考虑桩—岩相互作用的红层泥岩桩基承载力计算方法研究
发布时间：2018-08-28 07:58
【摘要】：桩基承载力的核心问题是桩-土相互作用问题,然而,现阶段,对于泥岩与结构接触面剪切特性的研究极少,已有的粗粒土、砂土等土质与桩相互作用机理又不适于拿来用于红层泥岩地层。而泥皮是影响桩-岩相互作用的重要因素,泥皮夹在钻孔灌注桩与桩侧土层之间,形成一薄弱夹层,由于其压缩性高、抗剪强度低等特点,常常是导致桩侧摩阻力降低的主要因素。为解决这一实际工程问题,论文拟从桩-岩相互作用机理出发,结合室内土工参数试验、桩-岩接触面直剪试验,得到红层泥岩桩侧泥皮土物理力学参数和桩-岩接触面剪切特性及其本构,然后采用有限差分软件建立正常桩和含泥皮桩基数值模型,研究泥皮效应对红层泥岩桩基承载性状的影响,并对含泥皮红层泥岩桩基承载力公式进行修正。具体包括以下几个方面研究内容：(1)通过采集红层泥岩试样与制作混凝土试块,进行室内大型桩-岩接触面剪切试验,对试验结果进行分析得到桩-岩接触面剪切破坏特性,并根据接触面剪切试验结果,建立红层泥岩桩-岩接触面本构模型,并推导出其本构方程：(2)通过分析泥皮形成机理,对红层泥岩桩侧泥皮土进行取样并进行室内土工参数试验,得到红层泥岩桩侧泥皮土物理力学参数,主要为后续建模提供泥皮参数。调研现有文献并统计其它地层及泥皮土的物理力学参数,分析泥皮土性状与原状土的差异。(3)利用FLAC3D有限差分软件,建立考虑岩桩-岩接触面本构的红层泥岩单桩静载试验模型,首先,分析不同桩长情况下,正常桩基与含泥皮桩基承载特性；然后对含泥皮桩基静载试验进行参数敏感性分析,主要研究了泥皮厚度、泥皮弹性模量、泥皮粘聚力、泥皮内摩擦角等因素对含泥皮红层泥岩桩基承载性状的影响。(4)通过数值模拟分析结果,分析了泥皮各因素变化对桩基承载性状的影响,提出泥皮厚度桩基侧摩阻力修正系数,对规范桩基承载力计算公式进行修正：目前,随着桩基工程的大规模开展,关于泥皮缺陷桩承载性状的问题越来越受到重视,本论文研究成果对实际桩基工程中的含泥皮红层泥岩桩基设计有一定的参考价值。
[Abstract]:The core problem of pile bearing capacity is pile-soil interaction. However, at present, there are few researches on shear characteristics of mudstone and structural interface. The interaction mechanism of sand and pile is not suitable for red mudstone formation. The mud crust is an important factor affecting the pile-rock interaction. The mud jacket between the bored pile and the pile side soil layer forms a weak interlayer, because of its high compressibility and low shear strength. It is often the main factor that leads to the reduction of pile side friction. In order to solve this practical engineering problem, the paper intends to proceed from the pile-rock interaction mechanism, combined with the indoor geotechnical parameter test, and the direct shear test of pile-rock interface. The physical and mechanical parameters of the mudstone pile side and the shear characteristics of the pile-rock interface and its constitutive structure are obtained, and then the numerical models of the normal pile and the mud-covered pile foundation are established by using the finite difference software. The influence of mud-skin effect on the bearing capacity of red mudstone pile foundation is studied, and the formula of bearing capacity of red mudstone pile foundation with mud-bearing crust is modified. The specific research contents are as follows: (1) through collecting red layer mudstone samples and making concrete test blocks, the shear test of large pile-rock interface is carried out, and the shear failure characteristics of pile-rock contact surface are obtained by analyzing the test results. Based on the shear test results of the contact surface, the constitutive model of the red mudstone pile-rock interface is established, and its constitutive equation is derived: (2) by analyzing the mechanism of mud crust formation, The physical and mechanical parameters of the red mudstone pile side mud soil were obtained by sampling the red mudstone pile side mud soil and carrying out the laboratory geotechnical parameter test, which mainly provided the mud crust parameter for the subsequent modeling. The physical and mechanical parameters of other strata and muddy soil are investigated and the differences between the characteristics of muddy soil and undisturbed soil are analyzed. (3) the static load test model of single red mudstone pile considering the constitutive structure of rock pile-rock interface is established by using FLAC3D finite difference software. Firstly, the load-bearing characteristics of normal pile foundation and mud-covered pile foundation are analyzed under different pile lengths, and then the parameter sensitivity analysis of the static load test of mud-covered pile foundation is carried out, which mainly studies the thickness of mud skin, the elastic modulus of mud skin, and the cohesion of mud skin. The influence of factors such as internal friction angle of mud crust on bearing behavior of mudstone pile foundation with mud skin red layer is discussed. (4) through numerical simulation results, the influence of various factors of mud skin on bearing behavior of pile foundation is analyzed, and the modified coefficient of side friction resistance of pile foundation with mud skin thickness is put forward. The formula for calculating the bearing capacity of pile foundation is revised. At present, with the large-scale development of pile foundation engineering, more and more attention has been paid to the bearing behavior of defective pile with mud and skin. The research results of this paper have certain reference value for the design of mudstone pile foundation with mud skin red bed in actual pile foundation engineering.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TU473.1
