Experimental investigations on reliquefication resistance of saturated ground reinforced with ordinary and encased stone columns

Abstract

Recently, the observed devastation on structures due to soil reliquefaction highlights the need to assess the ground improvement techniques' performance under repeated shaking conditions. Ground improvement using stone column reinforcement was most popular due to its multimode benefits, such as installation-induced densification, drainage and shear reinforcement. Though the performance of the stone column improvement technique in liquefaction mitigation was well documented, the de-bonding of aggregates and column contamination due to the intrusion of surrounding soil grains during repeated shaking needs to be explored elaborately for assessing the performance of the technique. Similarly, encasing stone columns with geotextile material has recently been getting attention due to its confining and containment characteristics. Considering the above, the present experimental investigation attempted to use ordinary and geotextile encased stone columns for liquefaction and reliquefaction mitigation of saturated ground. The performance of the treatment technique was evaluated under repeated incremental shaking events. A saturated ground having 800 mm thickness with 40% relative density was used for the study. Four ordinary and encased stone columns having 120 mm diameter and 800 mm length, constituting an 8.0% area replacement ratio, were used for ground reinforcement. Both untreated and treated ground were subjected to repeated incremental acceleration loading, viz. 0.1g, 0.2g, 0.3g and 0.4g with a 5 Hz loading frequency. The generated pore water pressure ratio, soil settlement and foundation settlement for both treatment technique was monitored and compared with the untreated ground. The parameters influencing the performance of the ordinary and geotextile-encased stone column technique against liquefaction and reliquefaction hazards were evaluated and presented.