Discrete element study on the mechanical properties of geogrid-sand interface in large-scale direct shear test

Purpose To quantify and comprehend the micro-scale interactions and underlying particle-scale mechanical behavior that govern the reinforcing mechanism of geogrids in sand. Design/methodology/approach The study utilizes a two-dimensional discrete element method to simulate a large-scale direct shear process. The approach analyzes the evolution of macroscopic and microscopic mechanical properties at the geogrid-soil interface, specifically tracking particle contact states, distribution states and particle movements under varying shear displacements. Findings Maximum deformation occurs above the geogrid near the model's left boundary, with the vertical strip's deformation opposing the shear direction. Both experimental and numerical results demonstrate that interparticle contact force correlates with the distance from the geogrid. Furthermore, particle movement at the interface governs the sample's shear dilation: particles near the geogrid primarily rotate, while those farther away mainly undergo translational motion. Sand particles in the lower shear box exhibit stress concentration and compaction, whereas particles in the upper shear box loosen. Originality/value This research provides a fundamental theoretical basis for an in-depth understanding of the complex microscopic shear behaviors and mechanical dynamics at the geogrid-sand interface.