Centrifuge study of p-y curves for vertical-horizontal static loading of piles in sand

Pile foundations for offshore structures are subjected to vertical-horizontal load combinations. The current design method separately analyses horizontal and vertical responses of piles without considerations of the combined effect of the loads on soil-pile interaction. However, there is experimental and numerical evidence that lateral behaviour of a pile-soil system can be affected by both axial compression and tension load on the pile. In this study, two singlepile and two tripod-pile centrifuge model tests under different loading conditions were analysed to investigate the influence of combined loads on the lateral response of the soil-pile system. The displacement and the bending moment were measured and analysed to highlight the behaviour of the pile-soil system under different loading conditions. The p-y (resistance-deflection) curves for the different tests were calculated and compared to reveal the influence of the axial load component on the lateral behaviour of soil-pile systems. It is concluded that compared with pure lateral loading, the p-y curves of piles under compression are steeper due to the soil densification effect, while the opposite is observed under tension load - that is, the p-y curves are gentler.