Pull-out interface mechanism of geogrid-reinforced construction and demolition waste

To investigate the interaction mechanism between geogrids and construction and demolition waste (CDW), this study established particle models of CDW and structural models of geogrids based on the discrete element method. By simulating the pull-out process of geogrids embedded in CDW, the displacement and force characteristics of CDW were analyzed, and the evolution of force chains at the reinforced interface was investigated to elucidate the interfacial interaction and load transfer mechanisms. The results revealed that, under pull-out loading, the displacement of CDW particles gradually propagated from the front region to the middle and rear regions, with an expanding disturbance zone accompanied by particle rearrangement and void filling. Particle movement was governed by both geogrid-particle interaction forces and inter-particle forces, with the former dominating the instantaneous response, while the latter controlled the progressive accumulation of displacement. As the pull-out displacement increased, the interfacial force structure continuously adjusted, accompanied by a redistribution of force transmission paths. Compared with biaxial geogrids, triaxial geogrids, due to their multidirectional confinement, were more capable of forming stable interlocking with particles, thereby exhibiting higher pull-out resistance.