【作者】 邓国华；

【导师】 邵生俊；

【作者基本信息】 西安理工大学 ， 岩土工程， 2009， 博士

【摘要】 结构性是天然岩土材料的基本属性,其定性和定量上的复杂性致使土结构性的研究仍处于一个“百花齐放”的探索阶段。本文在总结土结构性及其力学效应研究成果的基础上,借助新开发的真三轴仪,在综合结构势理论的框架内,进一步深入认识了土结构性的变化规律,并探讨分析了结构性土的强度变形本构关系。主要的研究成果有：第一,调试和完善了西安理工大学自主研发的新型真三轴仪。解决了该仪器系统存在的几个关键技术问题,如液压囊漏水问题、排水控制问题、仪器系统误差分析、附属设备的设计等。同时,对试验方法进行翔实的总结,并提出了仪器系统尚存在的问题。第二,通过真三轴仪,研究了原状黄土、重塑黄土和饱和黄土的应力应变和体变特性。提出了一个可全面反映剪应力和球应力共同作用的结构性参数——应力比结构性参数,实现了应力空间内任意应力路径下对土结构性的描述。通过常规三轴试验和真三轴试验,系统地认识了土结构性的变化规律以及它与剪切变形、含水量、固结压力和应力路径之间的关系,建立了描述结构性变化规律的数学表达式,并揭示了真三轴条件下土样的四种破坏形式。第三,建立了土的强度与结构性之间的关系,提出了一个可考虑结构性的抗剪强度公式,分析了强度参数粘聚力和内摩擦角与结构性参数之间的关系。认为结构性参数比与强度比成正比关系,粘聚力与结构性参数符合近似的双曲线关系,当土的结构性遭到彻底破坏时,其粘聚力为0。摩擦角在结构性变化过程中基本不变。第四,分析了应力空间内土的强度破坏面,探讨了强度破坏面的大小和形状与结构性之间的关系。认为结构性较强时,粘聚分量对土强度的贡献较大,三轴压缩与三轴挤伸状态时土的强度变化不大,其破坏面可以用Mises准则描述；结构性较弱时,粘聚力贡献较小或近于丧失,土的强度主要受颗粒摩擦特性的控制,其强度破坏面可以用Mohr-coulomb准则描述。随着结构性的增大,强度破坏面逐渐向外扩展。第五,分析了结构性土准先期固结压力、压缩曲线直线段斜率和回弹段斜率与结构性参数之间的关系。在剖析等结构性条件下土的临界状态力学特性和剑桥模型的基础上,结合土结构性的变化规律和结构性土的强度变形规律,建立了结构性土的弹塑性模型。模型引入了随结构性变化的压缩特性和临界状态线,能够合理的反映结构性土的变形特性。由分析可知,剑桥模型只是该模型在结构性参数等于1时的特殊情况。更多还原

【Abstract】 Structure characteristic is the essential property of natural soils. That it is complicated in qualitative and quantitative makes the study in the "each airs his own views" groping moment.In this paper,based on known research of soil structure and its mechanic effect,the change law of structure property and its strength or deformation constitutive relations have been studied by new true tri-axial apparatus in the theory of comprehensive structure potential.The results are as follows:Firstly,the new true tri-axial apparatus has been debugged and perfected that it was developed by xi’an university of technology. Some key technical problems have been amended,for example, leakage of hydraulic pressure bursa, control of drainage,analysis of apparatus system error, design of accessorial equipments,and so on.In the mean time,the test methods have been summarized detailedly and the limitation of true tri-axial apparatus has been put forward.Secondly,the stress-strain characteristic of intact loess,remolded loess,saturated loess have been researched by tri-axial apparatus.A new structure parameter which is stress ratio structure parameter was proposed that it can reflect the coupling action of shear stress and mean spherical stress.The change law of structure property has been analysed and the relationships between structure parameter and shear deformation,water content, consolidation pressure, stress path have been recognized systemically. The four kinds of failure formation of sample was advanced in true tri-axial condition.Thirdly, based on the relation between strength and structure property,a new strength criterion that it can consider structure property has been proposed and the relations between cohesion force or internal friction angle and structure parameter have been established. It is shown that the structure parameter ratio is in direct proportion to strength ratio.The relation between structure parameter and cohesion can be described as hyperbola.When the soil structure have been destroyed completely,the cohesion is equal to O.The internal friction angle is invariable.Fourthly, The relations between the size or shape of failure surface and structure property have been discussed.The stronger the structure property is, the more the contribution of cohesion force to strength is.So,the strength is equivalent in the condition of tri-axial compress and extrusion.The strength failure surface can be described by Mises criterion for strong structure property soils.When the structure property is weak, the contribution of cohesion force to strength is small and the strength failure surface can be described by Mohr-coulomb criterion.The strength failure surface would be expanded as the increasing of structure parameter.Fifthly,Some new relations have been proposed that it includes qusi-pre-consolidation pressure,the linear moment and rebound slopes of condensation curves with structure parameter.The elastic-plastic models of structured soils have been established combining the change law of strength and deformation based on the analysis of the critical state property for structured soils under the condition of same structure parameter and Cambridge Clay model. The new models introduced a critical state line which moves based on structure parameter,and which can reflect deformation characteristic of structure soils rationally.The Cambridge Clay model is special one of the new model when structure parameter is equal to 1.The research was supported by china natural science fund "Research on Strength and Deformation Theory of Structured Soils Based on Comprehensive Structure Potential" (No.10872161).更多还原