结构性黏土力学特性与微观形态试验研究

发布时间：2018-01-11 11:05

本文关键词：结构性黏土力学特性与微观形态试验研究　出处：《中国矿业大学》2014年硕士论文　论文类型：学位论文

【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。
[Abstract]:Natural rock and soil material is a complex material with a certain structure , and its structural problems have been a leading problem in the field of geotechnical engineering . The macroscopic mechanical properties of soil and its microstructure change are interrelated , so how to consider and describe the mechanical properties of structural clay and the evolution of microstructure are systematically summarized . The following are key research content and innovative results : 1 . On the basis of one - dimensional consolidation test on undisturbed Q3 clay and corresponding remolded soil sample , the influence of structure yield stress and stress history on consolidation characteristics of soil body is analyzed . 2 . In view of the fact that most of the previous researches do not reflect the actual consolidation state of soil and the low stress level , the consolidation triaxial undrained shear test under the medium and high pressure conditions is carried out by adopting the triaxial triaxial test system , and the influence of the conditions on the deformation and the strength of the structural soil is analyzed by combining the remolded soil sample , and the structural strength is established as an index for measuring the structural strength of the soil body by using the difference of the test results of the undisturbed soil and the remolded soil sample ; 3 . Based on the theory of critical state , an elastic - plastic constitutive model which can reflect the mechanical properties of the structural soil is established . The model is characterized by the introduction of the initial anisotropic tensor to reflect the initial structural and anisotropy of the natural soil after consolidation , and the structural strength is introduced into the structural parameters . 4 . The influences of consolidation on the micro - morphology of soil mass were analyzed from the point of geometry and surface characteristics of particles and pores , and the macro - mechanical behavior of soil mass was analyzed from the micro - quantitative angle .

【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU442;TU43

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