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.