Ground Improvement using Encased Stone Columns

Abstract

The problem of soft soils along coastal regions, weak subsoil conditions and poor fill soils renders construction difficulties for geotechnical engineers. To conquer these obstacles, a variety of soil improvement strategies are available. One of the most common methods for supporting construction in such site conditions is the use of granular stone columns. However, due to the low lateral confinement offered by the surrounding weak soil, stone columns undergo failure due to squeezing of stone column material into the adjacent soil. This diminishes the structural integrity of the employed technique and renders a compromised load capacity and settlement behaviour. Thus, encasement of granular columns has been utilized for rectifying the aforementioned concern. newline The present study investigates a typical soil condition readily encountered by the site and Geotechnical engineers consisting of weak cohesionless soil over a comparatively stiffer underlying soil layer. Such soil profiles have been reported in the literature and are a common condition found along the Indian coastal region, parts of the mainland and abroad. The use of stone columns in soft cohesive soils for improving load capacity is comprehensively investigated and reported in the available literature. However, amongst the very few studies of reinforcing poor cohesionless soil using rammed stone columns, the outcomes from the present study will contribute significantly in precisely deciphering and validating the load capacity and failure mode depicted by conventional floating stone columns when installed in cohesionless soil condition. The present study further adds to the existing literature by investigation of effect of vertical and horizontal encasing/reinforcing the stone columns for mitigation of bulging failure suffered by conventional floating stone columns under compressive load in cohesionless medium. newline In the present study, model testing of a single unreinforced stone column (diameter 40 mm and length 300 mm) treated as a representation of a con