Stabilizing role of coarse grains in cohesionless overfilled binary mixtures: A DEM investigation

Cohesionless binary mixtures are commonly encountered in nature and frequently used as filling materials in geotechnical engineering. It is known that coarse grains have a reinforcement effect on overfilled binary mixtures in which coarse grains are embedded in the matrix of fine-grains. However, the micromechanical origin of this reinforcement effect remains unknown. Using 2D discrete element method (DEM) simulations, this study aims at highlighting the impact of coarse grains on the geometrical fabric and mechanical state of cohesionless overfilled binary mixtures. We show that coarse grains contribute to the stability of cohesionless overfilled binary mixtures by limiting macroscopic plastic deformation. Coarse grains play the role of attractors of force chains, as they promote more connected contact force networks in overfilled binary mixtures. The results of micromechanical analyses further show that embedded coarse grains in overfilled binary mixtures have a long-range influence in the surrounding fine-grain matrix in the form of a "fine bridge," which enables better stress transmission and improves the bearing capacity of the mixture.