The scour hole around a pile will reduce the capacity of a laterally loaded pile. The strain wedge model is capable to derive a p–y curve for the analysis of a lateral loaded pile on a nonlinear Winkler foundation. To improve and extend the ability of the strain wedge method, a modified strain wedge (MSW) method is developed, in which a nonlinear lateral deflection of the pile is assumed to describe the varied soil strain distribution in the passive wedge. And then by treating the soil weight involved in the strain wedge as a vertical load at the bottom of the scour hole, an equivalent wedge depth is obtained to consider the effect of scour hole dimensions on the response of laterally loaded piles in sand. The validity of the MSW model is proved by comparisons with a centrifuge test without scour. And its applicability in the problem of a pile with scour is performed by a comparison with a model test and a FE analysis. The analysis shows the pile displacement at the pile head with scour can be obtained by multiplying the corresponding deflection without scour with an amplification factor related to scour depth at large load level.

The wind turbine has become an efficient way for clean energy. For offshore wind turbine in a sandy area, the monopile is a widely used foundation type under proper water depths. During the life time, monopiles are subjected to millions of cyclic loads from winds and waves and scouring around the pile is a common phenomenon, both of which can influence the operation safety of the offshore turbine. To study the coupled effects of cyclic loading and scouring on the horizontally loaded pile, a series of horizontal monotonic and cyclic loading tests on model piles were carried out in sandy soil. The influence of pile diameter, cyclic loading amplitude, and scour depth on the long-term residual accumulated displacements of a monopile is investigated. The test results show that the deformation mode of pile and the dilatancy of sand result in different static responses of the pile. A quantised work is presented to estimate the accumulated residual displacements of the pile, in which the effects of the three factors can be expressed in a united expression. Since the lateral capacity is a crucial parameter for the normalisation in regression analysis, the confirmation of a lateral capacity should be related to the corresponding concern in practical projects.

Monopile is a common foundation for offshore wind turbines. Long-term cyclic loading from winds and currents may affect the normal operation of offshore wind turbines. For offshore wind farms, natural soils are usually inherently anisotropic, and scouring often occurs as a removal of soil around a monopile. Their influence on pile behavior is seldom studied. To investigate the effects of anisotropy of sand and scouring on a cyclic laterally loaded pile, a series of 1 g model tests are conducted, in which three deposition angles of sand, two scour depths, and two cyclic amplitudes are considered. It was found that for a monopile in sandy soil, the accumulated displacements at the pile head increased with the increased deposition angles of sand and scour depth. The effects of sand anisotropy are more profound for piles with a smaller cyclic amplitude. However, the results for the pile with and without scouring did not give a consistent tendency as the factors of anisotropy of sand. Based on test results, an explicit expression is advised to assess the long-term accumulated residual displacement at the pile head, in which factors of deposition angle of sand, scour depth, and cyclic amplitudes are incorporated.