Abstract:To ensure the secure and prolonged operation of offshore wind turbines with rock-socketed monopile foundation, an experiment investigation is carried out to study the mechanical distinctions between such foundations and soil-based alternatives. The study involves an indoor 1 g model test to analyze the impact of stratigraphic property and loading condition on both the bearing capacity and mechanical properties of the rock-socketed pile. The research reveals that: The horizontal stiffness and bearing capacity of a rock-socketed monopile is significantly higher than that of a pure sand one with relatively a small length to diameter ratio. Under the horizontal monotonic cyclic loading, the cumulative displacement of the pile top develops rapidly in tens of cycles at the beginning, and tends to be stable in the later cycles; an equilibrium state exists for the cumulative pile-top displacement of rock-socketed monopiles. At the early stage of the cyclic loading, the stiffness of the pile foundation increases with the number of cyclic loads, mainly due to the vibrational density effect of sand, and the structural stiffness is basically stable after the sand is compacted. When the cyclic load amplitude is relatively large, the pile-rock interface is damaged and detached in the heavily weathered rock at the late loading stage, and the stiffness of the structure decreases. In the horizontal loading tests, the position of maximum bending moment of a rock-socketed monopile is always higher than that of a pure sand one, and the position of maximum bending moment of a pile decreases with the increase of cyclic loads whether the monopile is rock-socketed or not. A destructive static loading test is conducted subsequent to the cyclic loading tests, and the ultimate failure mode of the foundation obviously varies for the monopiles socketed in weathering rocks of different degrees.