基于物理性质的土体强度和变形特性研究
发布时间：2019-06-29 12:58
【摘要】：我国东南沿海和部分内陆沿江城市(如武汉、昆明等)广泛存在软弱黏土,而且工程量巨大。虽然现有土力学理论对工程实践有一定的指导作用,但事实表明效果有限。大部分关于土的强度和变形的理论是以连续介质为对象的研究成果,应用到像土这样的非连续、结构性强的介质中,没有达到真正解决实际工程问题的目的,如：现有的土体本构模型大多没有充分考虑土的物理特性,模型参数取值不确定性太大,造成应力、应变的计算结果波动过大,在工程应用中存在明显缺陷。为此,本文基于土非连续介质和结构性强的特点,采用现代测试新技术(弯曲元剪切波速测试),通过土体细观结构分析试验与宏观力学特性试验相结合来探索描述土体结构新方法,建立土的应力状态方程,提出土体新的强度准则,创立新的结构性土体压缩特性预测方法,建立土的物理力学本构模型。并通过数值分析研究,应用新的理论成果解决实际工程问题。本文对阐明非连续性土体的应力状态、强度和变形规律具有重要理论意义和工程应用价值。 主要研究内容和成果如下： 1、根据土体的非连续特性,引入孔隙率这一物性指标,建立土体的应力状态方程,通过对比分析指出现有强度理论(如莫尔-库伦理论)的不足。在对正常固结粘土强度特性简单的机理分析基础上,通过一系列常规三轴固结压缩试验,分析了不同初始孔隙比和塑性指数对其力学性质的影响。提出一个新的物性参数ω,该参数能够综合反映出正常固结饱和粘土的矿物含量及所处状态,建立了粘土抗剪强度指标与ω之间的关系,进而考虑对莫尔-库伦准则进行修正。 2、基于Liu和Carter的结构性破损压缩模型,提出了一个简化的物性变化参数：孔隙相对变化指数Ev,考虑初始孔隙变化对土体压缩性状的影响,通过对杭州原状软土进行不同初始振动的固结试验,分别建立了孔隙相对变化指数Ev与土体结构屈服应力σy及结构破损指数b的相关关系,据此提出了新的利用室内压缩试验结果预测原位压缩曲线的方法。 3、探讨了蛋形屈服函数参数的确定方法,建立了蛋形屈服函数参数a、b、d与土体初始塑性模量的关系,并将土体的基本物理性质指标剪切波速引入到蛋形参数中；结合已有的文献资料,根据蛋形屈服函数形状参数α与tanφ的变化规律,发现具有一致性,提出了α的取值方法。通过一系列室内试验定量地给出了蛋形屈服面参数与土体初始剪切波速和内摩擦角的相关关系。 4、在初始弹性模量计算公式中引入结构屈服应力po来代替大气压力p。,提出了考虑结构性影响的初始弹性模量计算公式,并建立了公式中试验常数和初始剪切波速的相关关系。在增量塑性理论框架下,以蛋形加载函数为加载面,以塑性功函数为硬化参数,运用相关联流动法则,建立了结构性土体的蛋形屈服面弹塑性模型。基于一系列应力路径压缩试验、常规三轴剪切试验数据,确定了该模型参数的取值。并进一步将剪切波速这个土体基本物理性质指标引入到模型参数中,通过相应的弯曲元剪切波速测试试验定量的给出了模型参数与土体初始剪切波速的相关关系。 5、介绍了弹塑性有限元数值分析的研究现状,采用修正牛顿-拉弗森常刚度迭代法结合隐式回归本构积分算法,并应用位移控制法理论建立了蛋形屈服面弹塑性模型的有限元程序。进行三轴试验条件下的应力-应变关系数值模拟,给出三轴试验中圆柱体试块的应力-应变变化规律,验证了本构关系的合理性；最后结合—挡土结构被动土压力的数值算例,验证了新建有限元程序分析结果的可行性。
[Abstract]:Soft clay is widely present in the coastal and some inland river cities in the southeast of China (such as Wuhan, Kunming, etc.), and the engineering quantity is huge. Although the existing soil mechanics theory has a certain guiding function to the engineering practice, the fact shows that the effect is limited. Most of the theory about the strength and deformation of the soil is the research result of the continuous medium as the object, and it is applied to the non-continuous and structural medium such as the soil, and the purpose of the real engineering problem is not achieved, such as: Most of the existing constitutive models of the soil have not fully considered the physical characteristics of the soil, the uncertainty of the model parameters is too large, the calculation results of the stress and strain are too large, and there are obvious defects in the engineering application. In this paper, based on the characteristics of the soil non-continuous medium and the strong structure, this paper uses the new technology of modern test (bending element shear wave velocity test) to explore the new method to describe the structure of the soil body through the combination of the micro-structure analysis test of the soil and the test of the macro-mechanical property. The stress state equation of soil is set up, the new strength criterion of the soil body is put forward, and a new method for predicting the compression property of the structural soil is set up, and the physical and mechanical constitutive model of the soil is established. And through the numerical analysis, the new theoretical results are applied to solve the practical engineering problems. In this paper, the stress state, strength and deformation law of the non-continuous soil body are of great theoretical significance and application value. The main research contents and results are as follows: Next:1. According to the non-continuous property of the soil, the physical property index of the porosity is introduced, the stress state equation of the soil body is established, and the existing strength theory (such as the Mohr-Coulomb's theory) is pointed out by the comparative analysis. Based on a series of conventional three-axis consolidation and compression tests, the mechanical properties of different initial pore ratio and plastic index are analyzed on the basis of a series of conventional three-axis consolidation compression tests. In this paper, a new physical parameter model is proposed, which can comprehensively reflect the mineral content and the state of the normal consolidated saturated clay, and establish the relationship between the index of the shear strength and the strength of the clay, and further consider the entry into the Mohr-Coulomb criterion. Line correction.2. Based on the structural damage compression model of Liu and Carter, a simplified physical property change parameter is proposed: the relative change index (Ev) of the pore is considered, and the effect of initial pore