近海风机地基土力学响应基本规律的试验研究及数值分析

发布时间：2018-07-29 06:06

【摘要】：海上风电工程对其自身结构、基础和地基土的变形控制要求极其严格，然而目前对海上风电基础与地基土相互作用规律以及地基土变形响应规律的认识仍显十分有限。本文在试验设备研制的基础上，着重通过系列试验及有限元和离散元数值模拟，对近海风机单桩基础附近地基土的特有应力变化和应变响应等复杂力学行为、规律和机理展开研究，取得以下主要的新成果：（1）成功研制了一台可实现多类型复杂加载的大型智能控制压扭多轴加载试验机，形成了一个集动静加载压扭、真三轴、平面应变和常规三轴为一体的多功能土动力试验平台，被用于模拟海上风机基础附近地基土中发生的应力主轴往返循环旋转作用等复杂力学行为。（2）采用两种不同本构模型的三维有限元计算分析，阐明了海上风浪荷载作用环境下风机单桩基础附近地基土中应力变化的特性规律及主要影响因素。表明桩基础附近地基土中存在着极其复杂的应力状态及变化，尤其是基础附近的表层地基土中的主应力方向在三维空间内发生有限角度往返循环旋转现象；当风、浪方向一致或二者夹角很小时，退化为二维平面内的应力主轴有限角度往返循环旋转；数值分析中采用的土本构模型的不同对上述的应力变化规律性影响不大。（3）通过纯应力主轴有限角度往返循环旋转系列试验及离散元模拟分析，揭示了二维平面内的有限角度应力主轴往返循环旋转作用下饱和砂土应变响应的特有规律及细观机理，，发现：a）各个方向的应变分量的发展趋势受到应力主轴往返旋转角度幅值α和初始主应力方向角α0的明显影响，随着循环周次的增加呈现出应变硬化效应；b）体应变出现先缩后胀的规律性变化且受α的显著影响，该体胀是由二维平面内砂土颗粒发生往返旋转错动过程中在与其垂直的中主应力作用方向上发生侧胀引起的；c）剪应力-剪应变关系和应变路径受到α和α0的共同影响，双幅剪应变值与以往的应力主轴单向连续旋转作用情形相比要小；d）剪应变增量的方向仅随总剪应力（起始剪应力和循环剪应力之和）的加卸变化而变化，与应力主轴单向连续旋转作用情形有显著差异；e）粒状颗粒运动以滑移变形为主，颗粒偏转和试样各向异性程度的发展都不明显。
[Abstract]:Offshore wind power engineering has very strict requirements for its own structure, foundation and foundation soil deformation control. However, at present, the understanding of the interaction law between offshore wind power foundation and foundation soil and the law of foundation soil deformation response is still very limited. On the basis of the development of the test equipment, the complex mechanical behaviors such as the special stress variation and strain response of the foundation soil near the single pile foundation of offshore fan are studied by means of a series of tests, finite element and discrete element numerical simulation. The main results are as follows: (1) A large intelligent control multi-axis load testing machine is developed, which can realize multi-type complex loading, and a set of static and static loading compression and torsion is formed. A multifunctional soil dynamic test platform with true triaxial, plane strain and conventional triaxial, It is used to simulate complex mechanical behaviors such as cyclic rotation of stress spindle in foundation soil near the foundation of offshore fan. (2) Three-dimensional finite element analysis of two different constitutive models is used. The characteristics and main influencing factors of stress variation in foundation soil near single pile foundation of fan under wind and wave loads are expounded. It shows that there are very complex stress states and changes in the foundation soil near the pile foundation, especially in the surface soil near the foundation, the direction of the principal stress in the surface soil is rotated at a finite angle in three dimensional space, when the wind, The wave direction is the same or the angle between them is very small, which degenerates to the finite angle of the stress spindle in the two-dimensional plane and circulates back and forth. The difference of soil constitutive models used in numerical analysis has little effect on the regularity of stress change mentioned above. (3) A series of tests and discrete element simulation analysis of circular rotation with finite angle of pure stress spindle are carried out. The special law and the mesoscopic mechanism of the strain response of saturated sand under the cyclic rotation of the finite angle stress spindle in two-dimensional plane are revealed. It is found that the development trend of strain components in each direction is obviously influenced by the rotation angle amplitude 伪 and the initial principal stress direction angle 伪 0 of the stress spindle, and the strain hardening effect appears with the increase of cycle cycles. B) the regular change of body strain is first shrinkage and then dilatation, which is caused by lateral dilatation of sand particles in the direction of vertical principal stress in the process of rotation and dislocation of sand particles in two-dimensional plane. C) the shear stress-shear strain relationship and strain path are affected by 伪 and 伪 _ 0, and the two-amplitude shear strain is smaller than that of the stress spindle under unidirectional and continuous rotation. D) the direction of shear strain increment only varies with the total shear stress (the sum of initial shear stress and cyclic shear stress), which is significantly different from that of the stress spindle in the case of unidirectional continuous rotation. The development of particle deflection and anisotropy is not obvious.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU476

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