Study on p-y Curves of Large-diameter Steel Pipe Piles for Offshore Wind Farm in Sand Based on In-situ Tests

A series of in-situ tests on lateral monotonic loading of two offshore large-diameter steel pipe piles in sand are performed, and the lateral load versus displacement relationship, bending moment and deflection of pile shaft and lateral soil pressures are measured. The results show that the maximum bending moment approximately is 1D m (one time diameter of pile) below the ground level, the zero pile shaft deflection point is approximately 7 m below the ground level. Based upon the measured results, the initial modulus and the ultimate resistance of p-y curves in silty sand are studied, and a modified hyperbolic model considering the influence of pile diameter and embedded depth is employed to calculate the sand p-y curves, the comparisons of p-y curves at the depth 2D (two times the diameter of pile) between API code and other refinement models are presented. The results show that the initial modulus is overestimated and the ultimate resistance is underestimated by the API code, which lead to small lateral displacement estimation when small pile shaft deflection occurs, and the lateral displacement estimation is conservative when large pile shaft deflection occurs. Furthermore, the initial modulus and the ultimate resistance are underestimated by the hyperbolic model, the modified hyperbolic model offers a better prediction for silty sand deposits.