Cyclic accumulation effects at foundations for offshore wind turbines

Offshore wind turbines will reach their serviceability limit at a certain permanent inclination of the structure, which can be caused by a strong storm event. If the permanent deformation after such an event is sufficiently large, the allowed range for the operation of the turbine may be exceeded. Self-healing means that this permanent inclination can at least partly be reverted by a rather regular exposure to wind and waves with smaller amplitude. The ability of the system to show this behavior depends on the design of the foundation and the type and state of subsoil. This paper focuses on shallow foundations on dense to medium dense sand. The setup for an experimental investigation of this phenomenon in small scale model tests is presented in detail. It can be shown that the tests confirm the self-healing ability of foundations exposed to cyclic loading. The influence of the loading sequence is also presented