裂隙性黏土的强度尺寸效应与局部应变软化机理研究

项目以裂隙作为一个隐形诱因是引发边坡渐进式破坏等灾害的重要因素之一为背景，以深化认知裂隙对天然黏土力学行为的控制机理为主线，采用地质调查→原位、室内、细微观试验→机理分析→指导与应用的研究思路，多角度调查土的裂隙成因与物源，提出一套裂隙发育特征的定量评价体系与分级标准；开展不同尺寸试样的剪切试验并以原位试验作为参考性试验，建立强度与试样尺寸的非线性关系，提出考虑裂隙尺寸效应影响的试样临界尺寸、强度辨识方法与取值建议；通过测试局部变形、孔压与剪切波速的三轴剪切试验，研究裂隙的扩展与贯通过程对局部变形和剪切带破坏的影响；借助微米级CT对剪切全过程跟踪扫描，研究随应变发展三维裂隙结构的演化规律，寻找到与强度特征与变形特性最敏感的细微观裂隙结构参数；跨尺度耦合分析上述试验结果，最终阐明裂隙性黏土的强度尺寸效应与局部应变软化机理，为我国裂隙土工程的稳定性评价及灾害预测与治理提供理论支持与技术指导。

Fissure in soils, one of the potential predisposing factors of engineering disasters such as progressive failure of slopes, has long been a topic of interest in engineering geology and soil mechanics. In this study, various scales of surveys and investigations will be performed, including geological investigation of studied sites, in-situ and laboratory tests, mini- and micro-experiments of studied fissured soils. Afterward, a multi-scale coupling mechanism analysis will be carried out with an aim of acquiring an insight into the mechanical behavior of fissured clay. This research will be organized as follows. As first, a quantitative framework of fissure characterization and grading will be proposed based on the analysis of the provenance and formation of studied soil. Thereafter, the relationship between strength and sample size will be established via a series of triaxial tests on samples with various dimensions and in-situ tests. And the critical dimension of samples for laboratory tests, recommended value for shear strength and its determination will be suggested considering the size effect of fissured soil specimens. Besides, the effect of fissure development on local deformation and the formation of the shear band will be ascertained through special triaxial tests with local deformation, pore pressure and shear wave velocity measured. Furthermore, the evolution of three-dimensional fissure structure during the triaxial test will be traced simultaneously using computed tomography (CT) and fissure-sensitive microstructure parameter will be proposed accordingly. Finally, the mechanism that fissure controls the mechanical behavior of natural clay will be revealed based on the findings of the experiments above. The results of this research can lead to a deeper understanding of fissured soil behavior and provide theoretical support and technical guidance for the forecast, controlling and comprehensive treatment of the disasters relevant to fissured clay.