Scour effects on the bearing capacity of multi-bucket jacket foundation for offshore wind turbines

Abstract

The Multi-Bucket Jacket Foundation (MBJF) is presently being installed in Chinese wind farms with increasing numbers. Compared to monopiles, MBJF is a shallow foundation and the effect of scouring on the bearing capacity is more significant. This research proposes a universal three-dimensional model of the MBJF with local scour to efficiently estimate the effect of scouring on the MBJF bearing capacity. Firstly, using the proposed model, the ultimate bearing capacity is calculated under a single load, and the discounting effect of different scour ranges and scour depths on the ultimate bearing capacity is evaluated. Furthermore, the fixed load-displacement approach is used to calculate the failure envelope of the foundation under composite loading mode, and the influence of different scour patterns on the failure envelope is compared. The findings reveal that when the scour extent and depth increase, the foundation's bearing capacity decreases non-linearly, and the foundation bearing envelope line gradually shrinks. Under the condition that the ultimate vertical load is not exceeded, a rise in vertical load can enhance the ultimate load capacity after scouring to a certain extent. Finally, the calculated envelopes are integrated with engineering applications to quantify the safety redundancy of the MBJF bearing capacity for different seabed morphologies. The method and results can provide methodological support for the accurate prediction and efficient assessment of the MBJF's post-scour bearing capacity.