Bearing behavior of wide-shallow bucket foundation for offshore wind turbines in drained silty sand

The failure mode of the wide-shallow bucket foundation is different from that of the traditional suction caisson and the narrow-deep bucket foundation. Results from elasto-plastic analyses of 3D finite element models are presented, aimed at defining the shape of the yield envelope in the V-H, V-M, H-M and V-H-M spaces and the failure mode of the bucket foundation. The compressive bearing capacity of the wide-shallow bucket foundation was determined by the displacement. The corresponding load under a vertical displacement of 0.06D was the vertical ultimate bearing capacity. The vertical loading had an amplification effect on the horizontal load-bearing and moment capacity, and the horizontal loading which was in the opposite direction to the moment increased the moment capacity by 20-40%. New simplified calculation methods were proposed for the vertical load-bearing capacity and the overturning stability. In the proposed method, the vertical capacity consisted of a top plate resistance of the bucket and a side frictional resistance. The overturning stability was determined by the safety factor method, and depended on the location of the rotation point. A comparison between results from the finite element analysis and the simplified calculation methods showed that the proposed equations properly predicted the capacities of the wide-shallow bucket foundations.