水平循环荷载下近海软土地基离岸单桩基础模型试验和三维数值分析

发布时间：2018-05-26 18:29

本文选题：单桩基础 + 饱和软土地基　；参考：《西南交通大学》2017年硕士论文

【摘要】：近年来,随着海上风电产业的迅速发展,桩基础(特别是大直径单桩基础)因其结构简单、工期短等优势越来越成为海上风电等海洋工程结构的首选基础形式。同时,由于海洋平台桩基础在其正常服役过程中,将会受到风、波浪、海流等低频循环水平荷载的作用产生累积侧向变形,当桩基础转角位移超过0.5°时,会使得风机机组因基础变形超限无法正常工作。目前,国际上主流研究风电桩基础的非线性分析方法为美国石油协会(API)和挪威船工社所采用的p-y曲线法,而我国现行《港口工程桩基规范》基本上是沿用了美国API规范。但现有的p-y曲线法均基于有限尺寸的桩基试验结果,且试验地基土多为硬黏土和砂土,对于大直径桩基础和饱和软粘土地基难以适用。因此,如何准确有效评估饱和软粘土地基中大直径单桩式风机基础在水平循环荷载作用下的侧向永久累积变形显得尤为重要。为此,本文通过室内缩尺模型试验和有限元数值分析方法研究了饱和软粘土地基中大直径单桩基础在水平低频循环荷载作用下的受力变形特性,主要工作如下:(1)研制了一种新型的水平循环加载装置,原理简单,制造便捷,能够输出不同幅值的低频正弦荷载,可满足室内模型试验的个性化要求。(2)通过室内模型试验研究了单桩基础在水平静载作用下桩身受力和变形特性,利用桩身实测弯矩推算得到桩基水平静力p-y曲线并与规范进行了对比分析。(3)通过室内模型试验研究了单桩基础在水平循环作用下桩身内力及侧向累积变形特性,并分析了不同深度处p-y曲线弱化循环效应。同时也研究分析了桩周土孔隙水压力增长模式,桩周地基土破坏演化模式。(4)基于模型试验结果建立了三维有限元模型,主要研究了单桩基础在循环荷载作用下侧向累积变形以及桩身内力、桩周土抗力和p-y曲线发展情况。同时还分析了循环荷载形式(单向、双向加载)和幅值、桩土界面接触状态对桩基侧向累积变形的影响。
[Abstract]:In recent years, with the rapid development of offshore wind power industry, pile foundation (especially large diameter single pile foundation) has become the preferred foundation for offshore wind power engineering because of its simple structure and short construction period. At the same time, because the pile foundation of offshore platform will be subjected to wind, wave, current and other low-frequency cyclic horizontal loads, the pile foundation will be subjected to accumulated lateral deformation during its normal service. When the displacement of pile foundation angle exceeds 0.5 掳, The fan unit will be unable to work properly due to the deformation of the foundation. At present, the main nonlinear analysis method of wind power pile foundation in the world is the p-y curve method adopted by the American Petroleum Association (API) and the Norwegian Shipbuilding Society, while the current Code of pile Foundation for Port Engineering in China basically follows the API Code of the United States. However, the existing p-y curve method is based on the test results of finite size pile foundation, and the test foundation soil is mostly hard clay and sand soil, so it is difficult to apply to large diameter pile foundation and saturated soft clay foundation. Therefore, how to accurately and effectively evaluate the lateral permanent accumulative deformation of large diameter single pile fan foundation under horizontal cyclic load in saturated soft clay foundation is particularly important. In this paper, the mechanical and deformation characteristics of large diameter single pile foundation in saturated soft clay foundation under horizontal low frequency cyclic loading are studied by scale model test and finite element method. The main work is as follows: (1) A new type of horizontal cyclic loading device has been developed. The principle is simple, the manufacture is convenient, and the low frequency sinusoidal load with different amplitudes can be output. It can meet the individualized requirement of indoor model test. The horizontal static p-y curves of pile foundation are calculated by using the measured bending moment of pile body and compared with the code. The characteristics of pile internal force and lateral cumulative deformation of single pile foundation under horizontal circulation are studied by laboratory model test. The weakening cycle effect of p-y curves at different depths is analyzed. At the same time, the pore water pressure growth model of pile surrounding soil is studied and analyzed. The model of soil failure evolution around pile foundation is analyzed. (4) based on the model test results, a three-dimensional finite element model is established. The lateral cumulative deformation of single pile foundation under cyclic load, the internal force of pile body, the resistance of soil around pile and the development of p-y curve are studied. At the same time, the influence of cyclic load form (unidirectional and bidirectional loading), amplitude and contact state of pile-soil interface on lateral cumulative deformation of pile foundation is also analyzed.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU473.1

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