本文選題：大直徑 + 樁　； 參考：《浙江大學(xué)》2013年碩士論文

【摘要】：近年來,隨著近海工程的發(fā)展,特別是近海風(fēng)電產(chǎn)業(yè)的迅速崛起,樁基礎(chǔ)呈現(xiàn)出直徑不斷增大的發(fā)展趨勢(shì)。國(guó)內(nèi)外常見的近海風(fēng)電機(jī)組樁基型式包括超大直徑單樁基礎(chǔ)、三腳架基礎(chǔ)、導(dǎo)管架基礎(chǔ)和群樁基礎(chǔ)等。其中超大直徑單樁基礎(chǔ)(monopile)直徑可達(dá)3-8m,即使其它風(fēng)機(jī)群(多)樁基礎(chǔ)的基樁直徑也達(dá)1.5-2.5m。 目前,p-y曲線法被公認(rèn)為樁基水平非線性變形的最有效分析方法,并被美國(guó)石油協(xié)會(huì)(API)所采用。我國(guó)現(xiàn)行《港口工程樁基規(guī)范》(JTJ254-98)雖建議了樁基p-y曲線分析法,但基本上是對(duì)API規(guī)范的沿用。然而現(xiàn)有樁基p-y曲線均基于有限尺寸樁基的試驗(yàn)結(jié)果,對(duì)于大直徑樁基難以適用。因此開展大直徑樁水平受荷特性的研究具有重要的理論意義和實(shí)際指導(dǎo)意義。 本文通過離心模型試驗(yàn)研究了砂性土中大直徑單樁分別在水平靜力和循環(huán)荷載作用下的受力和變形特性。驗(yàn)證了通過實(shí)測(cè)樁身彎矩推算樁身變形和樁周土反力的有效性,分別獲得了干砂和飽和砂的大直徑單樁水平靜力p-y曲線。在修正p-y曲線初始剛度的基礎(chǔ)上,提出了用雙曲線型p-y曲線來分析水平受荷大直徑單樁的內(nèi)力和變形。通過開展循環(huán)加載試驗(yàn),揭示了水平單向循環(huán)荷載下大直徑單樁的樁身變形及內(nèi)力變化特性,試驗(yàn)結(jié)果顯示樁身變形、最大彎矩及卸載剛度近似與循環(huán)次數(shù)的對(duì)數(shù)線性相關(guān)。最后,由各循環(huán)次數(shù)下的樁身彎矩獲得了大直徑單樁水平循環(huán)p-y曲線,提出了循環(huán)應(yīng)力比相關(guān)的p-y曲線循環(huán)弱化因子,以及相應(yīng)的樁基變形累積和內(nèi)力變化分析方法。 進(jìn)一步,基于室內(nèi)三軸固結(jié)排水剪切試驗(yàn)等獲得剪脹性砂土的物理力學(xué)特性參數(shù),利用大型通用有限元軟件ABAQUS,開展了近海大直徑單樁基礎(chǔ)在水平荷載作用下的三維有限元數(shù)值分析,揭示了加載過程中樁周土的應(yīng)力路徑,探討了樁周土內(nèi)摩擦角、剪脹角及樁土接觸面特性等對(duì)三維數(shù)值分析模型計(jì)算結(jié)果的影響,并得到了離心模型試驗(yàn)的驗(yàn)證,進(jìn)而提出了砂土海床中大直徑單樁基礎(chǔ)的合理數(shù)值分析模型及參數(shù)取值方法。最后,利用該數(shù)值分析模型分析了現(xiàn)有樁基承載力和變形分析方法對(duì)超大直徑單樁的有效性,并提出了該型式樁基臨界埋深的確定方法。
[Abstract]:In recent years, with the development of offshore engineering, especially the rapid rise of offshore wind power industry, pile foundation presents a trend of increasing diameter. The common types of offshore wind turbine pile foundation at home and abroad include super-large diameter single pile foundation, tripod foundation, jacket foundation and pile group foundation. The diameter of single pile foundation with super-large diameter can reach 3-8 m, and the diameter of foundation pile of other fan group (multi-pile foundation) is 1.5-2.5 m. At present the p-y curve method is recognized as the most effective analytical method for the horizontal nonlinear deformation of pile foundation and used by the American Petroleum Association (API). JTJ254-98) although the p-y curve analysis method of pile foundation is suggested, the API specification is adopted basically. However, the existing p-y curves of pile foundation are based on the test results of finite size pile foundation, so it is difficult to apply to large diameter pile foundation. Therefore, it is of great theoretical and practical significance to study the horizontal loading characteristics of large diameter piles. In this paper, the stress and deformation characteristics of large diameter single pile in sandy soil under horizontal static load and cyclic load are studied by centrifugal model test. The validity of calculating the deformation of pile body and the reaction force of soil around pile is verified by the measured bending moment of pile body. The horizontal static p-y curves of large diameter single pile with dry sand and saturated sand are obtained respectively. On the basis of modifying the initial stiffness of p-y curve, a hyperbolic p-y curve is proposed to analyze the internal force and deformation of a single pile with large diameter under horizontal loading. By carrying out cyclic loading tests, the deformation and internal force of large diameter single pile under horizontal unidirectional cyclic loading are revealed. The experimental results show that the deformation, maximum bending moment and unloading stiffness of pile are approximately related to the logarithmic logarithm of cycle number. Finally, the horizontal cyclic p-y curve of large diameter single pile is obtained from the bending moment of pile body under various cycles, and the cyclic weakening factor of the p-y curve is proposed, and the corresponding analytical method of pile foundation deformation accumulation and internal force change is presented. Furthermore, the physical and mechanical properties of the dilatant sand are obtained based on the laboratory triaxial consolidation and drainage shear tests. The 3-D finite element numerical analysis of offshore large diameter single pile foundation under horizontal load is carried out by using Abaqus, the stress path of soil around pile during loading is revealed, and the internal friction angle of soil around pile is discussed. The influence of shear expansion angle and pile-soil interface characteristics on the calculation results of 3D numerical analysis model has been obtained. The centrifugal model test has been verified, and a reasonable numerical analysis model and parameter selection method for single pile foundation with large diameter in sand seabed have been put forward. Finally, the validity of existing pile foundation bearing capacity and deformation analysis methods for super-large diameter single pile is analyzed by using the numerical analysis model, and a method for determining the critical buried depth of this type of pile foundation is put forward.
【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2013
【分類號(hào)】：TU473.1

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