Three Dimensional Numerical Modelling of Embedded Mooring Lines-Paper

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The paper presents an efficient finite-element method for modelling embedded mooring lines in three dimensions, including their response to cyclic loading and unloading. Chain links are represented by beam elements connected with rotationally free connectors, while chain–soil interaction is modelled using three uncoupled elastic-perfectly-plastic springs for axial, normal and lateral resistance.<br /><br />The method is validated against established analytical solutions for two-dimensional chains. Predicted chain profiles, attachment-point tension and inclination agree closely with the analytical results, supporting the approach’s accuracy. A three-dimensional example then examines a pre-tensioned anchor line subjected to sinusoidal out-of-plane loading. The simulations track changes in chain geometry, tension and soil resistance throughout the loading cycles. They show that the tension and chain angles depend on both applied force and line geometry, and that soil-strength gradients affect the load carried by the chain. Soil resistance also reverses or decreases during unloading, influencing the line’s residual tension and configuration.<br /><br />Unlike conventional two-dimensional analyses, this framework can represent the full three-dimensional chain shape and cyclic response. Its modular structure also provides a basis for future models with more sophisticated, coupled soil behaviour.

Keywords

finite-element method

embedded mooring lines

three-dimensional modelling

cyclic loading

beam elements

chain-soil interaction

elastic-perfectly-plastic springs

analytical validation

anchor line

soil resistance