基于介质细观物理构成特性的散粒体抗剪强度理论模型

The mechanical property of granular materials is among the most interesting field of mechanics because the area of its application is very wide. To disclose its essential mechanism by means of micro- and meso-scale level confirms to the overall developing trend of relative research problems both at home and abroad, as well as its theoretical description due to the mechanism. The core purpose of this research project is to find a method establishing theoretical model for shear strength of granular materials based on physical property analysis of medium composition by a comprehensive multi-angle. This project plans to combine several aspects of laboratory tests, i.e. physical property, particle size analysis, micro-structure, shear strength and loading CT, and particle numerical simulation and theoretical analysis for accomplishing relative research works. Based on the analysis of disturbing movement mechanism of solid particles within granular materials under external loadings, it is proposed of that a meso-scale mathematical formulation figures the structural resistance of particle system while the material suffers deformation due to external loadings. Then a theoretical meso-scale model of shear strength of granular materials is constructed by means of that analyze the balance relationship between stress conditions of external loadings and structural resistance of solid particle system on the shear interface within the media. Relative research works of this project presupposes developing trends of mechanical property of granular materials at home and abroad, and their thoughts are dealing with a specifically limit problem from the complicated object based on the further understanding of two aspects of key scientific issues. The innovated results of this project may be that reasonably introduce the quantitative influence of physical properties of medium composition on stress transfer of particle system and analyze the balance relationship of external stress and internal resistance on the shear interface within granular material.

散粒体力学特性研究是力学领域最受关注的问题之一，从微细观层面精细化揭示其本质机制并加以理论描述是国内外相关研究发展的总体趋势。本项申请的核心目的，是基于介质物理构成特性的解析，综合多元细观角度寻求理论描述散粒体抗剪强度的方法。研究过程中，拟结合室内常规物性测试、粒度分析、微结构测试、抗剪强度测试、加载CT测试、颗粒数值分析和理论分析，在研究外部荷载作用下散粒体固相颗粒间应力传递机制的基础上，给出散粒体受荷变形时颗粒结构体系抗力的细观表达形式，进而通过对外部荷载应力条件与颗粒结构体系抗力在剪切界面上的应力平衡分析，建立散粒体抗剪强度的理论模型。本项申请以符合国内外相关研究发展趋势为前提，以解决对象复杂性的有限问题为方向，以明确关键科学问题所在及解决要点为支撑，在合理引入散粒体介质细观物理构成特性对颗粒体系应力传递的定量影响、剪切界面上外部应力与内部抗力之间的平衡关系分析等两方面具有创新性。

散粒体力学特性研究是力学领域最受关注的问题之一，内涉复杂性在相关研究领域构成持续挑战。项目组发现，利用土体动力耐受特性参量估算其动力非线性变形时，强烈依赖于抗剪强度试验数据的准确性。研究试图从材料的物理构成特性入手，探究颗粒介质结构体系抗力的细观表达形式，建立散粒体抗剪强度的理论模型。.通过实施散粒体固相颗粒间的应力传递机制、颗粒结构体系抗力细观表达形式和基于剪切界面平衡分析的抗剪强度理论模型等三项内容，取得了若干具有学术价值的进展：(1)提出了用来分析散粒体细观构成特性的颗粒接触度均值距离的概念，将数学形式用于揭示颗粒介质的配位数、渗透系数和接触结构可变性名义密度指数，验证了接触度均值距离具有的可延拓性理论意义；(2)提出了针对颗粒介质的应力传递扩展角概念，得出了结构体系抗力的力学来源、作用模式和估算方法，给出了应力扩展角与内摩擦角的定量关联；(3)借助散粒体的破坏过程分析，揭示了剪切面空间展布与外部荷载几何约束间的作用关系，厘定了天然黄土屈服破坏和完全破坏的特征差异，得出了起始动应力和破坏应力界限的经验算法；(4)采用颗粒介质遵循均匀散布配位的假定，推导了内摩擦角正切值的理论表达形式，基于粘聚力的围压效应化处理，建立了可考虑介质各项异性的抗剪强度的理论模型，提出了修正应用该理论关系的优化方法。.散粒体细观力学机制的研究难点，与颗粒接触关系及相互作用过程的复杂性直接关联，研究结果的科学意义也与之呼应：(1)提出的分析颗粒接触特性的系列概念及数学形式，可在局部或全域考察颗粒细观作用模式的不确定性；(2)得出的应力传递扩展角和内摩擦角的定量关联，使颗粒的细观作用模式有迹可循，也使理论分析介质抗剪强度的各向异性特征成为可能；(3)建立的抗剪强度理论模型，兼备真实的物理背景和确然的作用过程，使其具有科学性与合理性，与之配套的计算参数不确定性的敏感度分析方法，也使其具有可靠性与适用性。