Abstract:
The development of offshore wind farms has become a feasible solution to meet the increasing demands for clean and renewable energy. However, offshore structures with fixed foundations become increasingly economically and technically unfeasible as the water depth increases. Instead, floating platforms supported by subsea anchors are a more feasible solution. Based on previous studies, deeply embedded ring-shaped anchors can be more efficient than piles and caissons because they require less material. These anchors can also be more efficient than drag anchors due to their greater embedment depth. To further understand the behavior of ring anchors in saturated sand, a series of monotonic tensile load test was performed at the University of California Davis Center for Geotechnical Modeling (CGM) at 70g. This test series investigated the effect of the loading angle and anchor embedment depth on the monotonic loading behavior. The scaled ring anchor models were constructed with stainless steel and embedded in dense saturated sand, then connected to an actuator using taut steel wire ropes. Sensors were used to measure the line tension, displacement, and inclination. The results indicate that the ring anchors mobilize the greatest capacity when they were loaded at angles close to the horizontal direction, while vertical loading leads to the smallest capacity. The anchor displacement during the tests was not coaxial with the load direction, showing a greater horizontal displacement at the earlier stages of the tests and a greater vertical displacement after the peak tensile load was mobilized. Furthermore, soil disturbance induced by the installation of the anchors was found to have a strong effect on the sand density, as evidenced by changes in miniature Cone Penetration Test (CPT) tip resistances. Overall, the results of this study further suggest that the ring anchor may be a foundation solution with greater material efficiency than other alternatives.