Reinforcing soil beneath foundations is one of the standard methods to improve the foundation performance. However, soil relative density may affect the efficiency of reinforcement. This experimental study has been conducted on a model ring foundation resting on medium, dense, and very dense geogrid-reinforced sand. For this purpose, 17 tests were carried out to evaluate the effect of soil density and reinforcement depth and size on bearing capacity and settlement of the ring foundation and its normal contact pressure distribution. The results show that geogrid-reinforced sand with higher relative densities improves bearing capacity and decreases settlements significantly. It can be shown that implementing a geogrid layer that is equal to the dimensions of the footing is cost-effective. The scale effect analysis has been conducted for the model foundation, sand, and geogrid used in this research. Additionally, normal contact pressure distributions for unreinforced and reinforced sand are presented. Decreasing the depth of reinforcement transforms the form of normal contact pressure distribution from saddle to parabolic.

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