Model tests on bearing capacities of suction anchors with taut mooring systems under combined static and cyclic loads

Load-controlled model tests are conducted to study the bearing capacities of suction anchors with taut mooring systems under combined static and cyclic loads at the optimal loading point using an electric servo loading apparatus developed by the authors. Failure modes of anchors, effects of static loads on cyclic bearing capacities and variations of cyclic bearing capacities with the number of cycles to failure are analyzed based on test results. The following conclusions are drawn. Failure of anchors is the translational failure mode of pullout from the soft stratum if the vertical ultimate resistance acting on anchors is less than the lateral one acting on anchors under combined static and cyclic loads. The displacement along the mooring direction at the loading point is about 0.6 times the anchor diameter when anchors are in the ultimate states under static loads. The cyclic bearing capacity of anchors increases with the increase of static load ratios and the cyclic load withstood by anchors also depends on static load ratio for a specified number of cycles to failure. The cyclic load withstood by anchors is the maximum when the static load ratio is about 0.5. Cyclic bearing capacities of anchors decrease with the increase of the number of cycles to failure for a specified static load ratio. The effect of loading directions on the variation of the cyclic bearing capacity with the number of cycles to failure is not obvious when the loading direction varies from 30 to 40 degrees for a specified static load ratio. The cyclic bearing capacity of anchors is not less than 75% of the static bearing capacity if the static load ratio is greater than 0.5 and the number of cycles to failure is less than 1000.