Static Response of Monopile to Lateral Load in Overconsolidated Dense Sand

Abstract

Large diameter, rigid monopile foundations have been extensively used in the fast-growing offshore wind energy industry over the last two decades. In view of the offshore environment, lateral response of the monopile usually governs its design. Even though several approaches have been recommended based on small-scale laboratory tests, there is no widely accepted method for the design of monopiles under lateral loading. Conversely, field testing on large-diameter prototype monopiles is normally impractical due to the high demand on the capacity of loading equipment. For these reasons a series of field lateral loading tests on reduced-scale monopiles were conducted at a dense sand test bed site. The model monopiles had similar aspect ratios of pile length to diameter to those used in the offshore wind farm projects, but were smaller in scale. Experimental p-y curves were derived using the measured monopile responses of the lateral load tests, and a distinctive failure model was presented for monopiles in the overconsolidated dense sand deposit. Comparison of lateral responses of monopile between the measured and predicted by two current p-y models showed the shear force at the pile tip plays an important role and should be accounted for in the design of laterally loaded rigid monopiles. Finally, a refined p-y model for laterally loaded rigid monopiles in overconsolidated dense sand was recommended and calibrated.