本文選題：屈曲分析 + 超長(zhǎng)樁�。� 參考：《江蘇大學(xué)》2017年碩士論文

【摘要】：樁基礎(chǔ)因其承載力高、沉降量小等優(yōu)點(diǎn)在深厚軟土地區(qū)廣泛應(yīng)用。近年來,隨著我國(guó)大型基礎(chǔ)設(shè)施建設(shè)的迅猛發(fā)展,在我國(guó)東部沿海深厚軟土地區(qū)超高層建筑、大跨度橋梁以及港口工程中超長(zhǎng)樁、楔形樁等樁基礎(chǔ)的應(yīng)用日益廣泛。軟土地區(qū)超長(zhǎng)樁與普通樁的最大不同之處在于其屈曲穩(wěn)定問題更值得關(guān)注。已有研究表明影響樁屈曲荷載的重要因素不僅有樁側(cè)土彈性抗力,還有樁側(cè)摩阻力和樁身自重,能夠同時(shí)考慮這些因素影響的超長(zhǎng)樁屈曲荷載計(jì)算目前還很少報(bào)道。楔形樁因其承載力大大高于同體積等截面樁而受到越來越多的關(guān)注,從而使設(shè)計(jì)者在樁基礎(chǔ)選型時(shí)有更多選擇。但現(xiàn)有的楔形樁計(jì)算理論大多基于等截面樁展開,其并不能完全體現(xiàn)楔形樁自身特性,這也是楔形樁不能在工程中被廣泛應(yīng)用的原因之一。目前針對(duì)楔形樁自身特性的屈曲穩(wěn)定分析理論研究也相對(duì)較少。基于此,本文應(yīng)用尖點(diǎn)突變理論對(duì)超長(zhǎng)樁和楔形樁屈曲穩(wěn)定性進(jìn)行研究。同時(shí)考慮樁身自重、樁側(cè)摩阻力和樁側(cè)土彈性抗力,通過確定樁-土體系的勢(shì)函數(shù)和分岔集方程,基于尖點(diǎn)突變理論建立樁-土體系的尖點(diǎn)突變模型并導(dǎo)出樁-土體系失穩(wěn)條件,進(jìn)而得到樁基的屈曲臨界荷載。同時(shí)基于能量法原理并應(yīng)用瑞利-里茲法得到樁基的屈曲臨界荷載,從而驗(yàn)證突變理論計(jì)算結(jié)果的可靠性。主要研究?jī)?nèi)容包括以下幾個(gè)方面:1.樁側(cè)土彈性抗力模式是影響樁基屈曲穩(wěn)定的重要因素。鑒于經(jīng)典m法和常數(shù)法在超長(zhǎng)樁、楔形樁等樁基礎(chǔ)屈曲分析中的局限性,考慮樁側(cè)土彈性抗力系數(shù)為更為復(fù)雜的冪數(shù)分布模式,通過Winkle彈性地基梁理論建立樁-土體系總勢(shì)能方程,基于能量法和最小勢(shì)能原理,導(dǎo)出樁身屈曲臨界荷載和樁身穩(wěn)定計(jì)算長(zhǎng)度的計(jì)算公式,并據(jù)此著重分析了樁側(cè)土彈性抗力分布模式對(duì)樁身屈曲穩(wěn)定的影響規(guī)律。2.引入非線性科學(xué)中的尖點(diǎn)突變理論,同時(shí)考慮樁側(cè)土抗力、樁側(cè)摩阻力和樁身自重的影響,根據(jù)樁端約束條件選取樁身撓曲變形函數(shù),通過確定樁-土體系的勢(shì)函數(shù)和分岔集方程,基于尖點(diǎn)突變理論建立樁-土體系的尖點(diǎn)突變模型并導(dǎo)出樁-土體系失穩(wěn)條件,進(jìn)而得到超長(zhǎng)樁的屈曲臨界荷載。同時(shí)基于能量法原理并應(yīng)用瑞利-里茲法計(jì)算超長(zhǎng)樁的屈曲臨界荷載,從而驗(yàn)證突變理論計(jì)算結(jié)果的可靠性。最后著重分析了樁側(cè)土抗力、樁側(cè)摩阻力和樁身自重對(duì)超長(zhǎng)樁屈曲穩(wěn)定的影響。3.在考慮楔形樁樁側(cè)土彈性抗力的基礎(chǔ)上,計(jì)入樁身自重,首先應(yīng)用尖點(diǎn)突變理論對(duì)楔形樁屈曲穩(wěn)定性進(jìn)行分析,給出楔形樁屈曲失穩(wěn)臨界荷載的計(jì)算方法。同時(shí)應(yīng)用能量法進(jìn)一步驗(yàn)證突變理論計(jì)算的屈曲臨界荷載的可靠性。最后著重分析楔形樁的樁身自重和楔形樁樁徑變化對(duì)屈曲臨界荷載的影響。
[Abstract]:Pile foundation is widely used in deep soft soil area because of its high bearing capacity and small settlement. In recent years, with the rapid development of large-scale infrastructure construction in China, the application of super-tall buildings, long-span bridges, super-long piles, wedge-shaped piles and other pile foundations in deep soft soil areas along the eastern coast of China has become increasingly widespread. The biggest difference between super-long pile and ordinary pile in soft soil area is that the buckling stability of pile is more worthy of attention. It has been shown that the important factors affecting pile buckling load are not only the elastic resistance of pile side soil, but also pile friction and pile body weight. The calculation of buckling load of super-long pile which can take account of these factors at the same time is seldom reported at present. Because the bearing capacity of wedge pile is much higher than that of the same volume and equal section pile, more and more attention is paid to it, which makes the designer have more choice in pile foundation selection. However, most of the existing theories of wedge pile are based on the equal section pile, which can not fully reflect the characteristics of the wedge pile itself, which is one of the reasons why the wedge pile can not be widely used in engineering. At present, there are few researches on buckling stability analysis of wedge pile. Based on this, the buckling stability of super-long pile and wedge-shaped pile is studied by using the cusp catastrophe