Effects of local scouring on the bearing capacity of monopile-wheel composite foundations in sandy deposit

Abstract

The monopile-friction wheel composite foundation is an innovative offshore wind turbines (OWTs) foundation type for its good bearing properties and anti-erosion advantages. The local scouring is a non-negligible challenge by moving surrounding soils away till even some engineering disasters. To explore this kind of unfavorable effects, we model the response of scouring to the bearing capacity of the composite foundation by means of laboratory flume tests. Furthermore, the influence of different loading sequences (i.e., T→H or H→T) is considered, and the failure envelopes are also obtained. On this basis, a 3D finite element model is established to investigate the impact of key scouring parameters and different loading point heights on the bearing capacity. The conclusions are as follows: local scouring can significantly reduce the bearing capacity; the scouring depth has the most significant effect, followed successively by the scouring angle and extent; compared with pure horizontal foundations, the ultimate torsional bearing capacity of the foundations under the combined T→H loading sequence decreases by about 1.95%–11.1%, while the horizontal bearing capacity under the combined H→T loading sequence decreases by about 0.82%–1% compared with pure torsional foundations; the loading point height has noticeable effects on the lateral resistance for the composite foundation.