【作者】 刘珊；

【导师】 马金荣；

【作者基本信息】 中国矿业大学 ， 岩土工程， 2014， 硕士

【摘要】 天然岩土材料是具有一定结构性的复杂材料，其结构性问题一直是岩土工程领域的前沿问题和研究难点。土体宏观力学性质与其微观结构变化是相互联系的，因此如何考虑和描述结构性对土宏观力学性质与工程特性的影响具有重要的理论意义与实践意义。本文以徐州地区广泛分布的Q3黏土为研究对象，在宏观与微观试验研究基础上，较为系统的总结了结构性黏土的力学特性以及微观结构演变的规律；并以临界状态理论为出发点，提出了结构性临界状态本构模型。论文为进一步从宏微观结合揭示结构性土体变形机理奠定了研究基础。以下为主要研究内容与创新性成果：1.在对受轻微扰动的原状Q3黏土与相应重塑土样进行一维固结试验的基础上，分析了结构屈服应力、应力历史对土体固结特性的影响；2.鉴于以往试验研究大多不能反映土体实际固结状态以及应力水平较低的情况，采用GDS三轴试验系统进行了中高压条件下的固结三轴不排水剪切试验并结合重塑土样做了平行对比试验，分析了值变化规律以及前期固结压力、应力路径等条件对结构性土变形和强度的影响；并利用轻微扰动原状土与重塑土样的试验结果差异建立起结构性强度作为衡量土体结构性强弱的指标；3.上述试验结果表明结构性土体在受力破坏时也存在着唯一的最终状态。因此，基于临界状态理论建立了可以反映结构性土体力学特性的弹塑性本构模型，模型的特点在于引入初始各向异性张量来反映天然土体在固结后所具有的初始结构性与各向异性，并将结构强度引入到结构性参数中，建立起结构性参数随着变形衰减的硬化规律来反映土体受荷扰动后出现结构性破坏的过程；通过与部分试验结果的比较，初步验证了模型可较为合理的反映出Q3黏土的显著结构性以及荷载作用下产生的应变软化现象。4.选取重塑土和轻微扰动原状土在不同试验阶段的试样进行了扫描电镜等试验，从颗粒和孔隙的几何形态、表面特征等角度重点分析了固结对土体的微观形态的影响，并初步从微观定量化角度去解释土体宏观力学行为，得到了Q3黏土在不同应力路径三轴剪切条件下定量化微结构形态的演化规律。更多还原

【Abstract】 Research on the micro-structure of natural geotechnical material, which generally has astrong and complex structure, has been the difficult point and forefront. The macro characteristicsare concerned with the change of the microstructure, so to find out the evolvement rule of themicrostructure can provide the foundation to the research of the mechanical properties and clarifythe damage reasons of the geological engineering structure. In this paper, both methods of macrotest and micro-structural analysis are used to study Xuzhou Q3clay. The mechanicalcharacteristics and the micro-structural evolution of the structured clay are researched, and acritical state constitutive model has been proposed. Research in this paper can further provide thefoundation to the research of the mechanical properties.The main research contents and innovation achievements are as follows:1. One-dimensional consolidation tests have been conducted to study the influence ofstructure yield stress and stress history on undisturbed and remolded clay.2. By using GDS triaxial apparatus, consolidation triaxial tests under middle-highpressure have been conducted to study the mechanical characteristics of clay samples withdifferent stress paths and different pre-consolidation pressure. According to the macro test data,the difference of undisturbed and remolded clay samples are discussed, which should be as areflection of structure stress.3. Structure clay has the certain final state so that a critical state constitutive model has beenproposed to reflect the structure properties. In this model, the initial anisotropy tensor was beenintroduced to reflect the initial structural and anisotropy after consolidation. The structuralparameter has been used to describe the structural failure under disturbance of load. This modelhas been proved to be suitable by comparing with part of test data.4. Parallel tests are conducted to study the micro-structural morphology in the process of consolidation tests and triaxial tests. Amount of SEM pictures are taken by the Scanning ElectronMicroscope, and by working with those pictures we can obtain the information of themicro-structural parameters. The evolution of micro-structural parameters along with the consolidation strain and the different stages of triaxial tests with different stress paths anddifferent pre-consolidation pressure are also discussed in this paper.This thesis has79figures,18tables and referred to109articles.更多还原