Performance of Clay Bed with Natural and Lightweight Aggregate Stone Columns

Abstract

Booming infrastructure activities demand suitable subsoil conditions to accomplish design requirements in terms of strength and serviceability. Soft soils encountered during such activities may pose problems such as very low strength, poor hydraulic conductivity, shrinkage and swelling with seasonal moisture variations etc. Utilization of sites with soft soils required the invention of various ground modification techniques. Stone columns is one of such techniques used in soft soils to improve its load bearing capacity, dissipate excess pore water pressure rapidly and reduce the total settlement effectively and economically. Stone columns require use of natural aggregates to be transported from a distant place to the construction site that causes an increase in construction cost, carbon footprint and diminish natural resources. This paper presents laboratory investigations of load test results on virgin clay bed and clay bed with stone columns. Two different conditions of stone columns viz. (1) un-encased stone columns with natural and lightweight aggregates (2) encased stone columns with natural and lightweight aggregates. Clay beds were prepared using slurry consolidation method by mixing dry soil with water content equal to 1.5 times liquid limit of the soil. Displacement controlled load tests were performed on clay beds with and without stone columns. Loads against applied displacements were continuously monitored for all the tests conducted. Clay bed with stone columns demonstrated higher load carrying capacity as compared to virgin clay beds. Un-encased stone columns indicated increase in bearing capacity by 31.7% for natural aggregates and 19.5% for light weight aggregates as compared to virgin clay bed. Further, provision of encasement to the stone columns increased load carrying capacity to 36.6% for natural aggregate stone columns and 31.7% for light weight aggregate stone columns as compared to virgin clay bed.