Characterization of mooring line behavior embedded in sand via centrifuge model test

Abstract

Mooring system consists of anchor, mooring line, and offshore structure. When the anchor is installed, embedded in seabed, a portion of mooring line is also embedded. The embedded part of mooring line affects the anchor’s capacity in two ways. This paper presents a method for calculating mooring line’s tension and inclina-tion of angle at the attachment point and the overall configuration of mooring line embedded in sand. The analyt-ical method was developed considering both the soil frictional resistance and the bearing resistance, and also effective width where the soil resistances act. To confirm the developed analytical method, a number of centri-fuge tests were performed at two anchor depths, while maintaining relative densities of 76% or 51% in the cylin-drical test box with clean sand. A 2.4 mm wire was used as the mooring line, and a miniature load cell was de-veloped to measure tension in the wire. The model of anchor was a box (2 mm in lengths) equipped with hori-zontal and vertical miniature load cells, and it could measure horizontal and vertical load component at the at-tachment point. The test results involve tension and inclination angle of wire, and overall configuration of em-bedded part of wire. The centrifuge test result showed different behaviors of embedded mooring line depending on the test conditions. Comparisons of the test results with the results of the analytical solutions showed good agreement in load and its angle at the attachment point, and overall configuration of embedded wire. The devel-oped analytical method was also compared with simplified method. The simplified method can be applied to any soil types, but it requires load and its inclination angle at the attachment point. The developed analytical meth-od’s results was used in the simplified method. The comparisons between developed analytical method and sim-plified method are shown in good agreement in overall configuration, load, and its inclination at the attachment poin...