Movement Direction Of Drag Anchors In Seabed Soils

Drag anchor is an important element in deepwater mooring systems. But there are some difficulties in accurate positioning in the field application. It is significant to exactly predict the kinematic trajectory of drag anchors in seabed soils. The movement direction is one of the important kinematic characteristics of drag anchors, which provides a base on the research of the anchor kinematic trajectory and the ultimate embedment depth etc. Until now, this subject is undeveloped in the world. The data about the direction of movement in theory and experiment are limited. Worse more, the conclusion is uncertain.Two research methods of the anchor movement direction——the theoretical analysis and the model experiment have been adopted. Firstly, a theory based on a new force model has been developed. These equations are self-contained deduced on the principle that the force applied to the chain needed for movement in the seabed is the least in the movement direction. The specific results are gained through the theory. Furthermore, drag anchors of general geometry, such as wedge and rectangle, have been given their movement directions in theory both in clay and sand. Finally, the effect of related parameters on the expressions has been investigated by changing the value of them. This theory, which can be applied on any anchor in any type of soil, is significant for the research in the field.Meanwhile, the model experiment of drag-anchors has been designed and developed in the existing model flume to test movement direction. In this paper a new testing procedure has been presented and a series of tests have been conducted using this procedure which applied to the four different model anchor types. Firstly, a group of kinematic trajectories is iterative computed through the collected data by sensors. Then it is compared with the trajectory gained by the manual measurement technique. Finally, mean relative error of the case clearly shows the movement direction of the drag anchor. The theory results have been certified by the model experiment. Additionally, the testing procedure can be applied to any laboratory model experiments and filed applications, which is great significant to the following research.