Investigation of Pullout Capacity Characteristics of Suction Anchors Under Inclined Loads in Layered Soil

Suction anchors are widely used in marine engineering because of their easy installation, cost-effectiveness, and excellent load-bearing capacity. However, existing research on their bearing capacity has primarily focused on homogeneous soils, which fails to adequately reflect the actual bearing capacity of layered seabed soils. Therefore, this study conducted a series of numerical simulations to investigate the pullout bearing capacity of suction anchors subjected to inclined loads in upper-stiff–lower-soft layered clay. By considering the clay strength (Sum/kD) and soil layer thickness ratio (Th/L, Tc/L), this study systematically explores the influence of the optimal centerline loading depth (Zcl,opt), uniaxial ultimate bearing capacity (Hult and Vult), and the VH failure envelope of suction anchors. The results indicate that the layer thickness ratio Th/L of lightly overconsolidated clay (LOC) is the key factor influencing the Zcl,opt and ultimate bearing capacity Hult and Vult. An increase in Th/L significantly enhances the pullout resistance of suction anchors, which primarily results from the combined enhancement effect of lateral friction resistance and end resistance at the anchor–soil interface. The layered clay has a distinct influence on the horizontal and vertical bearing capacities of suction anchors. Based on the results of parameter analysis, a conservative analytical expression for the lower bound of the VH failure envelope curve is further proposed. The research conclusions provide a theoretical basis and engineering practice guidance for the optimized design and safety assessment of suction anchors in layered soil.