Reverse Catenary Equations Of Drag Lines And Application To The Kinematic Model Of Drag Anchors

A drag line can be divided into three elements: catenary line in water, horizontal line on the seabed and embedded line in soils. Research results indicate that reverse catenary of embedded line in the seabed is the direct and key factor affecting the draging performance of drag anchor. This thesis aims to establish an analytical reverse catenary model in general marine soil, which is applied to predictive model for kinematic trajectory of drag anchor to solve the trajectory equation.The relation between tension and geometry of embedded line is developed by analyzing the line-soil interaction with limit equilibrium theory. On this basis, a study is conducted to line-anchor coupling theory, and equations are derived for estimating geometry of reverse catenary and length of embedded line. A parametric analysis is performed systematically to study the effects of soils and drag line on emdedded line tension and reverse catenary geometry. In order to check the applicability and precision, the simplified equations of this thesis and Neubecker are compared with the precise numerical solution.A model for kinematic trajectory of drag anchor, being suitable to general marine soil, is set up by applying the equations of reverse catenary and length of embedded line to the analytical framework. Based on the above framework, this thesis derives the related elements in the model, including embedment point, equivalent length, equivalent angle and drag distance, and finally solves the kinematic trajectory equation. A parametric analysis is performed systematically to study the effects of soils, drag line and anchor properties on trajectory. In order to check the applicability and precision, the simplified trajectory equation is compared with the precise numerical solution and other prediction methods.