Capacity of monopile-bucket composite foundations in sand-overlaying-clay deposits under lateral loading

The monopile-bucket composite foundation is an innovative offshore wind turbines (OWTs) foundation type for its good bearing properties. This paper establishes the 3D finite element models to explore the lateral bearing behaviors for the composite foundations in sand-overlaying-clay deposits. After model verification, the failure mechanisms of the monopile foundations, single suction bucket and monopile-bucket composite foundations are systematacially analyzed. In addition, a detailed parametric study is undertaken to quantify the effects of potential parameters on the lateral bearing behaviors of composite foundation. Finally, the load sharing ratio between the monopile and suction bucket in composite foundation under lateral loading is investigated. It is found that the composite foundation is superior to that of single pile. Increasing the bucket diameter, bucket length, and overlaying sand layer thickness, the bearing capacity of composite foundation can be enhanced. Among them, the variation of bucket diameter has the most significant effect, while raising the loading point height will weaken the lateral resistance. When the dimensionless pre-vertical load increases from 0 to 0.7, the foundation bearing capacity is improved, and more than 0.7 leads to weakening.