Study On Centrifugal Model Test Of Vertically Loaded Anchor With A Bridle Shank

Vertically loaded anchor(VLA)is a new type of deepwater offshore mooring foundations,it has some advantages like convenient installation,low cost,high bearing capacity and convenient recycling and other characteristics.The bridle shank of vertically loaded anchor consists of front and back shank and angle adjuster.The bridle shank will be reconfigured in the installation and loading process.The ratio of front and back shank will impact the stable states of the bridle shank in the installation and loading mode and the impact is not clear.On the other hand,the vertically loaded anchors and offshore platform are tightened firmly by mooring line,the angle between the mooring line and horizontal direction is called mooring angle and the influence of different mooring angles to bearing capacity of the vertically loaded anchor in the loading process is unclear.Therefore,the research content of this paper is to study on the the installation trajectory and installation load in the installation process,and on the mooring bearing capacity and bearing capacity performance in the loading process of the VLAs which are influenced by the ratio of the front and rear shanks and the different mooring angles.The research method of this paper is doing drag installation test and mooring test of the VLAs by using the centrifugal simulation technology and the vetically loaded anchor model which is same like the prototype of Stevmanta VLAs.The installation trajectory,installation load and mooring bearing capacity will be measure in the test process.By analyzing the results of the comparative test,the effects of the ratio of 0.7,0.8,0.9,1.0 and different mooring angles of 30°,60° and 90° on the installation and mooring bearing capacity performance were investigated.By comparing the installation and mooring process,the following results are obtained.For the installation trajectory,the penetration depth and the peak angle of the anchor plate increased gradually when the ratio of the front and back anchors increased from 0.7 to 1.0,and the VLAs are more conducive to installation penetration.In the installation test,the same ratio of front and back shank of the VLA installation curves have a high repeatability.The installation load increases as the horizontal drag distance increases.The installation load factor is generally reduced as the horizontal drag distance increases,and the final installation load factor is gradually increased as the ratio of the front and rear shank increases at the end of the installation.In the mooring test,the mooring bearing capacity corresponding to the different mooring angles of the same front and rear shank gradually increased with the increase of the drag distance and reached the maximum mooring bearing capacity,and then the mooring bearing capacity gradually becomes smaller.The ultimate bearing capacity is relatively close for the different mooring angles of the same front and rear shank,which verifies that the vertically loaded anchor can bear the load in any direction through the structural deformation in the mooring stage.The range of bearing capacity performance ratio(the ratio of ultimate bearing capacity to maximum installation load)of different mooring angles is 1.08 ~ 2.67,most of which is concentrated in the range of 1.50 ~ 2.50.The installation and loading process of the vertically loaded anchors is a more complex process involving multiple factors,Different ratios of the front and back shank and mooring angles have a significant effect on the installation trajectory and penetration depth,installation load,ultimate bearing capacity and load bearing capacity and so on.These factors affect each other.It is necessary to consider the effect of different ratios of front and rear shank and mooring angles on the various factors and choose a more appropriate ratio of front and rear anchors and mooring angle.