Scour effects on the bearing capacity of monopile-wheel composite foundations under lateral and torsional loads

With the development of offshore wind power energy, the monopile-wheel composite foundation has attracted wide attentions from scholars as an innovative foundation for offshore wind turbines (OWTs). And in offshore engineering, the local scouring usually tends to weaken the bearing capacity by moving surrounding soil till even become a non-negligible reason for some engineering disasters. To explore this effect of local scour qualitatively and quantitatively, the scouring morphology of the monopile-friction wheel composite foundations under unidirectional flow are obtained by means of CFD. Then, a 3D finite element model is developed to estimate the bearing behaviors and deformation characteristics with the consideration of various scouring conditions. Both internal forces and failure envelopes under H-T combined loads are also obtained through numerical analysis. The results reveal that key scouring parameters significantly affect the bearing capacity and envelopes shrinkage of the composite foundation. In particular, the scouring depth has the greatest effect on lateral and torsional bearing behaviors of 15%-32% and 24%-58%, respectively, followed successively by the scouring angle and extent. And the loading point height has a noticeable impact on the lateral resistance of the composite foundation. The findings provide valuable insights into understanding the load bearing behaviors of composite foundations and their practical application in engineering.