Lateral Bearing Capacity of a Hybrid Monopile: Combined Effects of Wing Configuration and Local Scour

Abstract

Pile foundations for offshore wind turbines are subjected to large lateral loads. By mounting wings on the perimeter of regular monopiles, winged monopiles have shown better performance in resisting deformation under horizontal loading. However, the hazardous effect of local scour on the lateral bearing capacity of winged monopiles installed in the sandy seabed has not been systematically evaluated. In this study, a modified Mohr–Coulomb model considering the pre-peak hardening and post-peak softening behavior of dense sand is adopted to simulate laterally loaded winged monopiles in the locally scoured sandy seabed, using three-dimensional finite element analyses. The effect of local scour depth on the lateral capacity of winged monopiles is examined and explained by soil failure mechanisms. The enhancement of lateral capacity with wings attached to the monopile is demonstrated to be more effective than extending pile embedment length. The effects of the relative density of sand and the wing load orientation are also discussed. Finally, the wing efficiency is evaluated to determine the optimal configuration of winged monopiles.

Holding capacity of a novel hybrid helical-skirted foundation of offshore wind turbines

“…Various hybrid foundations have been proposed to accommodate the increasing turbine size and the associated substantial loads exerted on the superstructure. Some examples are the combined monopile and a circular footing [4,5], the winged-monopile [6,7], the piled concrete foundation [1], the shallow skirted footing with a deeper caisson [8], the monopile coupled with a skirted footing [9], the gravelfilled friction wheel on the mudline with a monopile [10].…”