BEHAVIOUR OF STONE COLUMN IN LAYERED SOILS USING GEOTEXTILE REINFORCEMENT

Due to ever increasing infrastructure development, space constraints particularly in metropolitan cities we are forced to construct the structures on weak soils like soft clays, which cover a vast area all along the coast. To improve this soft soil of very low shear strength and high compressibility, different techniques for ground alteration and improvement are available around the world. They include dewatering, vibro compaction, preloading of soil with and without vertical drains, vacuum consolidation, grouting, deep mixing, densification, soil reinforcement etc. (1). Amongst these techniques for improving in situ ground conditions, strengthening the ground with stone columns or granular piles is one of the most popular and cost effective technique (2). Stone columns increase the bearing capacity of the foundation, slopes stability and reduces total and differential settlements, accelerates the consolidation time and decreases the liquefaction potential. The stone column and its surrounding soil acts as a composite material and the stiffness of this composite ground is much higher than the soft soil (3). Applications of stone columns include, supporting the earthen embankments, liquid storage tanks, raft foundations and other low rise structures (4). Encased stone column have gained popularity as compared to the conventional stone column. The concept of encasing the stone columns was first intended by Van Impe in 1985. The advantage of encasement is it reduces the settlement of composite foundation and increases the load carrying capacity