A new Offshore Mooring Anchor for Hard Grounds

This paper presents the development and the testing of a new anchor for hard seabed conditions. The anchor development involved computer modelling, laboratory scale model testing, and eventually the full scale anchor testing offshore. The goal of the development was to expand the suitability and applicability range of drag embedment anchors in hard soils and soft rocks. The anchor development process is explained and the theoretical models for hard ground anchoring are introduced. The laboratory testing conditions and the results of laboratory tests are presented. Following the model scale qualification phase in different soil types and strengths in the laboratory, the full scale testing of the new anchor is carried out at selected offshore locations. The offshore testing conditions, the instrumentation and measurement techniques, and the results of offshore testing are evaluated and presented. In order to benchmark the performance of the new anchor, both laboratory tests and field scale tests are run against a reference anchor which is tested under the same conditions. The model scale and field scale testing results show that the new anchor is able to penetrate into harder grounds and generate substantial holding capacity. The penetration ability and the stable holding capacity of the new anchor is around 22% to 47% higher than the existing anchors of comparable category. The offshore scale test results have proven that the new anchor has increased the offshore mooring capability in hard soils and soft rocks. It is expected that the results of this work will allow a better understanding of anchor behavior in hard soil and soft rocks. The results and the technology developed will be beneficial to the oil/gas and energy sectors in general and the offshore mooring industry in particular. The new technology is expected to provide a practical and cost effective anchoring solution in challenging frontier areas (e.g. Arctic, Northwest Shelf Australia, Persian Gulf, and many shallow water areas of the world), and in emerging industries like Floating Renewables and dredging/offshore construction.