【摘要】：海上風(fēng)電工程對其自身結(jié)構(gòu)、基礎(chǔ)和地基土的變形控制要求極其嚴(yán)格，然而目前對海上風(fēng)電基礎(chǔ)與地基土相互作用規(guī)律以及地基土變形響應(yīng)規(guī)律的認(rèn)識仍顯十分有限。本文在試驗設(shè)備研制的基礎(chǔ)上，著重通過系列試驗及有限元和離散元數(shù)值模擬，對近海風(fēng)機單樁基礎(chǔ)附近地基土的特有應(yīng)力變化和應(yīng)變響應(yīng)等復(fù)雜力學(xué)行為、規(guī)律和機理展開研究，取得以下主要的新成果： （1）成功研制了一臺可實現(xiàn)多類型復(fù)雜加載的大型智能控制壓扭多軸加載試驗機，形成了一個集動靜加載壓扭、真三軸、平面應(yīng)變和常規(guī)三軸為一體的多功能土動力試驗平臺，被用于模擬海上風(fēng)機基礎(chǔ)附近地基土中發(fā)生的應(yīng)力主軸往返循環(huán)旋轉(zhuǎn)作用等復(fù)雜力學(xué)行為。 （2）采用兩種不同本構(gòu)模型的三維有限元計算分析，闡明了海上風(fēng)浪荷載作用環(huán)境下風(fēng)機單樁基礎(chǔ)附近地基土中應(yīng)力變化的特性規(guī)律及主要影響因素。表明樁基礎(chǔ)附近地基土中存在著極其復(fù)雜的應(yīng)力狀態(tài)及變化，尤其是基礎(chǔ)附近的表層地基土中的主應(yīng)力方向在三維空間內(nèi)發(fā)生有限角度往返循環(huán)旋轉(zhuǎn)現(xiàn)象；當(dāng)風(fēng)、浪方向一致或二者夾角很小時，退化為二維平面內(nèi)的應(yīng)力主軸有限角度往返循環(huán)旋轉(zhuǎn)；數(shù)值分析中采用的土本構(gòu)模型的不同對上述的應(yīng)力變化規(guī)律性影響不大。 （3）通過純應(yīng)力主軸有限角度往返循環(huán)旋轉(zhuǎn)系列試驗及離散元模擬分析，揭示了二維平面內(nèi)的有限角度應(yīng)力主軸往返循環(huán)旋轉(zhuǎn)作用下飽和砂土應(yīng)變響應(yīng)的特有規(guī)律及細(xì)觀機理，，發(fā)現(xiàn)：a）各個方向的應(yīng)變分量的發(fā)展趨勢受到應(yīng)力主軸往返旋轉(zhuǎn)角度幅值α和初始主應(yīng)力方向角α0的明顯影響，隨著循環(huán)周次的增加呈現(xiàn)出應(yīng)變硬化效應(yīng)；b）體應(yīng)變出現(xiàn)先縮后脹的規(guī)律性變化且受α的顯著影響，該體脹是由二維平面內(nèi)砂土顆粒發(fā)生往返旋轉(zhuǎn)錯動過程中在與其垂直的中主應(yīng)力作用方向上發(fā)生側(cè)脹引起的；c）剪應(yīng)力-剪應(yīng)變關(guān)系和應(yīng)變路徑受到α和α0的共同影響，雙幅剪應(yīng)變值與以往的應(yīng)力主軸單向連續(xù)旋轉(zhuǎn)作用情形相比要小；d）剪應(yīng)變增量的方向僅隨總剪應(yīng)力（起始剪應(yīng)力和循環(huán)剪應(yīng)力之和）的加卸變化而變化，與應(yīng)力主軸單向連續(xù)旋轉(zhuǎn)作用情形有顯著差異；e）粒狀顆粒運動以滑移變形為主，顆粒偏轉(zhuǎn)和試樣各向異性程度的發(fā)展都不明顯。
[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 偽 and the initial principal stress direction angle 偽 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 偽 and 偽 _ 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.
【學(xué)位授予單位】：清華大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2014
【分類號】：TU476

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