Seismic analysis of a suction caisson foundation for offshore wind turbines
YANG Chunbao1,2, ZHANG Jianmin1,2, WANG Rui1,2
1. Institute of Geotechnical Engineering, Tsinghua University, Beijing 100084, China;
2. State Key Laboratory for Hydraulic Engineering, Tsinghua University, Beijing 100084, China
Abstract：The stability of suction caisson foundations during earthquakes is evaluated for a typical suction caisson foundation of an offshore wind turbine located in a sandy seabed in the North Sea. The analysis was a unified plasticity model for the large post-liquefaction shear deformation of the sand and a three-dimensional dynamic finite element analysis to predict the seismic deformation and overturning probability during an earthquake. The analysis shows that the foundation experiences horizontal oscillations that lead to large deformations. The caisson slants with the rear moving up. The overturning probability keeps increasing and the angle eventually reaches more than 0.8°, which exceeds the safety limit. The rotation center constantly changes and the seabed pore pressure increases. Negative pore pressures can develop inside the caisson which enhance the overturning probability, but then dissipate. The seabed liquefaction depth is about 3 m, so the front of the caisson pierces into the seabed. Consequently, seabed liquefaction aggravates the deformation and overturning probability which affects the system operation.
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2017, Vol. 57 
