Centrifugal shaking table tests and seismic response analysis of suction caisson foundation in saturated clay

The shallow seabed in China's offshore wind farms is primarily composed of soft clay that can exhibit remarkable cyclic softening and deformation accumulation. Accordingly，suction caisson foundations and the supported superstructure can show excessive displacement accumulation under seismic loading，and thus threatening serviceability of wind turbine. This works conducts centrifuge shaking table tests for turbine supported by single caisson and multi-caisson jacket foundations in undrained clays，and constructs corresponding numerical model based on an undrained total stress-based constitutive model for cyclic loaded clay accounting for small-strain stiffness. The numerical model was validated against experimental data. By using numerical simulations，this work studies the effects of foundation types on the acceleration and deformation response of wind turbine superstructure under seismic loading. The relationships between turbine seismic response and filtering frequency-contents of earthquake loading via foundations are explored. This study shows that the proposed numerical model can reasonably capture the seismic response of suction caisson foundation and superstructure. There are strong correlations between magnitude of turbine tower accumulative displacement and its vibration intensity during earthquake. When featuring similar static loading characteristics，compared to single-caisson foundation，multi-caisson jacket can filter certain higher-order frequencies of seismic loading，and thus leading to smaller superstructure acceleration and consequently lower cumulative displacements.