考虑黏聚强度的土的弹塑性损伤本构模型研究

发布时间：2018-04-02 20:22

本文选题：本构模型　切入点：黏聚强度　出处：《哈尔滨工业大学》2017年硕士论文

【摘要】：随着数值计算方法在土木工程领域的应用,土的本构关系成为重要研究课题。现有的很多土的本构模型都是基于重塑土而建立的,而重塑土因为经过了搅乱破坏了土颗粒间的联结、胶结作用,其力学性质简单。自然界中许多土,如原状土、改良土以及冻土等,土体内部颗粒间具有较强的胶结结构,宏观反映为土体黏聚强度,表现出与重塑土不同的力学性质。对于这类强结构性土,在加载过程中,颗粒间的胶结结构被破坏,使土体的黏聚强度降低,同时随着加载过程的进行,土体内部微裂纹不断扩展,表现为材料的损伤,这些都对土体力学性质有重要影响。所以用已有的重塑土模型不能很好的反映这类结构性土的力学特性。本文围绕黏聚强度和加载过程中的损伤机理,这两个因素对于土体力学性质的影响进行研究,主要完成了以下几个方面的工作:1、在土的经典弹塑性理论基础上,为了考虑结构性土的力学特性,基于上下加载面模型,通过引入黏聚强度及其损失规律来描述结构性土的力学特性,建立了考虑黏聚强度的土的弹塑性本构模型。在建立的考虑黏聚强度的结构性土的弹塑性本构模型中,对黏聚强度及其损失规律、超固结参数和结构性参数在不同条件下对土的力学特性的影响进行对比分析。结果表明黏聚强度和超固结对土体的软化、硬化、剪缩、剪胀等力学性质影响较大。利用该模型对水泥改良土的应力-应变关系进行了预测,并与试验结果进行对比分析,结果表明,建立的模型可较好地描述结构性土的剪缩硬化、剪胀软化等力学特性。2、根据结构性土的力学特性,在考虑黏聚强度的基础上,同时考虑加载过程中土的损伤及其演化规律,在连续介质损伤力学的框架内,结合上下加载面模型,研究了加载过程中土的损伤的演化规律,通过损伤与弹性、塑性的耦合,建立了考虑黏聚强度的弹塑性损伤本构模型,并用建立的模型对冻结盐渍土的三轴试验结果进行预测,并与试验结果对比,结果表明,建立的弹塑性损伤模型可以较好的描述结构性土的力学性质。3、采用了一种基于非线性最小二乘法的程序,用以实现本文提出的本构模型参数最优解的求解,并对参数取值范围对精度的影响进行研究。结果表明,所采用的程序具有很高的精度与运算速度,可以很好的完成模型参数最优解的求解。
[Abstract]:With the application of numerical method in the field of civil engineering, the constitutive relation of soil becomes an important research topic.Many existing constitutive models of soil are based on remolded soil, and the mechanical properties of remolded soil are simple because of its agitation and destruction of the bond between soil particles and cementation.In nature, many soils, such as undisturbed soil, improved soil and frozen soil, have a strong cementation structure between particles in the soil, which is reflected in the cohesive strength of the soil, showing different mechanical properties from the remolded soil.For this kind of strongly structured soil, the cemented structure between particles is destroyed during the loading process, and the cohesive strength of the soil decreases. At the same time, as the loading process goes on, the internal micro-cracks of the soil continue to expand, showing the damage of the material.All of these have an important effect on the mechanical properties of soil.Therefore, the existing remolded soil model can not well reflect the mechanical properties of this kind of structural soil.In this paper, the influence of these two factors on the mechanical properties of soil is studied around the cohesive strength and damage mechanism during loading. The main work of this paper is as follows: 1, based on the classical elastic-plastic theory of soil.In order to consider the mechanical properties of structural soil, based on the upper and lower loading surface model, the elastoplastic constitutive model of the soil with cohesive strength is established by introducing the cohesive strength and its loss law to describe the mechanical properties of the structural soil.In the elastoplastic constitutive model of structural soil considering cohesive strength, the effects of cohesion strength and its loss law, overconsolidation parameters and structural parameters on the mechanical properties of soil under different conditions are compared and analyzed.The results show that the cohesive strength and overconsolidation have great influence on the mechanical properties of soil such as softening hardening shearing and swelling.The model is used to predict the stress-strain relationship of cement modified soil, and the results are compared with the experimental results. The results show that the model can describe the shear shrinkage hardening of structural soil.According to the mechanical properties of structural soil, considering the cohesive strength, and considering the damage and evolution of soil during loading, in the framework of damage mechanics of continuous medium,Combined with the upper and lower loading surface model, the evolution law of soil damage during loading is studied. Through the coupling of damage, elasticity and plasticity, an elastic-plastic damage constitutive model considering cohesive strength is established.The established model is used to predict the triaxial test results of frozen saline soil, and the results are compared with the experimental results.The elastoplastic damage model can well describe the mechanical properties of structural soil. A program based on nonlinear least square method is used to solve the optimal solution of the constitutive model parameters proposed in this paper.The influence of parameter range on precision is also studied.The results show that the program has high precision and operation speed, and it can solve the optimal solution of the model parameters well.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU43

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