Three-Dimensional Discrete-Element-Method Analysis of Behavior of Geogrid-Reinforced Sand Foundations under Strip Footing

This paper presents a three-dimensional discrete numerical analysis associated with the interaction of geogrid and surrounding soils in geogrid-reinforced sand foundations under strip footing. After validating the numerical simulations with experimental results, the model was then employed to examine the deformation behaviors, contact force network, energy dissipation mechanism, and response of the geogrid. Additional analysis was also carried out to understand the effect of geogrid layout parameters on the bearing capacity of foundations and progressive failure of reinforcements. The results showed that the inclusion of geogrid layers spaced at 0.25B (B = footing width) inhibits the horizontal displacement of soils in the reinforced zone, whereas facilitates the displacement field in the underlying unreinforced zone and consequently results in an upward tensile failure of reinforcements. The progressive failure of reinforcements induces fluctuations of the loading–displacement curve in the postpeak regime. Punching shear failure initially develops in the reinforced zone in terms of force chains developing directly beneath the footing. With footing settlement increasing, the failure mode is characterized by a punching failure with a diffusion angle developing in the reinforced zone, followed by a general shear failure in the underlying unreinforced zone. Furthermore, the progressive failure of geogrid layers is associated with reinforcement spacing and number of reinforcement layers, rather than reinforcement length. A larger reinforcement spacing and a higher number of reinforcement layers tend to induce a downward fracture failure.