STUDY ON DESIGN METHODS OF HORIZONTALLY LOADED LARGE-DIAMETER MONOPILE IN CLAY

This paper compares four design methods of horizontal loaded monopile under monotonic loading in clay. They include API method based on p-y spring model,Zhang et al.(2017b) method based on p-y spring model,Wang et al.(2020) method based on double-spring model,and Fu et al.(2020) method based on triple-spring model. Two typical length-diameter ratios of large diameter monopile(L/D=5 and 10) are considered. The four methods are analyzed by comparing with the results of 3D finite element analysis. The influence of different parameters on the prediction results is discussed. The results show that:(1)For the deflection and rotation of a large diameter monopile,the current API method is the most conservative,while Wang et al.(2020) method provides the lowest predictive results. (2)Fu et al.(2020) method not only incorporates the shear force at pile tip and the distributed moment along the pile induced by frictional resistance,but also is capable of capturing the effects of initial shear modulus and soil ductility on horizontal response,which makes it superior to the other three methods; (3)In the design of monopile using Fu et al.(2020) method,the larger the interface roughness coefficient α is,the greater the pile deflection and rotation are. The influence is more significant with larger length-diameter ratios. The effect of coefficient ξ_p2 related to the distributed moment along the pile is relatively limited,which is negligible for L/D≥10.