Numerical modeling of multi-directional lateral behaviour of pile foundations for offshore wind turbines in clay

This study investigates the lateral behavior of pile foundations for offshore wind turbines (OWT) under various loading paths in clay, including arc-shaped and cross-shaped trajectories, as well as the impact of occasional deviated loads on displacement accumulation. A finite element model that incorporates soil softening behaviour is established and validated against centrifuge tests conducted by the authors as well as reported in the literature. Following that a parametric study is conducted to explore the complex pile-soil interactions and examine how multi-directional loading influences the behavior of pile foundations. The results show that multi-directional loading significantly enhances pile displacement accumulation, with non-coaxial behavior observed as a mismatch between peak load and peak displacement. It is for the first time revealed that the most undesirable deviated loading angle ranges between 45° and 60°, and even one occasional event of deviated load can substantially impact cumulative displacement. The study further emphasizes the need to introduce a multi-directional loading factor to the design of OWT pile foundations.