The Kinematic Model And Theoretical Method For Predicting The Trajectory Of Drag Anchors In Seabed Soils

The penetration behavior and trajectory of drag anchors in seabed soils is notonly a complicated engineering problem, but also an research topic with lots ofscientific meanings. Nearly all the present methods that are capable of predicting thetrajectory of drag anchors need a numerical incremental computation. Based on akinematic model and a series of mathematical derivations, a theoretical frameworkfor predicting the trajectory of drag anchors is established. The concepts put forwardand described in detail in the paper are not only necessary for the theoreticalframework but also meaningful to further understanding of the engineering problemdue to clear physical background.The penetration behavior and trajectory of the drag anchor in seabed soils iscontrolled by the installation line especially the segment embedded in the soil.Correctly understanding and describing reverse catenary properties of the embeddedline is crucial for improving the drag embedment performance, precisely predictingthe anchor trajectory, and solving the positioning problem in offshore applications.The investigation on reverse catenary problems demonstrates that, the reversecatenary shape of the embedded line has to be solved almost through numericalincremental methods. In the present study, based on the mechanical model for theembedded line, the relationship between the tension and geometry of the embeddedline, and the interactional equation between the anchor and embedded line are derived.The reverse catenary equation and the expression for calculating the length of theembedded line are obtained both for soils with a uniform strength and with a linearstrength, and the position of the embedment point can be successfully solved through the derived reverse catenary equation.The model flume experiments are carried out to research the revese catenarycharacteristics of drag line in seabed soils. An experiment technique for real-timemeasuring the reverse catenary shape and capturing the embedment point is alsodeveloped. The accuracy of the developed reverse catenary equation and effectivelength equation is verified by model experiments. Experimental studies have provedthe effectiveness and veracity of the kinematic model and theoretical framework forpredicting the trajectory. The proposed kinematic model and the theoretical predictionmethoed of the kinematic trajectory may provide a new angle of view to understandthe anchor kinematic behaviors in soils, and be valuable for deterministic andtheoretical analysis of drag anchors.