Geogrid-soil interface characteristics are essential in designing mechanically stabilised earth walls, reinforced soil slopes, etc. While experimental pullout tests are commonly conducted but it falls short in capturing the micromechanical response. This study employs the 3D Discrete element method (DEM) to simulate the pullout test with biaxial geogrids after validation against the previously reported experimental results.This study primarily focuses on the effect of particle size distribution (PSD), considering both monodisperse and polydisperse systems (well and poorly graded), normal stress, porosity and displacement rates. It was observed that the monodisperse system shows weaker force chains with relatively less particle rotations, resulting in least pullout resistance at macro level when compared against the other two configurations. However, when particle gradations in polydisperse systems are compared, well graded particle assembly shows strong force chain networks than poorly graded which results into maximum pull-out resistance at the same pullout displacement. These findings provide valuable micromechanical insights into the underlying role of PSD in optimizing the geogrid-reinforced systems.
Khandelwal et al. (2025) studied this question.