A simplified procedure for analyzing offshore wind turbines with suction and traditional piles under soil liquefaction

This article investigates the structural analysis and design of offshore wind turbine (OWT) support structures using both traditional and suction piles under soil liquefaction. A finite element model centered on a single suction pile was first generated to evaluate depth-dependent excess pore water pressure (EPWP) ratios near and away from the pile under liquefaction conditions. Findings reveal that suction piles exhibit substantial internal resistance to soil liquefaction, as shown by lower EPWP ratios inside the pile, which enhances soil stability and shear capacity. This resistance diminishes with distance from the pile, highlighting the stabilizing role of confined soil and water within the pile. Using depth-dependent EPWP ratios, the study establishes envelope curves for suction and traditional piles to adjust soil spring stiffness during liquefaction, aiding in structural analyses under diverse design load cases (DLCs) for OWT support structures. Results indicate that liquefaction-related conditions are not the primary factor influencing steel usage; rather, non-liquefaction DLCs govern design demands. Additionally, suction piles often require more steel than traditional piles due to installation pressures, though they remain competitive in deep waters. Settlement and tilting issues, particularly in liquefiable soils, underscore the need for careful design of suction piles on sandy seabeds.