软土地基中柔性桩—土界面接触特性研究

发布时间：2018-06-03 23:33

本文选题：柔性桩 + 接触界面　；参考：《湖南工业大学》2017年硕士论文

【摘要】：柔性桩属于典型的摩擦型桩,摩擦型桩承载能力的大小主要取决于桩侧阻力的发挥,而桩侧阻力的发挥主要取决于桩土接触面的工作性状。本文主要以水泥土桩作为研究对象,以接触力学、摩擦学及胶凝材料学等交叉学科的相关研究成果为基础,采用直剪试验、扫描电镜分析、数值模拟等手段,围绕桩㧟土界面接触特性,对柔性桩㧟土接触面强度影响因素、桩㧟土接触面细观孔隙率影响因素、柔性桩荷载传递影响因素展开探讨。主要研究工作包括,(1)水泥土桩㧟土接触面强度的影响因素研究:采用单变量控制法,对影响桩土接触面强度的部分因素,如界面粗糙度、水泥掺入比、含水率、养护龄期,进行了分析研究。试验结果表明:水泥土㧟土的接触面强度与界面粗糙程度成正相关关系,当粗糙度不超过临界粗糙度时,表现为粗糙度越大,摩擦角越大,而粘聚力随接触面粗糙度值的增大先增大后减小;水泥掺入比的改变对粘聚力的影响较大,且水泥的掺入量并非越大越好,而是存在最佳水泥掺入比(约为0.21);含水率对摩擦角的影响最为明显;粘聚力与摩擦角均随着龄期的增长而有所增长。(2)桩土接触面细观孔隙率的影响因素研究:对扫描电镜常用的三维孔隙率计算方法进行了分析,对其计算方法的利弊与适用范围进行了论证,并提出了改进的三维孔隙率计算模型;基于大量试验数据,采用MATLAB软件实现计算,试验结果证明了改进计算模型的合理性;对水泥土㧟土接触面进行了扫描电镜试验,并通过对其孔隙率的计算,分析了水泥掺入比、含水率等因素对接触面孔隙率的影响;从水化反应产物的联结状态出发,对接触面强度的增长原因进行了分析。(3)水泥土桩荷载传递的影响因素分析:建立了考虑楔角的荷载传递关系表达式,建立了数值计算模型,分析了桩㧟土相对刚度、楔形桩的楔角、桩长等因素,对柔性桩荷载传递规律的影响,对比试验结果表明:桩㧟土相对刚度对桩的荷载传递的影响是相对的,主要取决于地基破坏的形式;楔形桩的楔角对桩侧阻力的发挥具有决定作用,楔角越大,越有利于桩侧阻力的发挥;在理想均质土层中,桩侧阻力分布形式只与楔角有关,而桩顶荷载大小无关;所有桩型都存在桩端阻力强化效应。
[Abstract]:Flexible pile is a typical friction pile. The bearing capacity of friction pile mainly depends on the exertion of pile side resistance, while the exertion of pile side resistance mainly depends on the working characteristics of pile-soil interface. In this paper, the cement soil pile as the research object, based on the contact mechanics, tribology and cementing materials and other cross-disciplinary research results, using direct shear test, scanning electron microscope analysis, numerical simulation and other means, around the pile? Soil interface contact characteristics for flexible piles? Influence factors of soil contact strength, pile? The influence factors of soil contact surface meso porosity and flexible pile load transfer are discussed. The main research work includes 1) cement soil pile? Study on influencing factors of soil contact strength: single variable control method is used to analyze some factors affecting the strength of pile-soil interface, such as interface roughness, cement blending ratio, moisture content and curing age. The test results show that: cement soil? There is a positive correlation between the contact surface strength and the roughness of interface. When the roughness is less than the critical roughness, the larger the roughness is, the greater the friction angle is, while the cohesion force increases first and then decreases with the increase of the roughness value of the interface. The change of cement blending ratio has a great influence on the cohesion, and the content of cement is not as much as possible, but there is the best cement blending ratio (about 0.21%), the effect of moisture content on friction angle is the most obvious. The factors influencing the meso-porosity of pile-soil contact surface are studied. The three dimensional porosity calculation method commonly used in scanning electron microscope is analyzed. The advantages and disadvantages of the calculation method and the applicable range are demonstrated, and an improved three-dimensional porosity calculation model is put forward, and based on a large number of experimental data, the calculation is realized by using MATLAB software, and the experimental results prove the rationality of the improved calculation model. Cement? The influence of cement ratio, water content and other factors on the porosity of soil contact surface was analyzed by SEM test and the calculation of porosity of soil contact surface, starting from the connection state of hydration reaction products, the influence of cement ratio and water content on the porosity of contact surface was analyzed. The influence factors of load transfer of cement soil pile are analyzed: the expression of load transfer relation considering wedge angle is established, the numerical calculation model is established, and the pile is analyzed. The influence of relative stiffness of soil, wedge angle of wedge pile, length of pile and other factors on the load transfer law of flexible pile shows that: pile? The influence of soil relative stiffness on the load transfer of pile is relative, mainly depends on the failure form of foundation, the wedge angle of wedge pile plays a decisive role on the exertion of pile side resistance, the bigger the wedge angle is, the more favorable it is to the exertion of pile side resistance. In the ideal homogeneous soil layer, the distribution of pile side resistance is only related to the wedge angle, but the pile top load is independent, and all pile types have the effect of pile tip resistance strengthening.
【学位授予单位】：湖南工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU473.1

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