Ultimate Lateral Capacity of Large Diameter Monopiles Embedded in Sand

Large diameter monopiles are considered to be sustainable foundations for supporting large offshore wind turbines in shallow to medium water depths. In view of the offshore environment, lateral response of the monopile usually governs its design. Even though several approaches based on small-scale laboratory tests have been recommended, there is no widely accepted method to calculate the ultimate lateral capacity (Pu) of monopiles. Conversely, field testing on large diameter monopiles is normally impractical due to the high demand on the capacity of loading equipment. The current design procedure for the design of monopiles is the p−y curve method adopted in the America Petroleum Institute (API). In principle, this method is based on limited field tests which are conducted on small diameter piles (i.e., D is less than 0.65 m). Therefore, it cannot be used for monopiles with large diameters accurately. Thus, there is a big need to establish a reliable expression that can calculate the ultimate lateral capacity of large diameter monopiles. This paper presents an attempt to establish an analytical expression to calculate the ultimate lateral capacity of large diameter monopiles embedded in medium to dense sand. The response surface methodology is used in conjunction with the finite element method to establish this analytical expression. At the end of this paper, the accuracy of the established expression was checked, and it was found to present accurate results.