters provided by the authors, we obtained a remarkable agreement between the observed and 2-D simulated deposit shapes for the three experiments. Also, the computed mass evolution with time was very consistent with the experimental snapshots in all cases. These results highlight the capability of the DEM technique for modeling avalanche of granular material when the particle shape as well as the friction and restitution coefficients are properly considered.