非饱和黏土动态力学特性及其本构关系研究

发布时间：2018-06-09 23:57

本文选题：非饱和黏土 + 本构模型　；参考：《国防科学技术大学》2013年博士论文

【摘要】：土作为一种最普遍的基层材料,广泛应用于各类民用和国防工程建设。土基层以及土中构筑物在其工作过程中,除了承受正常的设计载荷外,可能还要承受诸如撞击、冲击和爆炸等强动载荷。黏土的分布广泛,且通常情况下,黏土均处于非饱和状态。非饱和黏土是一种力学性质极为复杂的材料,并且针对非饱和黏土的动态本构建模至今仍然是不完备的,因此有必要对非饱和黏土的动态本构关系进行深入系统研究。非饱和黏土的动态力学特性受多种因素影响,主要包括初始密度(压实度)、含水率(饱和度)和外载荷特性(应力水平、加载速率)等。为探讨分析以上影响因素的影响规律,本文结合非饱和黏土的材料特性,设计开展了针对不同初始密度、含水率的非饱和黏土试样的静、动态力学系列试验。其中,静态力学试验主要包括:无侧限压缩试验和三轴剪切试验;动态力学试验主要包括:单轴压缩SHPB试验、被动围压SHPB试验和平板撞击试验。通过对试验结果的分析,得出了非饱和黏土在静、动态加载条件下的力学特性,归纳总结了初始密度、含水率和外载荷特性等因素的影响规律。本文提出应用基于Perzyna形式的黏塑性帽盖模型描述非饱和黏土的屈服破坏行为;提出将p-??物态方程和修正三相混合物物态方程结合起来,描述非饱和黏土在高压状态下的压力-密度关系。基于非饱和黏土静、动态力学试验结果,提出了一套确定黏塑性帽盖模型和物态方程参数的方法。为验证基于Perzyna形式的黏塑性帽盖模型和非饱和黏土物态方程及其参数的适用性和准确性,分别以用户自定义材料模型和自定义物态方程子程序的形式将帽盖模型和物态方程嵌入到LS-DYNA软件中,并对非饱和黏土中动力学过程进行了数值模拟。模拟结果表明,基于Perzyna形式的黏塑性帽盖模型和非饱和黏土物态方程及其参数能够较为准确地描述非饱和黏土的动态力学行为。
[Abstract]:As the most common base material, soil is widely used in various civil and national defense projects. In addition to the normal design load, the soil base and the structure in the soil may also bear strong dynamic loads such as impact, impact and explosion. The clay is widely distributed, and usually, the clay is in unsaturated state. Unsaturated clay is a kind of material with very complex mechanical properties, and the dynamic constitutive model of unsaturated clay is still incomplete, so it is necessary to study the dynamic constitutive relationship of unsaturated clay. The dynamic mechanical properties of unsaturated clay are affected by many factors, including initial density (compactness), water content (saturation) and external load characteristics (stress level, loading rate). In order to analyze the influence law of the above factors, the static and dynamic mechanical tests of unsaturated clay samples with different initial density and moisture content were designed and carried out in this paper. Among them, static mechanical test mainly includes: unconfined compression test and triaxial shear test, dynamic mechanical test mainly includes: uniaxial compression SHPB test, passive confining pressure SHPB test and plate impact test. Through the analysis of the test results, the mechanical properties of unsaturated clay under static and dynamic loading conditions are obtained, and the influence laws of initial density, moisture content and external load characteristics are summarized. In this paper, a viscoplastic cap model based on Perzyna form is proposed to describe the yield failure behavior of unsaturated clay. The equation of state is combined with the modified equation of state of three-phase mixture to describe the pressure-density relationship of unsaturated clay under high pressure. Based on the static and dynamic mechanical test results of unsaturated clay, a set of methods for determining the parameters of visco-plastic cap and equation of state are presented. In order to verify the applicability and accuracy of the viscoplastic cap model and the equation of state of unsaturated clay based on Perzyna form, The cap model and the equation of state are embedded into LS-DYNA software in the form of user-defined material model and self-defined equation of state subroutine respectively. The dynamic process in unsaturated clay is simulated numerically. The simulation results show that the viscoplastic cap model and the equation of state of unsaturated clay based on Perzyna form can accurately describe the dynamic mechanical behavior of unsaturated clay.
【学位授予单位】：国防科学技术大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TU411;TU435

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