The behavior of geogrid-reinforced sand soil supporting shallow footing under earthquake

Abstract Earthquakes are detrimental phenomena that can result in significant loss of lives and infrastructures. During earthquakes, shallow foundations can suffer considerable settlement, tilting, and sliding resulting in foundation failure. One of the promoting techniques that can enhance soil performance is soil reinforcement using geogrid. Until recently, there are very limited studies that concern with the response of the square foundation when founded on geogrid-reinforced soil. This study aims to examine the influence of square footing founded on sand soil with and without geogrid reinforcement under the 2017 Halabjah earthquake using a shaking table system. The soil was prepared with relative density of 30% with and without reinforcement. The sand was reinforced with one, two and three layers of geogrid type InterAx NX750 supplied by Tensar Company. The first layer of geogrid was placed at depth of 0.3B, the distance between the geogrid layers was 0.3B, and the length of the geogrid is 4B (B: footing width). The shaking table used in the study was fabricated locally. The settlement and horizontal displacement, tilting, acceleration and pore pressure were measured using a rope displacement sensor, tilt sensor, accelerometers and pore pressure transducers respectively. The results showed that the use of geogrid reinforcement can enhance the soil behavior by decrease the foundation settlement and displacement, and minimize the tilting of the footing. The highest decrease in the settlement and titling of the footing was given by the soil reinforced with three layers of geogrid. The results also showed that reinforcement decreases the amplification of the acceleration. In addition to the decrease in the pore pressure developed in the saturated sand soil and in consequence decreases the liquefaction ratio (Ru). Nevertheless, the influence of the geogrid reinforcement on the liquefaction ratio and acceleration are lower than that of settlement, and tilting.