The tripod bucket jacket foundation is proven to be a practicable solution for offshore wind turbines (OWTs) to withstand huge environmental loads in deep water. This paper presents model tests for a scaled tripod bucket jacket foundation with reference to a prototype applied in China to obtain its lateral load bearing behavior in medium-dense sands. Extended finite element analyses were conducted by ABAQUS to compare anti-overturning responses for the tripod bucket foundation in both sand and soft clay, and the influences of loading direction and aspect ratio were also taken into account. The results showed that the failure modes of the laterally loaded tripod bucket foundation are the pull-out of the windward bucket in sand and the settlement of the leeward bucket in soft clay, respectively. Thus, the unfavorable loading direction of the foundation changes with soil type. It is also shown that the bearing capacity for the foundation in soft clay will be enhanced more effectively as the bucket diameter increases. Instead of the rotational soil resistance resulting from the rotation of the bucket, the vertical soil resistance governs the anti-overturning bearing capacity of a tripod bucket foundation. As the tilt created by the overturning moment rises, the rotational stiffness of the foundation dramatically declines.

The complex-load environment of offshore monopile foundations makes the combination of waves and current, and the variation in water depth, important factors for local scour. A flume test model of flow–pile–soil coupling for large-diameter monopile foundations is established, which comprehensively considers the combined reciprocating action of wave/current and the influence of tide depth. The precision of the experiment is ensured by the extension method of series models. The results show that the local scour caused by tides and the wave–current combination is obviously different from the unidirectional wave–current combination. The equilibrium scour depth obtained by the test is found to have some deviation from the predicted scour-depth equation. The maximum scour depth decreased with the increase in water depth within the range of 3 to 6 times the pile diameter. The bed shear-stress equation was generally consistent with the scouring-depth rule measured by the model, which can be considered to evaluate the rationality of the test results.