Comprehensive Experimental Investigation of Improved Clay Ground by Sand Compaction Pile Varying from Low to High Area Replacement Ratios

Abstract

A sand compaction pile (SCP) with a high area replacement ratio (>50%) has been recently employed to improve the soft clay ground in offshore projects, but its performance is still not completely known. Therefore, to provide a comprehensive understanding of the SCP method, a series of laboratory model tests were performed on the SCP-improved clay ground using high (70% and 100%) and the low-to-medium (0%, 14%, and 38%) area replacement ratios. The internal stress and strain responses of SCP-improved ground with a high area replacement ratio were different from those with a low-to-medium ratio. Typically, under high ratios, the loaded SCPs bulged, resulting in the bending of the adjacent SCPs, while under low-to-medium ratios, the SCPs deformed individually. Essentially, the additional lateral confinement is provided by the adjacent SCPs under the high replacement ratio. An improved model to predict the bearing capacity of the SCP-improved ground was proposed by incorporating a coefficient of lateral pile interaction that reflects the failure mechanism. The prediction using the proposed model showed good agreement with the observations in the west artificial island of the Hong Kong–Zhuhai–Macao Bridge project. This study provides a universal mathematical model to predict the bearing capacity of the clay ground improved by SCP varying from low to high area replacement ratios, leading to a comprehensive understanding of the performance of this modern technique.