Bounding-surface-based p-y model for laterally loaded piles in undrained clay

Abstract Pile foundations supporting long-span bridges, offshore platforms and offshore wind turbines often suffer from repeated lateral loads due to wind, waves and currents. To predict the degradation of the pile's lateral resistance and cumulative lateral deformation through cyclic loading, a theoretical cyclic p-y model is derived for a laterally loaded pile in undrained clay, formulated within the framework of the bounding-surface elastoplastic theory. Unlike the conventional p-y curves which models the degradation of the pile's lateral resistance based on the cycle number and amplitude, bounding surface contraction is employed in this study to model the softening of the soil resistance during laterally cyclic loading. To ensure practicability, the softening model parameter can be easily calibrated by the in-situ T-bar testing technique. A series of verifications with centrifuge tests having various pile-head conditions, pile-soil relative stiffness and load amplitudes are performed. The good agreement demonstrates its ability to predict the degradation of pile lateral resistance.