Interaction between large-diameter offshore wind turbine monopiles and adjacent spudcan penetration and extraction in clay

Large-diameter monopiles are used for offshore wind turbines, while adjacent jack-up spudcan operations may induce soil deformation and compromise serviceability. Existing spudcan–pile interaction studies have focused on pile response during penetration, with limited attention to monopile rotation during extraction. This study investigates monopile rotation in normally consolidated clay throughout a spudcan penetration–extraction cycle using three-dimensional large-deformation finite-element analyses based on the Coupled Eulerian–Lagrangian (CEL) approach. The model is validated against centrifuge data on spudcan resistance, adjacent-pile bending moments, and soil deformation mechanisms. Results show that monopile response is dominated by rotation rather than translation, and its direction evolves with the migration and reversal of spudcan-induced soil flow relative to the pile. Extraction is generally more adverse than penetration, with peak rotation reaching approximately three times the penetration peak in the reference case. Spudcan–monopile clearance is the primary controlling factor, while soil stiffness, undrained shear-strength gradient, and monopile embedment length influence rotation. Prediction equations are developed for the penetration peak, overall maximum, and residual rotations within the investigated parameter ranges. These findings extend spudcan–monopile interaction research by addressing extraction-induced monopile rotation and linking its evolution to soil deformation mechanisms, providing a basis for assessing risks to adjacent offshore wind monopiles.