Performance assessment of footings on geogrid-reinforced manufactured sand and river sand beds

Abstract

Owing to the rapid growth of construction activities, particularly in urban areas, the availability of suitable land for construction is steadily decreasing. Consequently, reinforced soil foundation systems are increasingly being adopted. Additionally, the depletion of natural river sand has led to its limited availability, prompting the need for alternative materials such as manufactured sand (M-sand). This study investigates the performance of circular and square model footings resting on reinforced M-sand and river sand beds under static loading conditions. Experimental tests were conducted on both sand types by varying key parameters such as relative density (30% and 50%), number of reinforcement layers (1-5), spacing between the reinforcement layers (0.3B, 0.4B and 0.5B), and footing shape. The results indicated a significant increase in the bearing capacity compared to unreinforced sand beds. The bearing pressure increased with an increase in the number of reinforcement layers up to an optimum of four layers. However, beyond this, a noticeable reduction in the bearing pressure was observed. Among reinforcement spacings, 0.3B delivered the highest bearing pressure, while larger spacings resulted in lower improvement. Increasing the relative density from 30% to 50% potentially improved the load-carrying capacity. With respect to the footing geometry, as the number of reinforcement layers increased from one to four, circular footings sustained a higher bearing capacity ratio, increasing from 2.89 for 1 layer to 12.25 for four layers, compared to square footings resting on the M-sand bed. The experimental results were compared with analytical predictions based on bearing-capacity approaches. The analytical results showed good agreement with experimental observations. Overall, the results demonstrate that M-sand can be effectively used as a backfill material in place of river sand, as it exhibits a comparable bearing resistance for a given settlement.