The drained tension capacity of suction buckets under vertical uplift loading is calculated as the sum of friction on the inside and outside bucket wall without considering the submerged self-weight of suction buckets. When using existing methods to predict the drained tension capacity, it may be convenient to assume that the vertical effective stress along bucket walls at ultimate loading keeps the same as the initial static vertical effective stress. However, during uplift loading, the vertical effective stress was found to be reducing due to the gradually mobilized friction. This paper presents the results of finite element analyses on suction buckets in sand. The analyses focus on the distribution of vertical effective stress in the direction of bucket diameter and along the bucket wall. Compared with the initial vertical effective stress, a pronounced decrease in the vertical effective stress along the inside bucket wall is observed, but the vertical effective stress along the outside bucket wall has a minor change. The interface factor (ratio between friction stress and vertical effective stress) increases with the depth rather than a constant. Based on the numerical results, equations to predict the drained tension capacity are proposed for suction buckets in sand.
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