Effectiveness of sand compaction piles in improving loose cohesionless soil

This paper investigates the effectiveness of Sand Compaction Pile (SCP) in improving the density characteristics of cohesionless soil. The performance of SCP for different pile spacing, pile arrangement such as triangular and square, and coarseness of bed materials on the degree of soil improvement is studied in a better-controlled laboratory environment rather than more variable field environment. A SCP miniature device and a miniature dynamic cone penetrometer (DCP) were designed and fabricated in the laboratory. Sand beds containing loose cohesionless soil were prepared in a fabricated tank by sand raining from the pre-calibrated height. The SCPs were installed using the miniature device on the sand bed by displacing soil in the lateral direction in order to densify the bed prior to pouring sand in the displacement holes. The data of DCP in terms of penetration index and field density were measured at various depths to obtain correlation parameters between DCP and relative density of soil. This correlation was used to determine the relative density of improved soil beds due to the installation of SCPs. The improved soil condition was measured in terms of a decrease in penetration index or an increase in the relative density of bed materials. Some of the major findings include: the rate of increase of relative density due to installment of SCP is similar irrespective of the coarseness of bed materials; smaller pile spacing compared to an optimum spacing causes insignificant soil improvement; the triangular pattern shows better soil improvement compared to the square pattern for a given pile spacing.