Lateral ultimate bearing capacity of modified suction caisson in uniform and linearly increasing strength undrained clays

Abstract The modified suction caissons (MSCs) have a cylindrical external skirt surrounding the top of the traditional suction caisson to increase the horizontal bearing capacity. MSCs will be subjected to inclined lateral loadings for anchoring offshore floating facilities, and the maximum lateral bearing capacity will be reached when the loading direction passes through the rotation center of the MSCs to generate horizontal translation in the seabed. This paper proposed an analytical model consisting of a meniscus failure wedge near the mudline and a purely lateral flow‐around mechanism in deeper soil for MSCs moving laterally in clays. The upper‐bound analysis is conducted to obtain the ultimate bearing capacity of MSCs by optimizing only one parameter to approach the critical failure mechanism that offers the minimum energy dissipation. The influences of the external skirt length ( L ) and radius ( R ) and adhesion factor ( λ ) at the caisson‐soil interface on the bearing capacity of MSCs are investigated. The finite element limit analysis (FELA) results are used to verify the rationality of the presented failure mechanisms and upper‐bound predictions. It is proved that the presented upper‐bound analyses can well predict the lateral ultimate bearing capacity of the MSCs with a horizontal translation failure.