Numerical investigation of resistance components distribution for lateral loaded offshore wind turbine monopile

Abstract

With the increasing capacity of offshore wind turbines, the diameter of wind power monopiles has been continuously growing, leading to a significant decrease in the length-to-diameter ratio (L/D). Existing methods primarily focus on correcting the p-y curve due to increased pile diameter but fail to adequately consider the impact of changes in resistance components distribution resulting from a decreased L/D. This study aims to analyse the pile-soil interaction of large-diameter horizontally loaded monopiles by examining the distributed resistance components. Through finite element analysis and verification via engineering pile testing, the paper explores the resistance composition, deformation characteristics, and changes in resistance components of large-diameter monopiles. The findings reveal that the pile-soil horizontal resistance primarily governs the lateral bearing capacity of large-diameter monopiles for small range of length-to-diameter ratios (4 ∼ 10). It is found that the deformation mode of monopiles is controlled by the pile-soil relative stiffness. A p-y resistance component curve for large-diameter horizontally loaded monopiles under various interlayer states of sand and clay was proposed as a function of pile-soil relative stiffness. For engineering practice, a simple but useful method for evaluating and correcting the lateral bearing capacity of monopiles was demonstrated based on the proposed resistance component curve.