Micromechanical Analysis of Detachment Mechanisms of Suffusion

Abstract

Suffusion is a typical phenomenon of seepage-induced internal erosion, corresponding to fine particles erosion from the coarse matrix under the action of a fluid. A three-dimensional and spatially resolved fluid-solid coupling method based on lattice Boltzmann method (LBM) and discrete element method (DEM) is proposed to simulate suffusion in binary mixtures under anisotropic stress states. Based on such numerical simulations, eroded grains are identified and the mean squared displacement as well as the ratio between drag force and contact force of these eroded particles are computed to describe the detachment mechanism. The results show that the fluid force acting on eroded particles increases in the simulation which corresponding to the steep slope in squared displacements. Regardless of the initial state, the ratio between the fluid force and the contact force of the eroded particles displays a downward trend over time, reflecting the gradual dominance of the fluid force, which eventually leads to particle detachment and erosion. Based on the judgment between the direction of the fluid force and the direction of the contact force, a contact index P is then proposed to determine whether the contact is going to slide or strengthen under the action of the fluid. The distribution of indexes P for the contacts of eroded particles just prior to their detachment reflects that fluid induced sliding dominates. A particle detachment index is thus proposed and the overall detachment sensitivity of the binary samples is eventually investigated with respect to the fluid flow direction.

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