Numerical studies on soil-skirt roughness and sand plug impact in bearing capacity prediction of caisson foundations subjected to the uniaxial loads

Skirted foundations denoted as suction caissons are becoming an increasingly prevalent offshore foundation solution for either the oil and gas industry or renewable energy infrastructure. Their response to combined vertical, horizontal, and moment loading must be found to ensure their stability under harsh environmental conditions. As part of this process, knowledge of uniaxial capacities is required. Previous studies have neglected the effect of deformable ground by assuming that the soil within skirts behaves rigid during drained loading, but this assumption needs rigorous studies. A series of 3-D finite element analyses has been conducted to investigate directly how the skirt geometry, soil–skirt interface roughness, and deformable plug within the skirt compartment affect the drained skirted foundation capacity and depth factors under uniaxial loading. The results show that the foundation embedment, interface friction, and soil plug placed within the skirt significantly influence the accompanying mechanisms occurring at failure and therefore the uniaxial capacities. The finite element analyses under uniaxial loads are performed for the rough and smooth interface assumptions, to show how the roughness interface influences the ultimate bearing capacities and depth factors and the corresponding failure mechanisms in different soil profiles.