Search Results (5)

In the marine environment, the suction caisson foundation (SCF) is often subjected to combined inclined and cyclic loading from wind and waves, which may significantly affect its ultimate bearing capacity. Under combined loading conditions, the evolution of ultimate bearing capacity is influenced by multiple factors, and the corresponding bearing capacity envelopes have become key issues that urgently need to be addressed. In this study, a series of model tests and numerical simulations were conducted considering the effects of load inclination angle, loading position, aspect ratio, soil undrained shear strength, and interface friction coefficient. The results show that under static loading conditions, as the loading depth increases, the load inclination angle corresponding to the maximum bearing capacity decreases from 45° to 0°. As the cyclic load ratio and static load ratio increase, cyclic loading significantly intensifies displacement accumulation and the degradation of ultimate bearing capacity. As the loading depth increases, the failure mechanism transitions from rotation-dominated to translation-dominated behavior. In addition, the ultimate bearing capacity increases monotonically with increasing aspect ratio, interface friction coefficient, and soil undrained shear strength. A normalized V–H bearing capacity envelope was established, which shows good agreement with the experimental and numerical results. By introducing a cyclic bearing capacity degradation coefficient, a modified envelope was proposed to describe the evolution of ultimate bearing capacity under cyclic loading conditions. The bearing capacity evolution patterns and envelope method proposed in this study provide a useful reference for the engineering design of SCF. Full article

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 (S_um/kD) and soil layer thickness ratio (T_h/L, T_c/L), this study systematically explores the influence of the optimal centerline loading depth (Z_cl,opt), uniaxial ultimate bearing capacity (H_ult and V_ult), and the VH failure envelope of suction anchors. The results indicate that the layer thickness ratio T_h/L of lightly overconsolidated clay (LOC) is the key factor influencing the Z_cl,opt and ultimate bearing capacity H_ult and V_ult. An increase in T_h/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. Full article

The addition of fins to suction anchors has been proposed to enhance bearing capacity in combined loadings. This study examines the failure envelope of finned suction anchors subjected to combined vertical–horizontal loadings in normally and lightly over-consolidated clay using the finite element method, focusing on fin capacity enhancement and fin efficiency against penetration resistance. Parameters considered include different length-to-diameter ratios of the suction anchor, as well as different fin-to-shaft-length ratios, to evaluate the effect on capacity. The addition of fins expands the vertical–horizontal failure envelope, minimally altering the shape of the failure envelope. The fin factor (the ratio of the finned suction anchor capacity to the conventional suction anchor capacity) increases with fin lengths but exhibits minimal dependence on length-to-diameter ratios. A nonlinear relationship between fin length and fin factor (both vertical and horizontal) with a distinct trend is observed in horizontal capacity. Fin efficiency (the ratio of capacity to penetration resistance) decreases with increasing fin length except at a fin length-to-shaft ratio of unity in horizontal capacity. Full article

Skirted anchors are often used as temporary or permanent anchoring foundations for underwater pipelines and floating platforms. A series of model tests and finite element simulations were conducted to study the bearing capacity of square skirted anchors with different mooring points. Based on the test results, two failure modes of square skirted anchors with different mooring points were analyzed. It was found that, when the mooring point was located at the top of the side skirt, the square skirted anchor was more prone to rotation and had a lower bearing capacity. The numerical method was validated by the model tests. In total, 140 numerical calculation results show that, when the mooring point position (normalized depth of mooring point) h/H = 0.5~0.75 and the load inclination angle θ = 0°~30°, the bearing performance of the square skirted anchor is optimal. As the aspect ratio of the square skirted anchor (H/B) increases from 0.25 to 2.0, the optimal mooring point position h/H moves downward from 0.5 to 0.75. The failure envelopes in the V-H loading space of the square skirted anchor were drawn, and the corresponding fitting equation was obtained. Full article

The applications and studies of gravity anchors in the ocean are becoming more and more extensive. Most of the research, however, has been directed toward the bearing properties of sand. Relatively less attention has been paid to the bearing properties of gravity anchors in clay. Clay is widely distributed on the seabed. The research on the bearing capacity of gravity anchors in clay is of great significance for offshore oil exploitation. Therefore, the gravity anchor was investigated by conducting reduced-scale model tests, and the bearing process of gravity anchors in clay was simulated through a 3D finite element method. Model tests and numerical simulations were used to determine the capacity curve and the V-H failure envelope of gravity anchors in clay. The simulation results and the test results are in good agreement. The failure form of the gravity anchor in clay was revealed by 3D finite element analysis. The effect of cohesion, internal friction angle, and mooring point height on bearing capacity have been studied. The influence of the height of the mooring point on the V-H failure envelope curve was explored by changing the height of the mooring point. The formula of the V-H failure envelope curve suitable for different mooring point heights was obtained. Full article