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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. [ABSTRACT FROM AUTHOR]

This paper presents a program of centrifuge model tests (100g) on the monotonic and cyclic lateral loading behavior of monopiles. The diameter and burial depth of the model pile were 59 and 550 mm, respectively, and the soil used was Fujian sand with a relative density of 70%. During monotonic loading, a linear relation between the lateral soil resistance and the pile deflection was observed, with the slope increasing linearly with soil depth. For the sand sample used in this study, the loading rate had a surprisingly weakening effect on the lateral pile–soil interaction. This was confirmed by the development of positive excess pore pressure (EPP) and the contraction behavior observed in triaxial tests. During cyclic loading, the EPP oscillated at a constant amplitude, without any accumulation with the number of cycles, and the relation of the oscillation amplitude to pile deflection velocity was derived. Implications for practice in the field when assessing the lateral pile–soil interaction of monopiles considering EPP development characteristics were discussed. [ABSTRACT FROM AUTHOR]