Lateral bearing behaviors of wheel-reinforced monopile foundations for offshore wind turbines in sand

This study examines a wheel-based reinforcement strategy for extending the service life of monopile-supported offshore wind turbines (OWTs) in sand. With a typical service life of 20–25 years, many OWTs are approaching the decommissioning stage, and service life extension and repowering are viable alternatives to full removal. In the paper, the lateral reloading behavior of wheel-reinforced monopiles is investigated through 1 g model tests and finite element analyses. The reinforcement mechanisms of existing monopiles with wheels are analyzed firstly, followed by a systematic investigation of key influencing parameters, including pre-loading conditions, wheel diameters, and horizontal loading point heights. Finally, an empirical formula for the reloading bearing response is proposed. Results demonstrate that reinforcing monopiles with wheels is effective in enhancing the reloading performance. Increasing wheel diameter improves lateral bearing capacity by up to 47% when the diameter is less than half the embedment depth, whereas increasing the loading point height reduces capacity by more than 50%. Moreover, pre-horizontal loading exerts a stronger adverse effect on reloading performance compared to pre-vertical loading. These findings provide valuable insights for extending service life of monopile-supported OWTs.