Macro-micro bearing analysis of shallow footings on geogrid reinforced coral sands considering varied geogrid properties

The geogrid reinforced coral sand (GRCS) technique effectively stabilizes large-scale sites in island and coastal areas. This study develops a model test-based 3D discrete–continuous numerical model to investigate the macro–micro bearing behavior of shallow footings on reinforced coral sands, focusing on the effect of geogrid properties such as tensile strengths and node (rib) dimensions. Macroscopic bearing performance is improved with the enhanced geogrid properties, i.e., a maximum 141% increase in bearing capacity compared to the unreinforced condition. Microscopic mechanical analysis indicates enhanced geogrid properties impede stress transfer and particle movement, reducing geogrid buckling and foundation failure depth. The amount and spatial distribution of particle breakage in foundation soils depends on stress levels and particle displacements. These macro–micro bearing performances arise from stress difference and stress diffusion angle induced by geogrid properties. Given the uniform reinforcement mechanism under the influence of geogrid properties, a calculation method for the bearing capacity considering the stress difference and stress diffusion angle is proposed and validated against the numerical results. The presented study is of great significance for understanding the macro–micro bearing behavior and reinforcement mechanisms of shallow footings on geogrid reinforced coral sands.