change on the soil compression property is considered, and different initial vibration of the original soft soil in Hangzhou is carried out. In this paper, the relationship between the relative change index (Ev) of the pore and the yield stress of the soil structure and the structural damage index (b) is established, and a new method for predicting in-situ compression using the results of the indoor compression test is proposed. The method for determining the parameters of the egg-shaped yield function is discussed. The relationship between the parameters a, b and d of the egg-shaped yield function and the initial plastic modulus of the soil is established, and the shear wave velocity of the basic physical properties of the soil is introduced into the egg-shaped parameters. according to the shape parameters of the egg-shaped yield function and the variation law of the tan, the paper finds that the method has the advantages of consistency, By a series of indoor tests, the parameters of the egg-shaped yield surface and the initial shear wave velocity and the internal friction of the soil body are given in a quantitative way. In this paper, a formula for calculating the initial elastic modulus considering the structural influence is put forward, and the test constant and the initial elastic modulus are set up in the formula. In the framework of incremental plastic theory, the egg-shaped loading function is taken as the loading surface, the plastic work function is the hardening parameter, the associated flow rule is used, and the egg of the structural soil body is established. The elastic-plastic model of the yield surface of the shape. Based on a series of stress path compression tests, the conventional three-axis shear test data is determined. The value of the model parameters is given, and the basic physical property index of the shear wave velocity is introduced into the model parameters, and the model parameters and the initial soil mass are given by the corresponding bending element shear wave velocity test. In this paper, the relation of shear wave velocity is discussed.5. The present situation of the elastic-plastic finite element numerical analysis is introduced. The implicit regression constitutive integral algorithm is combined with the modified Newton-Laver's constant-stiffness iterative method, and the egg-shaped yield surface is established by the theory of displacement control method. The finite element program of the elastic-plastic model is given. The stress-strain relation numerical simulation under the three-axis test condition is carried out. The stress-strain variation rule of the cylinder block in the triaxial test is given, and the rationality of the constitutive relation is verified. A numerical example of the pressure of passive earth is given, and the new finite element method is proved.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU43
本文编号：2507834
[Abstract]:Soft clay is widely present in the coastal and some inland river cities in the southeast of China (such as Wuhan, Kunming, etc.), and the engineering quantity is huge. Although the existing soil mechanics theory has a certain guiding function to the engineering practice, the fact shows that the effect is limited. Most of the theory about the strength and deformation of the soil is the research result of the continuous medium as the object, and it is applied to the non-continuous and structural medium such as the soil, and the purpose of the real engineering problem is not achieved, such as: Most of the existing constitutive models of the soil have not fully considered the physical characteristics of the soil, the uncertainty of the model parameters is too large, the calculation results of the stress and strain are too large, and there are obvious defects in the engineering application. In this paper, based on the characteristics of the soil non-continuous medium and the strong structure, this paper uses the new technology of modern test (bending element shear wave velocity test) to explore the new method to describe the structure of the soil body through the combination of the micro-structure analysis test of the soil and the test of the macro-mechanical property. The stress state equation of soil is set up, the new strength criterion of the soil body is put forward, and a new method for predicting the compression property of the structural soil is set up, and the physical and mechanical constitutive