本文编号：2208773
[Abstract]:The core problem of pile bearing capacity is pile-soil interaction. However, at present, there are few researches on shear characteristics of mudstone and structural interface. The interaction mechanism of sand and pile is not suitable for red mudstone formation. The mud crust is an important factor affecting the pile-rock interaction. The mud jacket between the bored pile and the pile side soil layer forms a weak interlayer, because of its high compressibility and low shear strength. It is often the main factor that leads to the reduction of pile side friction. In order to solve this practical engineering problem, the paper intends to proceed from the pile-rock interaction mechanism, combined with the indoor geotechnical parameter test, and the direct shear test of pile-rock interface. The physical and mechanical parameters of the mudstone pile side and the shear characteristics of the pile-rock interface and its constitutive structure are obtained, and then the numerical models of the normal pile and the mud-covered pile foundation are established by using the finite difference software. The influence of mud-skin effect on the bearing capacity of red mudstone pile foundation is studied, and the formula of bearing capacity of red mudstone pile foundation with mud-bearing crust is modified. The specific research contents are as follows: (1) through collecting red layer mudstone samples and making concrete test blocks, the shear test of large pile-rock interface is carried out, and the shear failure characteristics of pile-rock contact surface are obtained by analyzing the test results. Based on the shear test results of the contact surface, the constitutive model of the red mudstone pile-rock interface is established, and its constitutive equation is derived: (2) by analyzing the mechanism of mud crust formation, The physical and mechanical parameters of the red mudstone pile side mud soil were obtained by sampling the red mudstone pile side mud soil and carrying out the laboratory geotechnical parameter test, which mainly provided the mud crust parameter for the subsequent modeling. The physical and mechanical parameters of other strata and muddy soil are investigated and the differences between the characteristics of muddy soil and undisturbed soil are analyzed. (3) the static load test model of single red mudstone pile considering the constitutive structure of rock pile-rock interface is established by using FLAC3D finite difference software. Firstly, the load-bearing characteristics of normal pile foundation and mud-covered pile foundation are analyzed under different pile lengths, and then the parameter sensitivity analysis of the static load test of mud-covered pile foundation is carried out, which mainly studies the thickness of mud skin, the elastic modulus of mud skin, and the cohesion of mud skin. The influence of factors such as internal friction angle of mud crust on bearing behavior of mudstone pile foundation with mud skin red layer is discussed. (4) through numerical simulation results, the influence of various factors of mud skin on bearing behavior of pile foundation is analyzed, and the modified coefficient of side friction resistance of pile foundation with mud skin thickness is put forward. The formula for calculating the bearing capacity of pile foundation is revised. At present, with the large-scale development of pile foundation engineering, more and more attention has been paid to the bearing behavior of defective pile with mud and skin. The research results of this paper have certain reference value for the design of mudstone pile foundation with mud skin red bed in actual pile foundation engineering.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TU473.1
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