【作者】 夏旺民；

【导师】 郭增玉；

【作者基本信息】 西安理工大学 ， 岩土工程， 2005， 博士

【摘要】 本文通过不同初始含水量的Q4黄土及不同初始含水量和干容重的重塑黄土常规三轴、高压固结、湿陷和增湿试验,深入分析了黄土的变形强度特性、结构性以及湿陷和增湿变形特性,在此基础上建立了体现黄土结构性的弹塑性损伤本构模型,编制了黄土的入渗和弹塑性损伤平面有限元程序,对-自重湿陷黄土浸水试坑进行了数值分析。通过研究,本文主要取得了如下一些有益的成果:通过对Q4黄土和重塑黄土的常规三轴、高压固结、湿陷和增湿试验的数据分析,在充分认识黄土的变形强度特性、湿陷和增湿变形特性的基础上提出了一种用原状黄土、重塑饱和黄土割线模量表示的黄土结构性参数。该参数可以较好反映黄土在加载和增湿作用下结构变化和破损的过程。根据热力学和连续损伤力学理论以及黄土在加载和增湿作用下的能量转换过程,提出了黄土的损伤变量、加载损伤和增湿损伤的定义以及它们之间关系,提出了由塑性、加载损伤和增湿损伤三部分组成的黄土弹塑性损伤本构模型的基本构架。其中,首次提出黄土的增湿损伤变量的定义及与含水量有关的增湿损伤等效能量指标,描述增湿损伤的演化过程;参照Simo提出的能量指标概念,定义黄土的加载损伤的能量指标,并通过黄土加载过程中的结构破损、力学和强度指标的劣化分析,确定黄土的加载损伤演化方程;结合以塑性功为硬化参数的椭圆形屈服面,根据相关联流动法则及损伤理论推导出了黄土弹塑性损伤本构模型。将模型计算结果与试验数据比较,表明该模型可以模拟黄土的不同应力应变曲线类型,并可以通过损伤变量来控制应力应变曲线的转型,同时还可以模拟黄土的增湿变形和湿陷变形过程;计算结果与试验数据基本接近,只是低含水量情况下的计算结果稍有差异。摘要早鱼旦皿口且口里旦皿胆里旦旦旦旦 根据黄土的入渗特点和非饱和土渗流理论,运用Mat lab有限元工具箱编制了黄土入渗的平面有限元程序,计算结果符合实际。同时根据弹塑性损伤本构模型和非线性有限元理论,运用matlab有限元工具箱还编制了可以考虑加载和增湿条件的黄土弹塑性损伤平面有限元程序。最后将入渗程序和弹塑性损伤程序结合对一自重湿陷黄土浸水试坑进行数值分析,表明程序计算结果符合黄土的湿陷和增湿变形发展实际过程。同时可以根据计算损伤变量的分布规律可以预测黄土的湿陷变形区的发展范围.程序可用于各种黄土工程变形与稳定问题的计算,为黄土的加载变形特性、湿陷和增湿特性研究的验证提供了一种新的途径和方法.关键词:黄土结构性参数增湿损伤加载损伤弹塑性本构模型 非线性有限元更多还原

【Abstract】 In this paper, by means of conventional tri-axial test, high-pressure consolidation test, collapse and moistening test of intact loess Q4 sample with different initial water content and remolded loess sample with different initial water content and different initial dry unit weight, the deformation and strength characteristics, soil structure characteristics, collapse deformation and moistening deformation characteristics of both loess were analyzed. On this basis the elasto-plastic damage constitutive model of loess which can materialize soil structure characteristics were established. The infiltration and elasto-plastic damage 2D FE programs of loess were coded and taken into numerical analysis of a soaking test pit with self weight collapsible loess. Some useful results were found after those.Firstly, analyzed data of tri-axial test, high-pressure consolidation test, collapsible and moistening test of intact loess Q4 and remolded loess, and on basis of deeply studying the deformation and strength characteristics, collapse and moistening deformation characteristics of loess, a soil structure parameter was put forward with the secant modulus of intact loess and remold saturated loess, which can well reflect the loess structure changing and damaged process under loading and moistening.Secondly, based on the theory of thermodynamics and continuum damage mechanics and the energy conversion of loess in load and moistening, the damage variable, load damage and moistening damage of loess and their relations were put forward. The basic framework of the elasto-plastic damage models of loess which were made up of plastic, load damage and moistening damage were also put forward. For the first time the definition of the loess moistening damage variable was put forward, aswell as the equivalent energy index of loess moistening damage which relates to the water content or the saturation degree to describe the moistening damage evolvement procedure. Based on the concept of Simo’s energy index, the energy index of loess load damage was put forward. And analyzed structure breakage and degradation of mechanic and strength index, the evolvement procedure of loess load damage was put forward. To join ellipse yield function, hardening parameter with plastic work, associated flow law and damage theory, the elasto-plastic damage constitutive model of loess were derived. Compared the calculation results of model to tests data, it shows that they were close basically, only a few difference in low water content, that means the model can simulate different stress-strain curve types of loess, can control the transition of the stress-strain curve through damage variable, and also can simulate the moistening deformation and collapse deformation.Finally, according to the infiltration characteristics of loess and the permeation theory of unsaturated soils, a 2D FE program of loess infiltration was coded by Matlab finite element toolbox, and its numeration results were fit to practice. Another 2D FE program of elasto-plastic damage models of loess was also coded by Matlab finite element toolbox, based on the elasto-plastic damage models and the theory of nonlinear finite element. These two programs were used to the calculation of a soaking test pit with self weight collapsible loess, and the numerical results were fit to the practical development procedure of the loess collapse and moistening deformation. Also, the loess collapse deformation area could be predicted according to the distribution law of damage variable. Furthermore, the programs can be applied to calculate the deformation and stability of loess projects, and to provide a new way and method to verify the researches of the load deformation characteristics, collapse and moistening characteristics.更多还原