【摘要】：樁基礎(chǔ)承載力通常由側(cè)摩阻力與樁端承載力組成。對于樁體側(cè)摩阻力的大小，目前多假定其與法向應(yīng)力呈線性比例關(guān)系，但對于土體與混凝土樁體剪切過程中的土體的應(yīng)力應(yīng)變傳遞規(guī)律研究較少。樁-土接觸面的剪切性質(zhì)與剪切過程中土顆粒的運(yùn)動(dòng)形式緊密相關(guān)，為討論土體與混凝土接觸面剪切性質(zhì)，本文結(jié)合肇源松花江特大橋工程實(shí)例，采用室內(nèi)試驗(yàn)結(jié)合數(shù)值模擬的方法，研究了土體與混凝土的剪切特性，為進(jìn)一步理解土體與混凝土剪應(yīng)力的發(fā)揮機(jī)理提供了一定參考。 首先，選取該工程中土體與混凝土試樣，進(jìn)行了土體與混凝土的接觸面中型剪切試驗(yàn)，其中試驗(yàn)土樣包括粘性土、細(xì)砂、粗砂，法向荷載根據(jù)實(shí)際工程確定。中型剪切試驗(yàn)結(jié)果顯示，樁-土接觸面的峰值剪切強(qiáng)度與法向應(yīng)力呈較好的線性關(guān)系，對于粘性土，剪切過程中還表現(xiàn)出一定的粘聚力特征。因此，完全可以借鑒土體中庫侖-摩爾理論描述接觸面的剪切強(qiáng)度。在試驗(yàn)過程中無法從土樣中提取足夠多土體應(yīng)力應(yīng)變信息，故考慮采用數(shù)值模擬的方法反演中型剪切試驗(yàn)過程，研究土體剪應(yīng)力在剪切過程中的傳遞規(guī)律。 顆粒流方法被引入剪切試驗(yàn)的數(shù)值模擬研究中，以研究砂土與混凝土的剪切破壞特征。顆粒流作為一種離散元方法，很好反映了砂土顆粒之間的法向、切向、滑動(dòng)作用，從顆粒之間的相關(guān)作用為出發(fā)點(diǎn)構(gòu)建本構(gòu)方程，具有其他方法不具備的諸多優(yōu)點(diǎn)。 在顆粒流模型建立的過程中，顆粒之間的細(xì)觀參數(shù)決定了模型的宏觀性質(zhì)。為了準(zhǔn)確獲得模型顆粒細(xì)觀參數(shù)，第四章中采用正交試驗(yàn)的方法，基于砂土的三軸試驗(yàn)，研究了孔隙率、摩擦系數(shù)、法向剛度、切向-法向剛度比等四項(xiàng)細(xì)觀參數(shù)對三軸試驗(yàn)中砂土內(nèi)摩擦角、泊松比、彈性模量的影響規(guī)律。結(jié)果顯示：砂土的內(nèi)摩擦角通常與顆粒的摩擦系數(shù)、切向-法向剛度比有關(guān)；砂土的彈性模量通常與顆粒的法向剛度、切向-法向剛度比有關(guān)；砂土的泊松比主要由顆粒的切向-法向剛度比、孔隙率決定。 而后，在確定了顆粒細(xì)觀參數(shù)的基礎(chǔ)上，建立了砂土與混凝土中型剪切試驗(yàn)的顆粒流模型，進(jìn)行了不同法向荷載下砂土的剪切試驗(yàn)。數(shù)值模擬結(jié)果與中型剪切試驗(yàn)結(jié)果達(dá)到了較好的吻合，再次證明了離散元方法在砂土性質(zhì)模擬中的合理性。通過對比土體顆粒的應(yīng)力、位移、孔隙率等分布特征，總結(jié)了土體與混凝土剪切過程中顆粒位移與應(yīng)力的傳遞規(guī)律。同時(shí)，采用支持矢量機(jī)的方法，準(zhǔn)確劃分了土體中剪切帶的范圍，討論了法向應(yīng)力、顆粒尺寸對剪切帶最大厚度的影響，結(jié)果顯示：顆粒尺寸越大，，法向應(yīng)力越小，則土體中剪切帶厚度越大。 本研究結(jié)果對于深入認(rèn)識(shí)土體與混凝土結(jié)構(gòu)體之間的剪切破壞機(jī)理以及了解土體中剪切帶的相關(guān)性質(zhì)具有促進(jìn)作用。
[Abstract]:The bearing capacity of pile foundation is usually composed of side friction resistance and pile end bearing capacity. At present, it is assumed that the frictional resistance of pile is linear proportional to normal stress, but there is little research on the law of stress and strain transfer between soil and concrete pile in shear process. The shear properties of pile-soil interface are closely related to the movement of soil particles during shear. In order to discuss the shear properties of soil and concrete interface, this paper combines with the example of Zhaoyuan Songhua River Bridge. The shear characteristics of soil and concrete are studied by the method of laboratory test and numerical simulation, which provides a certain reference for further understanding the mechanism of shear stress between soil and concrete. First of all, the medium shear test of the interface between soil and concrete is carried out by selecting the soil and concrete samples in this project. The test soil samples include cohesive soil, fine sand, coarse sand, and the normal load is determined according to the actual engineering. The results of medium shear test show that the peak shear strength of the pile-soil interface is linear with the normal stress, and the cohesive force is also shown in the shear process of the clay. Therefore, the shear strength of the contact surface can be described by using the Kulun-Moore theory in soil. Enough information of soil stress and strain can not be extracted from the soil sample during the test, so the numerical simulation method is considered to invert the medium shear test process and to study the law of soil shear stress transfer in the shear process. The particle flow method is introduced into the numerical simulation of shear tests to study the shear failure characteristics of sand and concrete. Particle flow, as a discrete element method, well reflects the normal, tangential and sliding effects of sand particles. The constitutive equation is constructed from the point of view of the correlation between particles, which has many advantages that other methods do not have. In the process of establishing the particle flow model, the macroscopic properties of the model are determined by the meso-parameters between particles. In the fourth chapter, the porosity, friction coefficient and normal stiffness of sand were studied by orthogonal test based on triaxial test of sand. The influence of four mesoscopic parameters, such as tangential to normal stiffness ratio, on the internal friction angle, Poisson's ratio and elastic modulus of sand in triaxial test. The results show that the internal friction angle of sand is usually related to the friction coefficient of particles and the tangential to normal stiffness ratio, and the elastic modulus of sand is usually related to the normal stiffness and tangential normal stiffness ratio of sand. The Poisson's ratio of sand is mainly determined by the tangential-normal stiffness ratio and porosity. Then, on the basis of the determination of the particle meso parameters, the particle flow model of medium shear tests of sand and concrete is established, and the shear tests of sand under different normal loads are carried out. The results of numerical simulation are in good agreement with the results of medium shear test, and the rationality of the discrete element method in the simulation of sand properties is proved again. By comparing the distribution characteristics of soil particle stress, displacement and porosity, the transfer law of particle displacement and stress in the shear process between soil and concrete is summarized. At the same time, by using support vector machine, the range of shear band in soil is accurately divided, and the normal stress and the effect of particle size on the maximum thickness of shear band are discussed. The results show that the larger the particle size, the smaller the normal stress. The thickness of shear band in soil is larger. The results of this study can promote the understanding of shear failure mechanism between soil and concrete structure and the properties of shear band in soil.
【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TU473.1

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