Experimental Study On Drag Chain Behaviors In Saturated Clay

The anchor chain is an important part of the deep-water mooring system.Under the action of drag force,the movement of the anchor chain directly influences the bearing capacity and installation of the mooring system.Therefore,it is important to study the movement of the drag anchor chain in the soil for the design of the deepwater mooring system.This thesis is financially supported by the National Natural Science Foundation of China(Nos.51274079,Nos.51574139),Hebei Province Natural Science Fund Project(Nos.E2015208089)and Hebei Province graduate student innovation funding project(CXZZSS2017097).In this paper,the setup composed of the iron frame,model box with bottom welded hook,dragging device,force and deformation tester system was self made.The setup was employed to observe the drag behaviors of the drag chains with the chain diameter of the 4mm,5mm and 6mm in saturated clay.The effects of anchor diameter,initial mud angle and drag force on the morphology of anchor chains in saturated clay were investigated.The tested results were compared with those predicted by Neubecker and Randolph anchor chain equations,and the parameters influencing the anchor chain equation are analyzed.Our main conclusions are in this paper:1)If the anchor chain diameter increases,the resistance between the soil and the chain increases,and the pad-eye tension and the horizontal displacement of the anchor chain decreases.2)Under the condition of enough drag force,the trajectories of drag chains with different diameters in clay are basically same.3)The larger the initial mud surface angle is,the greater the pad-eye tension is,and the smaller the resistance between the soil and the chain and the horizontal displacement of the anchor chain are.4)When the mud surface angle is small,the test trajectory curve is nearer to the predicted trajectory curve,which indicates that Neubecker and Randolph’s anchor chain equation can predict the behaviors of the anchor chain in saturated clay when the initial mud angle is small.5)When the mud surface angle is larger,the predicted result of the anchor chain equation is somewhat different from the experimental result,which is mainly attributed tothe simplification in the calculation of the Neubecker and Randolph anchor chain equations...