Study On The Bearing Capacity Of Suction Anchors With Taut Mooring System In Soft Clay With The Strength Increase Along The Depth

With the increasing of human demand for oil and gas energy, marine oil and gasproduction gradually toward deep water, suction anchors with mooring system as anew deep-water marine platform, has been used recently. Currently, the study on thefailure mode and bearing characteristics of the suction anchor under static loading andunder static loading with cyclic loading in soft clay where the strength increase alongthe depth were lack of relatively. This article will solve this problem through modelexperiments and numerical simulation study.First of all, we prepared the soil clay where the soil strength increased linearlywith depth by vacuum layered preloading method. In the preparation process, we onlyset geotextile in the bottom and do not set drainage boundaries around the soil box,this can reduce the formation of a hard shell of the surrounding soil, thereby reducingside effects.Secondly, in the soil clay whre strength increased linearly with depth, study onthe failure modes of suction anchor under static loading by model tests. When theslope of load-displacement curve close to zero, the corresponding external load is theultimate bearing capacity required, size corresponds to the carrying capacity of themooring point displacement along the direction of the mooring is defined as thefailure criterion, we need to use different failure criterions to determine the ultimatebearing capacity for different failure modes, and in accordance with this standard, theultimate bearing capacity is more consistent with the theoretical calculated value.Aspect ratio and the loading direction change on the anchor bearing characteristics arenot consistent in the different soil layers, when the anchor for the vertical destruction,the carrying capacity depends on the vertical resistance of the anchor; when theanchor for the horizontal destruction, the carrying capacity depends on the horizontalresistance of the anchor.Again, in the soil clay where the soil strength increased linearly with depth, wearranged a series of model tests under average and cyclic loading. The experimentsshow that if the anchor was vertical destruction under static load, then it will also bevertical destruction under average and cyclic loading; if the anchor was horizontaldestruction under static load, then it will also be horizontal destruction under average and cyclic loading. However, with the increase of cyclic loading ratio, the angledirection of the movement of the anchor increases gradually and are larger than thestatic bearing capacity model tests it means that the degree of weakening on verticalresistance of the suction anchor is greater than the degree of weakening on the level ofresistance by cyclic loading, and with cyclic loading ratio increases, the weakeningdifference was more obvious. Compared the test results in soil clay where the soilstrength increased linearly with depth and uniform constant soil, we know that when aload direction and the average load was given, the soil conditions change had nosignificant effect on cyclic bearing capacity ratio.Finally, in the soil clay whre strength increased linearly with depth, we take thefinite element method to analysis the bearing capacity of suction anchors with tautmooring system, the selection of the contact model and the elastic modulus areconsistent with the soil clay whre the strength are the same with depth, The resultsshow that the finite element results agree well with the model results.