The Lateral Behavior of Large-Diameter Monopiles for Offshore Wind Turbines Based on the p-y Curve and Solid FEM Methods

With the rapid increase in offshore wind turbines in China, monopiles with diameters exceeding 2 m are widely used. As these piles are subjected to lateral loads caused by wind, waves, and currents, the designs of the pile foundations supporting the offshore wind turbines are significantly influenced by their lateral behaviors. For this reason, field tests of the largest monopile on the sea and additional analysis based on the solid finite element method (FEM) and p-y curves are carried out to reveal the response of monopiles subjected to lateral loads and to figure out key technical issues related to the design process. The results revealed that the p-y curves proposed by the API code for clay showed a much "softer" response, which resulted in the conservative design of the piles. The solid FEM relied heavily on the choosing of the parameters used. At relatively small deflections, the solid FEM presented reasonable results as compared with the tests which were, however, supposed to overestimate the ultimate capacity of the piles. The results also indicated the importance of the influence of the pile-soil gap and the application of parameter analysis to achieve relatively conservative results, if the solid FEM is adopted in the design.