Behavior of Geosynthetic Encased Stone Column

Abstract

The satisfactory advantages of the stone column have enhanced the popularity as a ground improvement technique, particularly for soft soil. This technique is best suited for structures that can tolerate some amount of settlement. The effectiveness of the granular column becomes limited because of low confinement of the surrounding soil. Here, the significant improvement of load-carrying capacity due to partial encapsulation of normal stone column has been investigated. In this study, the effects of vertical circumferential encasement have been analyzed using finite element package Plaxis. To simulate with the field condition, stone column unit cell model of diameter 1 m has been constructed in the clay layer of 15 m thick. The load-carrying capacity of a floating stone column was found to be increased significantly up to a length of four times the diameter and beyond this length; no remarkable increment of bearing capacity has been observed due to lateral bulging. If bulging is restrained by circumferential encasement, the load-carrying capacity continues to increase with the length. From the study, it was found that the full encasement is not economical and the encasement at the top 25–30% of the total length is sufficient to mobilize full performance. Bearing pressure and stress concentration in the column material increases with the stiffness of the circumferential encasement. The shape of the hoop tension distribution diagram in geogrid is similar to the bulging pattern.