【作者】 朱明；

【导师】 张燕； 叶剑红；

【作者基本信息】 武汉理工大学 ， 安全工程（专业学位）， 2024， 硕士

【摘要】 近年来,海上风电工程发展迅猛,我国目前已经成为全球海上风电累计装机规模最大的国家。其中,单桩基础式风机因受力明确、技术成熟等优点,是目前使用范围最为广泛的基础形式,且逐渐向大型化发展。然而海上风机工作环境恶劣复杂,海上风机时刻需要承受来自海洋环境的风、浪、流等外部侧向荷载,这些荷载都会传递给风机的基础结构,对其结构安全稳定性产生威胁。因此展开对海上风机单桩基础的侧向承载性能分析则显得尤为重要,将直接关乎到整个风电工程的经济性、稳定性与安全性。目前,国内外关于单桩基础的侧向承载力特性分析研究中,主要分为以下三个方法:模型试验法、理论分析法和数值分析法。其中,数值分析法因具有耗时短,成本低,可重复性强等优点得到广泛应用。在国内由叶剑红及其团队开发的FssiCAS数值计算模型,经过多年的发展与完善,在近海工程领域海洋结构物的设计、安全稳定性评价中具有广泛的应用。本文借助数值计算模型FssiCAS为平台,首先开展了一系列对前人现场和室内的试验验证,确保FssiCAS在该方向进行分析研究的准确性和可靠性。然后在此基础上,收集相关工程资料,建立13.6MW海上风机超大直径单桩基础数值模型,再依托FssiCAS数值计算模型,进行海上风机超大直径单桩基础在侧向荷载作用下的承载力特性研究,详细探讨分析了孔隙水、海床土质、加载高度、冲刷以及循环荷载对基础侧向承载力的影响。研究结果如下:(1)通过对前人一系列的现场和室内试验进行模拟验证,且结果均取得了良好的一致性,充分证明通过FssiCAS在海上风机基础侧向承载力分析方向进行数值模拟的稳定性和可靠性。(2)通过对13.6MW海上风机超大直径单桩基础开展在侧向荷载下的承载力特性研究发现海床土体中孔隙水的存在会导致单桩在侧向受载时桩周土体中孔隙水压力的上升积累,土壤的强度和刚度降低,从而导致土体对单桩的支承作用降低,单桩的侧向承载力也因此下降。(3)不同的海床土质也会对单桩的侧向承载力造成影响,当侧向荷载为150MN时,软粘土中的单桩侧向位移为3.75m,而土体强度较大的风化花岗岩沉积土中单桩侧向位移则为1.23m。(4)随着加载高度的不断增大,超大直径单桩基础的侧向极限承载能力也逐渐降低,近似呈抛物线分布。随着冲刷深度的增加,基础的侧向极限承载力是随之递减的,当冲刷深度为0.1D,0.5D和1D时,桩径9m的超大直径单桩的侧向极限承载力相较于无冲刷时分别下降5%,19%和34%。(5)在循环荷载的施加过程中,单桩的荷载-位移曲线呈明显的滞回特性,单桩的侧向峰值位移随循环次数的增加不断累积。随着荷载循环次数的增加,单桩的峰值位移增加变缓,最后趋于一个定值。更多还原

【Abstract】 In recent years,the development of offshore wind power project is rapid,China has now become the world’s largest country in terms of cumulative installed capacity of offshore wind power.Among them,monopile foundation type wind turbine is the most widely used foundation form because of clear force,mature technology and other advantages,and gradually to large-scale development.However,offshore wind turbine working environment is harsh and complex,offshore wind turbine always need to withstand from the marine environment of the wind,waves and currents and other external lateral loads,these loads will be transferred to the wind turbine foundation structure,its structural safety and stability of the threat.Therefore,it is particularly important to analyze the lateral load bearing performance of offshore wind turbine monopile foundation,which is directly related to the economy,stability and safety of the whole wind power project.At present,domestic and foreign research on the analysis of the lateral bearing capacity characteristics of monopile foundation is mainly divided into the following three methods:model test method,theoretical analysis method and numerical analysis method.Among them,the numerical analysis method is widely used because of its advantages of short time-consuming,low cost and high repeatability.The FssiCAS finite element numerical model developed by Ye Jianhong and his team in China has been widely used in the design and safety and stability evaluation of marine structures in offshore engineering field after years of development and improvement.In this thesis,with the help of the numerical computation model FssiCAS as a platform,a series of on-site and indoor experimental validation of the predecessors are first carried out to ensure the accuracy and reliability of the analysis and research carried out by FssiCAS in this direction.Then,on this basis,collect relevant engineering data,establish numerical model of 13.6MW offshore wind turbine large diameter monopile foundation,and then rely on FssiCAS numerical computation model,carry out the research on the bearing capacity characteristics of offshore wind turbine large diameter monopile foundation under the action of lateral load,and discuss and analyze in detail the influence of pore water,seabed soil,loading height,scouring,and cyclic loads on the lateral bearing capacity of the foundation.The results of the study are as follows:(1)Through the simulation verification of a series of field and indoor tests conducted by the former,and the results have achieved good consistency,which fully proves the stability and reliability of numerical simulation in the direction of lateral bearing capacity analysis of offshore wind turbine foundations by FssiCAS.(2)Through the research on the bearing capacity characteristics of 13.6MW offshore wind turbine large-diameter monopile foundation under lateral loading,it is found that the existence of pore water in the seabed soil will lead to the accumulation of pore water pressure in the soil around the pile when the monopile is subjected to lateral loading,and the strength and stiffness of the soil are reduced,which will lead to the reduction of the supporting effect of the soil on the monopile,and the lateral bearing capacity of the monopile will be reduced as a result.(3)Different seabed soils also affect the lateral bearing capacity of monopile,when the lateral load is 150MN,the lateral displacement of monopile in soft clay soil is 3.75m,while the lateral displacement of monopile in weathered granite sedimentary soil,which has larger soil strength,is 1.23m.(4)With the increasing loading height,the lateral ultimate bearing capacity of the oversized diameter monopile foundation also decreases gradually,which is approximately parabolic distribution.With the increase of scour depth,the lateral ultimate bearing capacity of the foundation decreases.When the scour depth is 0.1D,0.5D and 1D,the lateral ultimate bearing capacity of oversized monopile with 9m diameter decreases by 5%,19%and 34%respectively compared with that without scour.(5)In the process of cyclic loading,the load-displacement curves of monopiles show obvious hysteresis characteristics,and the lateral peak displacement of monopiles accumulates with the increase of the number of cycles.With the increase of the number of load cycles,the increase of peak displacement of monopile becomes slower and finally tends to a constant value.更多还原