Evaluating the p - Y Curve Method of Analysis for Large-Diameter Monopiles Using Centrifuge Modelling

Centrifuge model tests were performed to evaluate the structural response of offshore wind turbine monopile foundations in sand subjected to lateral loading. Model monopile foundation tests were performed at 100 gravities (100g) of a prototype pile 5 m in diameter (D). Three embedment depths (L) of 20 m, 30 m and 40 m (L/D = 4, 6 and 8) were evaluated under an increasing monotonic lateral load. Evolution of pile head deflection, lateral force and consequential pile bending moments were monitored. Comparison of the observed and predicted deflected shape and pile bending moments indicates that the design codes p - y methods of analysis may underestimate the two parameters by up to 30 percent. Additionally, upon unloading, the monopile experiences a degree of 'locked-in' moment, which suggests an increase in horizontal restraint due to sand particle restructuring in the principle axis of bending during the initial load application.