Offshore wind power has a huge potential growth as a kind of renewable energy. Today one of the most common concepts for wind turbine foundations is the very large-diameter monopile. The conventional method for assessment of steel-pipe pile lateral performance is the application of p-y curves recommended in API RP 2GEO. However, the applicability of the API method for large-diameter monopile needs to be further studied. 3D finite element analyses are performed for the behaviour of the laterally loaded large-diameter monopiles. A work hardening soil constitutive model for saturated clay is used in these analyses, which has been calibrated with the results of stress-strain soil behaviour. Based on this model, parametric studies for different slenderness ratios have been developed for the pile lateral bearing capacity and p-y curves. The deformation features of piles are gradually transformed from flexible piles to rigid piles with the decrease of the slenderness ratio. Through comparing the numerical results with analytical results obtained by API method, the scope of application of existing p-y curves method is ensured.
Offshore wind energy produced by wind turbines has become a promising source of renewable energy and will grow enormously in the coming years. Although the costs of installing a wind turbine in offshore wind farms are 30% – 50% higher than onshore wind farms, they encounter higher average wind speeds and save landing resource. Meanwhile, the development of offshore wind energy has encountered a series of challenges, one is determining the option of a foundation type and the design principle of the foundation. Up to now, five typical types of the foundations have been proposed: gravity foundations, monopile foundations, jacket structures, suction caissons and floating systems (Lombardi et al., 2013). The advantages of offshore steel piles are the simplicity of manufactures and installations as well as the widely successful experience in offshore gas and petroleum engineering field. Thus, monopiles are still the most common support structure of offshore wind turbines (>75%), typically used in water depths ranging from 15m and 35 m (Doherty and Gavin, 2011; Aissa et al., 2018; Damgaard et al., 2014).