A DEM study of the effect of the loss of fine particles on the mechanical behavior of gap-graded soils

Abstract

Modeling of suffusion in granular soils by using a fully coupled fluid-DEM model is still challenging due to its very high cost of computation. The particle removal approach is an alternative to mimic the erosion of fine particles by the seepage flow. In this paper, we study different particle removal methods and their impact on the mechanical behavior of eroded samples. Gap-graded samples with different fine contents fc were simulated by using the DEM. Fine particles are removed from the original sample under constant stress state by using three different methods: random removal, the method of Scholtès et al. based on the particle internal moment mp, and a new method proposed here that is based on the concept of weak and strong force networks. A micro-mechanical investigation into numerical samples shows that the fine particles have small contribution in carrying stresses when fc≤30% but they offer a great bracing effect to the coarse fraction, which allows the latter to carry high stresses. As a result, a removal of fine particles destroys greatly this bracing system, leading to a great reduction in the bearing capability of the coarse fraction. A comparison between the three methods shows that a removal of fine particles belonging to the weak force network has a lower impact on the mechanical behavior of eroded samples than the random removal. In addition, the method of Scholtès et al. gives results quite similar to those given by the random removal in terms of the shear strength of eroded samples.