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 point. A parametric study was conducted for evaluating the effects of the depth of the attachment point, internal friction angle of sand, submerged unit weight of sand, angle of the mooring line at seabed, mooring line self-weight, and mooring line nominal diameter. The results of parameter study can be significant information for applying the developed analytical method in practice. The present study demonstrates that the developed analyti-cal method is effective for analyzing the behavior of mooring line embedded in sand, and it can help to design anchor effectively and economically.
계류 시스템은 앵커, 계류선, 그리고 해상구조물로 구성된다. 석션, 드래그 앵커는 해저 지반 아래에 설치되며, 앵커에 연결된 계류선의 일부 역시 해저 지반 아래에 매립된다. 본 논문은 모래지반 아래에 매립된 계류선이 앵커에 미치는 영향을 분석하였다. 모래의 마찰 저항력과 지지 저항력을 고려한 해석적 방법을 제시하였으며, 개발된 이론 식을 통하여 계류선을 통해 앵커에 전달되는 하중과 하중방향, 그리고 모래지반에 묻힌 계류선 전체의 형상을 예측하였다. 지반 상태에 따른 매립된 계류선의 거동을 분석하기 위하여 원심모형 실험을 수행하였다. 계류선에 작용하는 하중을 측정하기 위하여 소형 하중 측정 장치를 개발하였으며, 수평과 수직 방향의 하중을 측정할 수 있는 연결장치를 이용하여, 앵커에 전달되는 하중과 경사각을 계측하였다. 실험 종료 후, 시료를 조금씩 제거하여 계류선의 형상을 기록하였다. 실험 결과는 지반조건에 따른 계류선의 거동차이를 명확히 보여주었다. 개발된 이론 식에 의해 예측된, 모래지반에 묻힌 계류선의 거동은 원심모형 실험 결과와 매우 유사하였으며, 단순화된 이론 식과의 비교 역시 동일한 결과를 얻었다. 개발된 이론 식을 바탕으로, 변수연구를 통하여 모래지반에 묻힌 계류선의 거동에 미치는 영향인자들을 분석하였다. 본 연구를 통하여 개발된 이론 식은 모래지반에 묻힌 계류선의 거동을 분석하는데 효율적이며, 이를 통하여 모래지반에 관입되어 설치되는 앵커를 효율적이고 경제적으로 설계 할 수 있다.
