An experimental investigation on the performance of shared pile anchor in saturated sand for floating offshore wind turbines

High cost remains the most important obstacle that hinders the development of the floating offshore wind industry. The adoption of shared anchor technology in large-scale floating offshore wind farms can significantly reduce the number of anchor points, thereby lowering the cost for the mooring system. Typhoons are the main marine environmental challenge for constructing floating offshore wind farms along China's Southeastern coast, yet there is no established methodology for designing shared anchors under such conditions. To shed light on the bearing characteristics of shared pile anchor under typhoon conditions, results of a series of model tests are reported in this paper. The experiments reveal that shared pile anchors manifest progressive accumulation in horizontal and vertical displacements under cyclic loading, and ultimately fail due to gradual extraction from the seabed. Under typhoon conditions, the continuously evolving resultant loading direction causes a multi-directional loading effect that can significantly accelerate the displacement accumulation rates. The effect depends critically on the cyclic loading level, the magnitude and abruptness of loading direction evolution. When the peak load under cyclic loading is no greater than 50 % of the monotonic holding capacity, the multi-directional loading effect can be practically ignored. The implications of the test findings to shared pile anchor design in sand are discussed and design guidance is provided. • Model tests are performed to investigate failure mechanism and load-displacement response of shared pile anchors in sand. • Cyclic loading effect with continuously evolving resultant loading direction, simulating typhoon conditions, is examined. • The tests reveal significant beneficial coupling effect of horizontal load to vertical capacity of anchor piles in sand. • For peak load less than 50 % F u , the cyclic loading effect with continuously evolving loading direction can be ignored.