An Investigation into the Pull-out Failure Mechanisms of Suction Caissons

This paper reports results from an investigation into the suction caissons failure mechanisms under vertical pull-out loads. An insight to the failure mechanisms of suction caissons paves the path for developing analytical solutions to their pull-out capacity. The numerical models of suction caissons have first been calibrated by and verified against several experimental data from other researches. The verified numerical models have then been used to obtain the pull-out response of suction caissons under a variety of conditions. In the current research, as a key finding, four distinctive failure modes are introduced for the vertical pull-out of suction caissons. They vary from local modes, with caissons of low penetration in weak soils under drained conditions, to global modes, with caissons of sufficient penetration in stronger soils under undrained conditions. In general, with local modes the failure surface is close to caisson walls. With global modes, the failure surface moves away from the caisson walls and well extends in the surrounding soil. The pull-out capacity is highly reliant on the mode of the failure and on the whole it increases as the mode moves from local to global