Failure mode and capacity of suction caisson under inclined short-term static and one-way cyclic loadings

In addition to the loading angle at the pad eye, the types of applied forces will affect the failure mode and the capacity of suction caisson in a soft clay seabed. In this study, a specially designed platform was used to perform model tests with different loading angles and cyclic parameters. First, the short-term static capacities and the failure modes for the typical inclined loading angles were studied, and then the influences of cyclic amplitude, number of cycles and cyclic period on the subsequent failure mode, and caisson capacity were investigated by applying a series of one-way cyclic loadings. The experimental results showed that when the loading angle decreases from 50.2° to 32.0°, the model caisson’s failure mode changes to a combined mode consisting vertical motion, horizontal motion, and anticlockwise rotation, and its corresponding capacity noticeably increases. However, the increases in amplitude, number, and frequency of the previous cyclic loadings would turn this combined failure into a dominant vertical pullout and reduce its capacity to some degree. Therefore, the influence of the previous cyclic loadings should be taken into account to accurately estimate the holding capacity of the suction caisson.