The present study investigates the improvement in the bearing capacity of silty clay soil with thin sand layer on top and placing geogrids at different depths. Model tests were performed for a rectangular footing resting on top of the soil to establish the load versus settlement curves of unreinforced and reinforced soil system. The test results focus on the improvement in bearing capacity of silty clay and sand on unreinforced and reinforced soil system in non-dimensional form, that is, BCR. The results show that bearing capacity increases significantly with the increased number of geogrid layers. The bearing capacity for the soil increases with an average of 16.67% using one geogrid layer at interface of soils with equal to 0.667 and the bearing capacity increases with an average of 33.33% while using one geogrid in middle of sand layer with equal to 0.33. The improvement in bearing capacity for sand underlain silty clay maintaining and equal to 0.33; for two, three and four number geogrid layer were 44.44%, 61.11%, 72.22%, respectively. The finding of this research work may be useful to improve the bearing capacity of soil for shallow foundation and pavement design for similar type of soil available elsewhere. 1. Introduction The use of geosynthetic materials to improve the bearing capacity and settlement performance of shallow foundation has gained attention in the field of geotechnical engineering. For the last three decades, several studies have been conducted based on the laboratory model and field tests, related to the beneficial effects of the geosynthetic materials, on the load bearing capacity of soils in the road pavements, shallow foundations, and slope stabilizations. The first systematic study to improve the bearing capacity of strip footing by using metallic strip was by Binquet and Lee [1, 2]. After Binquet and Lee’s work, several studies have been conducted on the improvement of load bearing capacity of shallow foundations supported by sand reinforced with various reinforcing materials such as geogrids [3–9], geotextile [10–12], fibers [13, 14], metal strips [15, 16], and geocell [17, 18]. Several researches have demonstrated that the ultimate bearing capacity and the settlement characteristics of the foundation can be improved by the inclusion of reinforcements in the ground. The findings from several laboratory model tests and a limited number of field tests have been reported in the literature [19–25] which relates the ultimate bearing capacity of shallow foundations supported by sand reinforced with multiple layers of geogrid.
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