Winkler model based p-y curve method has been widely used in the design of laterally loaded pile. This semi-empirical method was originally proposed for the offshore oil/gas platform and developed from field lateral loading test results mainly on flexible piles with diameters not greater than 1.2 m and ratios of pile embedded length to outer diameter larger than 20. In the past decade

the boom in the wind energy industry

especially for offshore

has increased the dimensions of piles out of the range for derivation of current p-y models. To date

it is generally agreed that

for the design of a laterally loaded pile with a large diameter

such as diameter 6 m

the reliability of current p-y models is not clear and should be further investigated. According to the test results of two laterally loaded piles

a detailed case study was conducted to investigate the p-y model recommended by the API code and other researchers’ refinement. The results show that the negligible error is shown in bending moment predicted by different p-y models. The pile head deformation is mainly dependent on the initial stiffness of subgrade reaction and the expressions of p-y models. Not only the internal friction angle and relative density of sands

but also the geological history of ground should be considered for determining constant of subgrade reaction stiffness. Finally

future study is highlighted.