Pull-out bearing behavior and failure mode of scaled suction caissons

The scaled suction caisson is a new type of the offshore mooring foundation, which can be applied to the floating structures and offshore photostatic power. A series of the inclined loading model tests are carried out on the scaled suction caisson, and the pull-out bearing capacity and failure mode at different mooring depths are investigated. The study shows that the pull-out bearing capacity increases with the increase of the inclined loading angle, but firstly increases, then decreases with the increase of the mooring depth. Compared with that of the traditional suction caisson, the ultimate pull-out bearing capacity of the scaled suction caisson increases by 8.4%, 13.6%, 41.2% and 28.6% when the inclined angle θ=20^°, 40^°, 60^° and 80^°. When the mooring depth locates at 0~0.58 times the foundation height, the failure mode of the scaled suction caisson changes from forward to the backward rotation with the increasing inclined loading angle. The backward rotation occurs in the scaled suction caisson when the mooring depth locates at 0.75~1 times the foundation height. Under the disturbance of the scaled suction caisson, the uplift and subsidence appear in the soils surrounding the scaled suction caisson in the loading and opposite direction, respectively. The range of the uplift and subsidence areas obviously expands compared with that of the traditional suction caisson. The results demonstrate that more soils can be mobilized by the scaled suction caisson to resist the external loads. Based on the calculation model by proposed by Liu, the formula calculating the pull-out bearing capacity of the scaled suction caisson located at optimum mooring depth is proposed. The predicted pull-out bearing capacity using the proposed method agrees well with the model test results.