Large-Scale Direct Shear Tests on Soft Clay Treated with Reinforced Lime Columns

Although the use of lime columns to improve the shear strength of soft clay has been extensively studied, the potential benefits of reinforcing these columns with reinforcement bars have not been sufficiently emphasized. This paper attempts to fill this research gap through a series of large-scale direct shear box tests on soft clay improved with a single reinforced lime column. The main objectives of the experimental study were to investigate the following controlling parameters: reinforcement and embedment ratios of steel and the curing period of lime. In order to further evaluate the efficacy of the inclusion of reinforcement bars in the lime columns, the results were compared with those found in the literature for unreinforced lime columns. The results revealed that every 0.1% increase in the reinforcement ratio caused an average increase of 2 kPa (13.3% of the shear strength of the virgin soft clay). The steel could prevent the sudden brittle failure observed in unreinforced lime columns by providing ductility and retarding the shear failure. When compared with untreated soft clay, the inclusion of steel in the lime column could increase the shear displacement at failure by 6–32% depending on the reinforcement ratio.