model of the soil is established. And through the numerical analysis, the new theoretical results are applied to solve the practical engineering problems. In this paper, the stress state, strength and deformation law of the non-continuous soil body are of great theoretical significance and application value. The main research contents and results are as follows: Next:1. According to the non-continuous property of the soil, the physical property index of the porosity is introduced, the stress state equation of the soil body is established, and the existing strength theory (such as the Mohr-Coulomb's theory) is pointed out by the comparative analysis. Based on a series of conventional three-axis consolidation and compression tests, the mechanical properties of different initial pore ratio and plastic index are analyzed on the basis of a series of conventional three-axis consolidation compression tests. In this paper, a new physical parameter model is proposed, which can comprehensively reflect the mineral content and the state of the normal consolidated saturated clay, and establish the relationship between the index of the shear strength and the strength of the clay, and further consider the entry into the Mohr-Coulomb criterion. Line correction.2. Based on the structural damage compression model of Liu and Carter, a simplified physical property change parameter is proposed: the relative change index (Ev) of the pore is considered, and the effect of initial pore change on the soil compression property is considered, and different initial vibration of the original soft soil in Hangzhou is carried out. In this paper, the relationship between the relative change index (Ev) of the pore and the yield stress of the soil structure and the structural damage index (b) is established, and a new method for predicting in-situ compression using the results of the indoor compression test is proposed. The method for determining the parameters of the egg-shaped yield function is discussed. The relationship between the parameters a, b and d of the egg-shaped yield function and the initial plastic modulus of the soil is established, and the shear wave velocity of the basic physical properties of the soil is introduced into the egg-shaped parameters. according to the shape parameters of the egg-shaped yield function and the variation law of the tan, the paper finds that the method has the advantages of consistency, By a series of indoor tests, the parameters of the egg-shaped yield surface and the initial shear wave velocity and the internal friction of the soil body are given in a quantitative way. In this paper, a formula for calculating the initial elastic modulus considering the structural influence is put forward, and the test constant and the initial elastic modulus are set up in the formula. In the framework of incremental plastic theory, the egg-shaped loading function is taken as the loading surface, the plastic work function is the hardening parameter, the associated flow rule is used, and the egg of the structural soil body is established. The elastic-plastic model of the yield surface of the shape. Based on a series of stress path compression tests, the conventional three-axis shear test data is determined. The value of the model parameters is given, and the basic physical property index of the shear wave velocity is introduced into the model parameters, and the model parameters and the initial soil mass are given by the corresponding bending element shear wave velocity test. In this paper, the relation of shear wave velocity is discussed.5. The present situation of the elastic-plastic finite element numerical analysis is introduced. The implicit regression constitutive integral algorithm is combined with the modified Newton-Laver's constant-stiffness iterative method, and the egg-shaped yield surface is established by the theory of displacement control method. The finite element program of the elastic-plastic model is given. The stress-strain relation numerical simulation under the three-axis test condition is carried out. The stress-strain variation rule of the cylinder block in the triaxial test is given, and the rationality of the constitutive relation is verified. A numerical example of the pressure of passive earth is given, and the new finite element method is proved.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU43
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