Limit Analysis And Model Test On Bearing Capacity Of Large Diameter And Shallow Buried Bucket Foundation Of Offshore Wind Power Turbine

The offshore wind power foundation not only bears the vertical load by its weight, but also bears the horizontal load by wave, flow and the huge moment load by acting on the top of wind turbines under the normal working conditions. The large diameter shallow buried bucket foundation is a new type of offshore wind power foundation which not only bears the above loads but also has some advantages such as convenient construction and the lower cost of construction. The vertical, horizontal and overturn bearing mechanism of the large diameter shallow buried bucket foundation is different from both the circular shallow foundation without the skirts and circular pier foundation with the same height-diameter ratio, because the bucket foundation has a large diameter and the certain depth skirts around the foundation. The research is developed on bearing capacity of the large diameter shallow buried bucket foundation. The main research content and innovative achievements are as follows:(1) A three-degree freedom loading device is developed for bearing feature of the offshore wind power foundation. The vertical, horizontal and moment unidirectional loading tests are carried out under the 1g conditions on the bearing capacity of the bucket foundation, and the vertical, horizontal and moment bearing mechanism are obtained by observation tests.(2) During the research of the vertical bearing capacity of the large diameter shallow buried bucket foundation, the vertical soil damage rate is specified to define as the damage extent of the soil inner the bucket foundation. Two vertical bearing mechanisms are proposed referring to the assumptions of the Meyerhof formula and Terzaghi formula. The upper value of the vertical bearing capacity of the bucket foundation is derived according to the two failure mechanisms, respectively.(3) Combining block-based upper limit planning analysis and cylindrical coordinate finite element limit planning method, the block-based lower limit planning method is proposed. The objective function, equality constraints, and inequality constraints are established for the bucket foundation.(4) The numerical models contrast with the horizontal bearing capacity model tests are developed, and the horizontal bearing mechanism is proposed. The horizontal soil damage rate is specified to reflect the damage extent of the inner soil of the bucket foundation. The upper value of the vertical bearing capacity of the bucket foundation is derived according to the failure mechanism.(5) The numerical models contrast with the overturn bearing capacity model tests are established, and the overturn bearing mechanism is proposed. The overturn soil compression rate is specified to reflect the participation extent of the inner soil of the bucket foundation to resist the moment load. The upper value of the overturn bearing capacity of the bucket foundation is derived according to the failure mechanism.