Geosynthetic materials are crucial for reinforcing soil above subterranean voids. However, the complexities of load transfer mechanisms in reinforced structures remain elusive. This study investigates the deformation and failure mechanisms in geogrid-reinforced soil using trapdoor experiments. The particle image velocimetry (PIV) technique was utilized for detailed observation of soil deformation, while fiber optic strain sensing cables were used to monitor tensile strains within geogrids. Results indicate that soil arching redistributes loads across the trapdoor area, effectively transferring loads from subsiding to adjacent stable regions. As trapdoor displacement increases, the initial soil arch collapses, prompting the formation of another stable arch. This cycle of development and failure of soil arch continues until shear bands reach the ground surface. Soil arches are more prone to failure over shallower voids. Strain data reveal that the geogrid's tension varies with the tensile strain and is highest near the void's edges. For shallow voids, the tensioned membrane effect of the geogrid bears more of the overlying soil weight, whereas for deeper voids, soil arching plays a more significant role in load transfer. This study provides important insights into the interaction between soil arching and tensioned membrane effects, offering potential implications for optimizing geosynthetic design.