Centrifuge modeling of pile foundation under multi-directional earthquake loading

Ground motions in real earthquakes are three-directional in nature. However, seismic response of pile foundation has been simulated only under one dimensional shaking at centrifuge in the past, due to the limitation of test facilities. Recently, a series of dynamic model tests have been performed by use of the biaxial shaking table at HKUST (The Hong Kong University of Science & Technology) centrifuge, with the aim of investigating the effect of multi-directional shaking on soil-pile interaction. This paper presents and compares responses of single pile and pile group embedded in level liquefiable sand deposits, when subjected to 1D and 2D earthquake loadings. Preliminary analyses of the results suggest that the responses of pile foundation along two mutual perpendicular horizontal directions may be considered independently under small vibrations, but orthogonal loading effect appears and could not be ignored as the relative displacement between pile and soil increases. The results also imply that rigorous and comprehensive approaches are desirable in order to reproduce or predict response of soil-pile-superstructure system under multi-directional seismic loading.