A numerical experiment of backward erosion piping: kinematics and micromechanics

We report on a numerical experiment by which we investigated the propagation of an erosion pipe in a water saturated granular soil. The simulation was performed with a two-dimensional implementation of the coupling between the discrete element method and the lattice Boltzmann method. A synopsis of the numerical scheme is provided. The specimen and testing conditions were designed as representative of the pipe front region.The kinematics of mobilisation and fluidisation of the granular mass were investigated based on the physically-motivated definition of particle velocity thresholds. We measured a constant mass erosion rate, up to a clogging event. The study includes a micromechanical analysis of the response of the granular skeleton. We emphasise the influence of the unloading-induced damage on the erosion path, and the relevance of force chain arching as a self-organised resistance mechanism.