The suction caisson can be used in offshore wind farms. Due to the long-term horizontal cyclic loadings caused by wind, waves and currents, the offshore wind turbine foundation is required to provide high horizontal bearing capacity and limit the deflection. To better meet these needs, the skirted suction caisson, consisting of an internal caisson in an external short-skirted structure, was put forward. Numerical studies were conducted with the finite element software Z_SOIL to investigate the cyclic behavior of skirted suction caissons in sand, and the influence of cyclic load ratio, load eccentricity, loading way and loading order on the accumulated displacement and stiffness were analyzed. It was found that the soil stiffness increases at the small strain stage, the hardening small strain stiffness model was adopted. Results showed that the cyclic secant stiffness does not change significantly with the number of cycles when the cyclic load ratio is less than 0.5. However, it increases with the increase of cycles when the cyclic load ratio is larger than 0.5 due to the fact that the sand around the caisson is compacted during cyclic loading. As the increase of cyclic load ratio and load eccentricity, the cyclic secant stiffness of the skirted suction caisson reduces linearly, resulting in an increase of both horizontal and vertical displacement. It was also found that one-way cyclic loading produces the largest horizontal displacement while the two-way loading produces the largest vertical displacement. Moreover, a decreasing cyclic loading causes both the largest horizontal and vertical displacement of the caisson, which indicates that the previous cyclic loading has an important influence on the bearing behavior of the caisson.
