Numerical Study on Behaviour of Encased Stone Columns with Partial Content of Shredded Tyre Chips in Soft Clay Bed

Abstract

The utility of construction of stone columns in soft soil like clay, marine soil in coastal regions as a ground improvement technique is widely acknowledged. This study presents a numerical analysis of behaviour of ordinary and encased columns, made of various mix proportions of shredded tyre chips and stone aggregates, through Finite Element modelling (with Plaxis 3D software). It is observed that encased columns exhibited remarkable decrease in bulging with respect to ordinary columns. This was true even for columns composed of high proportion of tyre chips (50–100% by volume) owing to generation of higher hoop strain in such columns. The development of hoop strain increased the tensile strength of encasement and hence the column stiffness. The study illustrates the variation of maximum lateral deformation and the corresponding depth with the amount of tyre chips in the mix proportion forming the column. A decrease in bulging along with bulging at greater depths was observed in encased columns, the bulging was negligible for columns wherein the tyre content varied between 0 and 30% by volume. The settlement reduced remarkably with the construction of encased columns irrespective of the mix proportions composing the columns. The study concludes that partial replacement (30–70% by volume) of stone aggregates with shredded tyre chips in encased columns in soft soil is feasible with encasement of significant stiffness.