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 principal, with suction caissons subjected to vertical pull-out load, four distinctive pull-out failure modes have been identified. Each failure mode has been found to be related to certain categories of “soil/caisson/drainage” condition. They varied from local failure modes, with weak soils under drained conditions and caissons of low penetration, to more global failure modes, for dense sands under undrained conditions. With global modes, the failure surface has been observed to well extend in the surrounding soil. It has been noticed that as the failure surfaces shift from local modes in the vicinity of the caisson towards global modes in the surrounding soil the pull-out capacity of suction caisson increases.