Abstract: Large-diameter single pile foundation is a typical foundation type for offshore wind turbines. Model tests of large-diameter single pile are conducted using a simple mechanical load rig designed in-house in sand. The cumulative deformation response of a single pile under long-term lateral cyclic loading is discussed. The test results indicate that the cumulative displacement of the pile head presents two phase characteristics with number of cycles, and the short-term effect for lateral cyclic loading is greater than the long-term effect. Sand density and cyclic loading paths greatly influence the displacement characteristics of the pile head. The lateral secant stiffness of the pile head increases with cycling under different initial conditions. The change of horizontal static bearing capacity of single pile after cyclic loading in sands of different densities is not completely consistent with hard-soft mechanism for loose-dense sand subjected to shear. The prediction model parameters for lateral cyclic cumulative displacement of single pile are obtained by use of the empirical formula method. Comparison between the calculation results and the test results show that this model can effectively predict the cumulative displacement of single pile under different cyclic paths.

Key words: single pile, sand, lateral cyclic loading, cumulative displacement, prediction model