Evaluation of Load-Settlement Behaviour of Square Model Footings Resting on Geogrid Reinforced Granular Soils

Reinforced soil foundation is a soil foundation containing reinforcing elements or inclusions in the form of strips, grids or ties which are placed horizontally. The purpose of this research was to study the load settlement behavior of square footings placed on geogrid reinforced sandy soil foundation using model tests. While the geometric parameters are specific to certain specifications and conditions such as gradation, relative density of soil beneath the foundation etc., the type, aperture size, stiffness and thickness etc. of geogrid may have some effect on the critical parameters of the reinforced soil foundation. Therefore, two types of geogrid have been used in this study to investigate the load settlement behavior for model footings reinforced with uniaxial (UNX100) and biaxial (BIX100) polyester geogrids resting on poorly graded medium sand. Parameters of this study include the depth to the first reinforcement layer, spacing between reinforcement layers, plan area of the reinforcement and the grade of reinforcement. Load tests were conducted on model footings made of mild steel plates (100 mm * 100 mm size) in four phases to evaluate the effects of single and multiple layers of geosynthetic reinforcement placed below shallow spread footings and to quantify the difference in performance between the uniaxial and biaxial Geogrid reinforcement. Based on the current study, values for optimum embedment depth, optimum spacing between geogrid layers, and optimum plan area of reinforcement for both types of geogrid have been proposed. It was observed that inclusion of reinforcement increased the bearing capacity as well as decreased the settlement of the foundation. The presence of geogrid in the soil makes the relationship between the settlement and applied pressure of the reinforced soil almost linear. Biaxial geogrid performs better than uniaxial geogrid, though the uniaxial reinforcement also leads to significant improvement in performance of footings compared to unreinforced footings.