Investigation on offshore wind turbine with an innovative hybrid monopile foundation: An experimental based study

The support structure for offshore wind turbines (OWTs) plays significant roles in maintaining the structural stability and reducing the initial cost. An innovative hybrid monopile foundation for OWTs is proposed. The concept has a wider adaptability by using established knowledge to solve for new problems. A series of centrifuge tests is performed to investigate the behavior of this hybrid foundation system in extreme and service conditions. OWTs with the original monopile foundation as well as the wheel-only foundations are tested for comparisons, and two clay profiles are considered. The test results show that the hybrid monopile foundation provides larger ultimate bearing capacities compared to the traditional foundations. Two analytical methods are proposed to estimate the ultimate bearing capacity of this innovative design, and the results are calibrated by the centrifuge tests. In service conditions, the hybrid monopile foundation shows stronger cyclic resistances. Influence factors of the cyclic responses are summarized. An analytical solution is put forward to estimate the accumulated lateral displacement of the hybrid monopile foundation. A degradation factor is suggested based on the results of the centrifuge tests. The study aims to enrich the understanding of the innovative foundation concept and to provide design references for practical applications.