基于三相耦合性态的非饱和黄土动残余应变理论估算模型

Dynamic deformation of unsaturated soil is one of key and outsanding research problems in the geotechnical earthquake engineering field. Generally, the nature loess is a special/typical kind of unsaturated soil, coupling with triphase of solid, water and air. Its deformation response under complicated dynamic loading, especially the strong ground motion, is influenced by the triphase performance jointly as well. According to the facts of volume variation and triphase-coupling effect during the generation process of dynamic residual strain (DRS) of unsaturated loess, here, the applicant would provide a theoretical estimation model for DRS of unsaturated loess through investigating two quantitative relations of triphase volume deformation (TVD) and dynamic void deformation response (DVDR), by which the corresponding formulas to describe TVD and DVDR respectively would be established. In the project, the coupling relation of TVD could be deduced theoretically by analyzing the basic physical process and actual mechanical mechanism of DRS of unsaturated loess under dynamic loading. Based on dynamic triaxial test and triphase-coupling-performance simulation test in laboratory and theoretical analysis method, meanwhile, the theoretical coupling relation of DVDR would be proposed, in which critical influence parameters of DRS of unsaturated loess, structure strength, external dynamic loading and field consolidation stress, could be considered comprehensively. Consequently, a triphase-coupling-based theoretical model to estimate DRS of unsaturated loess would be proposed due to the theoretical inherent connection between TVD and DVDR obtained by the above-mentioned analysis of physical process and mechanical mechanism. The rationality and applicability of the triphase-coupling-based theoretical model, furthermore, will be verified carefully by laboratory data of geotechnical test and dynamic triaxial test. In this research project, the key scientific problem derives from the hot spots of research conundrum in the interdiscipline between geotechnical engineering and earthquake engineering. Both of substances and thoughts in this research, moreover, are new and innovative. For the special kind of soil, unsaturated loess, the expected results of this research application will be helpful to understand its dynamic deformation characteristics and to obtain a corresponding constitutive model with better rationality and applicability on DRS. In summary, this application has an obvious significance at the aspects of science and practice to develop the understanding on relative scientific problems in the research field of geotechnical earthquake engineering.

非饱和土动力变形特性，是岩土地震工程领域仍未解决的重要科学问题。天然黄土属于典型的非饱和土，动力形变亦受固、水、气三相性态共同制约。本项申请以非饱和黄土产生动残余应变时的体积变化与三相耦合作用的事实为基础，将土体动残余应变估算拆解为研究三相体积形变和孔隙形变动力响应等两方面的理论耦合关系。通过分析动残余应变基本物理过程与实际力学机制，推导非饱和黄土三相体积形变耦合关系；联合室内动三轴实验、三相耦合性态模拟实验及理论分析方法，建立考虑土体结构强度、加载动应力和场地固结应力等关键影响参量的孔隙形变动力响应耦合关系。借助两个耦合关系，分析构建基于三相耦合性态的非饱和黄土动残余应变的理论估算模型；利用室内土工测试与动三轴实验数据，对该理论估算模型的合理性与适用性进行检验。本项申请立足国内外岩土工程与地震工程交叉领域热点关注的科学难题，研究内容和思路皆具创新性，预期结果具有科学和应用方面的重要意义。

非饱和黄土的动力变形性态，是岩土地震工程研究领域的重要问题。非饱和黄土为固、水、气三相耦合体，动力变形性态受三相赋存特性共同制约。作为非饱和土力学研究的基石，以三相赋存概念为出发点的非饱和土本构关系研究（静载条件）仍处发展阶段，与之相关的动力本构关系研究（动载条件）尚处起步伊始。这不仅是研究工作量的问题，也是测试技术仍待提高以及科学问题基本物理过程认知亟待提升的必然结果。.项目通过非饱和黄土固、水、气三相耦合性态模拟试验，深入分析了非饱和土固相与水气相介质之间的相互作用以及非饱和与饱和黄土动力响应机制的一致性。结合土体变形协调分析，建立了非饱和黄土固、水、气三相体积形变的理论耦合关系；借助土体动力综合耐受特性分析，区分了非饱和黄土水气两相孔隙形变动力响应过程的3个阶段。综合起始动应力与结构强度定量关系、极限动残余应变与可压缩孔隙比理论关系以及动残余应变非线性特征理论描述等方面的针对性分析，给出了非饱和黄土动残余应变的实用性理论估算模型，并据此提出了非饱和黄土场地动残余应变的概率性评价方法。研究取得的关键创新性成果总结如下。.（1）基于土体残余变形控制孔隙气（水）压力的联合分析，揭示了孔隙气、水压力在外部荷载响应过程与成因上的一致性，厘定了气体相对孔隙气压力、水体相对孔隙水压力绝对量值的差异性贡献。.（2）借助加载应力、残余变形和孔隙压力的相关性分析，明确了残余变形与孔隙压力之间的因果关系，得出了非饱和黄土动残余应变的关键控制参量。.（3）基于土体渗透特性细观影响参量分析，应用等效性原理推导了完全等效土体渗透通道的等效渗透管径计算公式，结合泊肃叶定律建立了土体渗透系数理论估算模型。.（4）以建立的非饱和黄土固、水、气三相体积变形理论关系与水、气两相孔隙形变动力响应耦合关系为基础，采用非饱和黄土动残余变形三阶段过程关键特征的定量分析，提出了非饱和黄土动残余应变的实用性理论估算模型。.（5）借助概率统计理论与蒙特卡洛模拟方法，给出了非饱和黄土场地宏观动力沉降风险的分析思路，提出了非饱和黄土场地动残余应变（震陷性）及震陷量值的概率性评价方法。.上述成果是推进目前国内外非饱和黄土动残余应变本构关系基础研究的重要进展。成果的核心内容，已在2013年岷县漳县6.6级地震灾后恢复重建区地震地质灾害危险性与地震动场地效应区划以及异地重建集中安置点工程场地地震安全评估等项目中得到应用。