theory. At the same time, considering the weight of the pile body, the friction of the pile side and the elastic resistance of the soil around the pile, the potential function and bifurcation set equation of the pile-soil system are determined. Based on the cusp catastrophe theory, the cusp catastrophe model of pile-soil system is established and the instability condition of pile-soil system is derived, and the critical buckling load of pile foundation is obtained. At the same time, based on the principle of energy method and using Rayleigh-Ritz method, the buckling critical load of pile foundation is obtained, which verifies the reliability of the calculation results of catastrophe theory. The main research contents include the following aspects: 1. The elastic resistance model of pile side soil is an important factor affecting the buckling stability of pile foundation. In view of the limitations of the classical m method and the constant method in the buckling analysis of super-long pile, wedge-shaped pile and other pile foundations, the elastic resistance coefficient of the soil around the pile is considered as a more complex power distribution model. Based on the Winkle elastic foundation beam theory, the total potential energy equation of pile-soil system is established. Based on the energy method and the principle of minimum potential energy, the formulas for calculating the critical buckling load of pile body and the calculating length of pile body stability are derived. Based on this, the influence of elastic resistance distribution mode of pile side soil on the buckling stability of pile body is analyzed emphatically. In this paper, the cusp catastrophe theory of nonlinear science is introduced. Considering the influence of soil resistance, frictional resistance and weight of pile body, the deflection deformation function of pile body is selected according to the constraint condition of pile end. By determining the potential function and bifurcation set equation of pile-soil system, the cusp catastrophe model of pile-soil system is established based on the cusp catastrophe theory, and the instability condition of pile-soil system is derived, and the buckling critical load of super-long pile is obtained. At the same time, based on the principle of energy method and using Rayleigh-Ritz method, the buckling critical load of super-long pile is calculated, which verifies the reliability of the calculation results of catastrophe theory. Finally, the effects of soil resistance, friction and weight on the buckling stability of super-long pile are analyzed. On the basis of considering the elastic resistance of soil on the side of wedge-shaped pile and taking into account the weight of pile body, the buckling stability of wedge-shaped pile is analyzed by using the cusp-point catastrophe theory, and the calculation method of critical buckling load of wedge-shaped pile is given. At the same time, the reliability of the buckling critical load calculated by the catastrophe theory is further verified by the energy method. Finally, the influence of pile weight and diameter variation on buckling critical load of wedge pile is analyzed.
【學(xué)位授予單位】：江蘇大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TU473.1

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