Lateral response of monopile supporting an offshore wind turbine

One of the geotechnical challenges for a monopile-supported offshore wind turbine is to create a foundation design procedure that incorporates the effects of cyclic loading from wind and waves in a safe and easy way. Improved procedures may enable the use of monopiles on deeper waters, but still secure a robust and cost-beneficial foundation design. In order to develop new design procedures it is essential to understand the pile–soil interaction. With centrifuge tests as the basis, this paper discusses the effects of the soil–pile interaction, with the focus on accumulation of displacements and change in secant stiffness in dense sand. Hence a centrifuge test series simulating idealised cyclic loads on a monopile supporting an offshore wind turbine was carried out. The validity of these centrifuge tests is discussed, and a simple design procedure is presented for prediction of the accumulation of displacements and change in secant stiffness based on the results from the centrifuge tests.