A 3D-DEM investigation on the effect of initial anisotropy in granular soils mixed with varying fines content

The Discrete Element Method (DEM) is employed to simulate the constant-volume triaxial compression (TXC) and triaxial extension (TXE) experiments on the initially anisotropic coarse-fines particulate mixtures containing fines contents (FCs) ranging from zero to 40%. This study investigates the impact of FC on the evolution of five anisotropy variables expressed in terms of the particles’ long axes, contact normals, branch vectors, normal contact forces, and tangential contact forces in the coarse-fines mixtures. An increase in FC is found to reduce the impact of initial anisotropy. Through partitioning contacts into coarse-coarse, coarse–fine, and fine-fine categories, the participation of fines in strong force networks of the assemblies is determined. Accordingly, a micro-scale fines participation factor is defined to quantify the active participation of fines in the load-carrying microstructure of the mixtures. The critical state values of this factor are then compared to the corresponding back-calculated macro-scale phenomenological measurements.