Study On Design And Security Of Large-diameter And Wide-shallow Bucket Foundation For Offshore Wind Power

Development of renewable energy is a trend in the world. Offshore wind resource has lots of advantage, such as rich, no occupating cultivated land, away from residences, little noise. All countries compete to develop it. But it is difficult to survey the geological conditions of seabed. Sea currents, waves, sea ice, ie, environmental loads are complex. That makes it difficult to construct infrastructure of offshore wind power, and high cost, high maintenance costs. How to reduce the cost and construct conveniently? This becomes the key technology of foundation design for offshore wind power. It is also the main problem and difficult to ensure offshore wind power foundation security in all kinds of environmental loads. In view of the development stage of offshore wind power in our country, it is planning to construct coastal and shallow beach wind power. Previous large-scale piling pile equipment for marine platform construction is difficult to access. This paper considers that the bucket foundation is constructed fast, reusable and easy to be constructed at the gap of bad weather. Taking the seabed foundation need of ballast stability and anti-erosion into account, the paper combines bucket foundation with gravity foundation, raising large-diameter and wide-shallow bucket foundation. With the great moment for the offshore wind power infrastructure, it is larger diameter used in coast and beach than previous any bucket foundation. This structure is comprehensively researched in the paper. The study field is divided into the three aspects as follows:(1) Proposing a system calculation method for large-diameter and wide-shallow bucket foundation using in coast and beaches. Presenting two types of simplified calculation of bucket foundation capacity and structural design pattern -- bucket foundation with its wall bearing and bucket foundation with its top bearing for the first time. Studying fuilare mode of large-diameter wide-shallow bucket foundation in saturated sand and bearing capacity of three-dimensional model with the finite element method to verify the feasibility of theoretical simplified calculation.(2) The SQP optimization method and the improved genetic algorithm are applied to the overall size optimization of bucket foundation design, with the goal of capacity safety factor for the first time. To meet the need of foundation strength, stiffness and stability, the shape optimization and topology optimization with the finite element method are used to local optimization of the large-diameter bucket foundation transmission system design for the first time, saving a huge amount of investment in project.(3) Based on fluid-soild coupling, solid-soil coupling and nonlinear contact theory, the soil-bucket foundation-tower-simplified wind generator model is built. The first time finite element- discrete element ALE method is applied to analysis security of large-diameter and wide-shallow bucket foundation with limit static load and random wind, waves, currents of the coupled dynamic load, fully reflecting the force mechanism and working condition of bucket foundation. Meanwhile, the paper establishs security assessment system for offshore wind power bucket foundation.