Numerical investigation on bearing capacity of OWT foundation with large diameter monopile under Seismic load

Abstract

Dynamic characteristics of seabed soil under seismic load arevery important for the overall stability of the offshore wind turbine foundation. In this study, the horizontal bearing capacity and its corresponding soil deformation around the large-diameter monopile, where withstandsa transient high frequency seismic load, are simulated using a numerical method. During the numerical analysis in this paper, first a dynamic boundary surface model of saturated soil is derived instead of the empirical strength degradation method, and then a pile-soil contact model is considered instead of no-slip tie assumption. On the basis of the numerical results, an empirical degradation coefficient for the horizontal ultimate bearing capacity of monopile is proposed in this paper, which can well evaluate the effect of seismic load on the bearing capacity. Along the axis direction of the monopile, an intensive study about deformation law and failure mechanism of the seabed soil is analyzed by comparing somekey points at different crossing sections.Finally, some parameters which may affect the bearing capacity and the excesspore pressure are discussed. It can be found that the horizontal bearing capacity of the monopile can be obviously improved by increasing the buried depth than the diameter of monopile, and the seismic load has great influence on the soil deformation law around the monopile.