Model Tests on Cyclic Responses of a Laterally Loaded Pile Considering Sand Anisotropy and Scouring

Abstract

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.