Experimental Study on the Improvement of Bearing Capacity of Soft Clay by Using Reinforced Sand Cushion Resting on Encased Stone Columns

Soft clay deposits present challenges such as high settlement and low bearing capacity in construction projects. Various techniques, including stone columns and encased stone columns, have been developed to reduce settlement and enhance bearing capacity in soft clay soils having cohesion (Cu) less than 25 KPa. This research investigates the use of ordinary stone columns and encased stone columns through experimental modeling. Additionally, the study aims to enhance the bearing capacity of soft clay soil by using reinforced sand cushion resting on encased stone columns. A series of tests were conducted with various parameters such as geosynthetic materials, column diameter, and spacing. The results were analyzed in terms of stress-settlement curves and improvement ratios. The findings demonstrate that the diameter of stone columns significantly influences in bearing capacity, with optimum economic improvement ratio achieved at 50% of the footing diameter. The optimal spacing between stone columns is twice their diameter for the best performance and economic efficiency. The best economic thickness of the sand cushion over encased stone columns is 0.2 times the footing width. The optimal diameter for the reinforced sand cushion is approximately two and a half times the footing width; any further increase results in negligible improvement. The bearing capacity of reinforced sand cushions is more than double that of unreinforced sand cushions.