New p-y curve model considering vertical loading for piles of offshore wind turbine in sand

Pile foundations in offshore engineering are usually subjected to vertical-horizontal load combinations. Previous researches have discovered that the lateral behaviour of soil-pile system could be influenced by axial load due to P-Delta effect and the change of soil stiffness, but the mechanism and influencing factors are still unclear. The current p-y curve method for laterally loaded piles is independent on vertical loads, which is not often applicable for offshore piles. In this study, numerical analyses with the Hypoplastic constitutive model were employed to simulate the vertical-horizontal combined loading pile in sand. The results of soil-pile system under different vertical-horizontal load combinations were compared to confirm and further investigate the change of soil stiffness due to vertical loads. The mechanism and the influencing factor of the change of soil stiffness were clarified by analysing the change of soil stiffness under pure vertical loading conditions. Based on the above studies, a new p-y curve model for vertical-horizontal combined loading piles in sand was established. The parameter determination method was proposed. The effectiveness of the new p-y model and the parameters were verified by comparing the back-calculated results with those from numerical simulations.