【作者】 骆亚生；

【导师】 谢定义；

【作者基本信息】 西安理工大学 ， 岩土工程， 2005， 博士

【摘要】 土结构性本构关系的研究被称为是“21世纪土力学的核心问题”。在阅读和分析大量文献资料的基础上,总结了近年来黄土力学研究在非饱和土、动力特性以及结构性等领域取得的丰硕成果,提出了本文研究的基本任务。 本文研究工作的第一个成果是紧密围绕着土结构性形成变化的机理,突出了土结构性研究的土力学途径,把复杂应力条件下的土结构性定量化描述及其应用作为“突破口”,由“土的强度和变形受结构性控制的规律是相同的”这一结论出发,将文献中基于压缩变形考虑的土结构性参数的思路和方法进行了新的发展,提出和定义了基于强度考虑的土结构性定量化参数。这种新的强度型结构性参数,不仅弥补了文献中变形型结构性参数的不足,而且为在静力和动力作用的复杂应力条件下研究土的结构性变化特性和建立结构性本构关系打下了基础。它起到了既继承前人成果的合理内核,又拓展土结构性参数的应用空间,使动、静变形全过程中土结构性变化研究相沟通的重要作用。 本文的第二个成果是对原状的、重塑的和人工结构性的非饱和黄土在侧限压缩应力、常规三轴应力以及真三轴应力条件下进行了大量试验,研究了结构性变化特性,分析了影响黄土结构性的主要相关因素,合理解释了不同试验条件下土结构性参数曲线所表现出的有关特征,论证了新结构性参数的合理性。 本文的第三个成果是首次对原状的和重塑的非饱和黄土进行了大量的动扭剪三人bstr肠Ct轴试验,在动荷作用下分析了非饱和黄土的动力特性,尤其是非饱和黄土孔隙水压力和孔隙气压力在动荷作用下的变化规律,得到了非饱和黄土在动力试验条件下的土结构性参数曲线,证明了非饱和黄土动荷作用‘F的结构性参数曲线与静荷作用下的结构性参数曲线有着相似的形态和变化规律,受相同结构性因素的影响,使结构性定量化参数第一次走进了土动力学研究的领域。 本文的第四个成果是在以上研究的基础上,通过结构性参数对非饱和黄土静、动应力应变关系曲线的归一化作用效果分析,揭示了它与土变形和强度特性密切而规律性的关系,提出了非饱和黄土在静、动力作用的复杂应力条件下结构性的本构关系,验证了它们分别在三轴应力条件和动扭剪应力条件下计算与试验结果间良好的一致性。而且,新的结构性本构关系在静、动力条件下分别具有邓肯一张模型和哈丁模型相似的基本形态及对应的参数,便于在实际工程中应用. 本文的上述研究成果从原则上分析应该对其他土类的结构性研究有重要的借鉴作用,有利于推动土结构性研究从定性到定量,从简单应力条件到复杂应力条件,从试验室研究到实际工程应用的迅速发展.关键词:非饱和黄土结构性变化规律复杂应力条件本构关系更多还原

【Abstract】 The study of structural constitutive relation of soils is called as "the focus problem of soil mechanics in the 21st century". In this paper, based on the observation and analysis of a large number of literature references, the generous outcomes of study on mechanics properties of loess, obtained in resent years are summarized at following areas of unsaturated soil and dynamic characteristics as well as structural characteristics, and the essential duties of this paper are presented. From the works in this paper, some outcomes are obtained as following:Firstly, with the close consideration of mechanism of forming and changing on soil structure and the soil mechanics approach on study of soil structure, the soil structure quantification description and application is taken as "the breakthrough". From the conclusion of "the regularity is same at strength and deformation of soil and is controlled by structure", the conception and method based on compressive deformation indicated in literature are developed, and a new soil structure quantification parameter is presented and defined based on soil strength. This new soil structural parameter not only makes up for the short of the deformation type soil structural parameter indicated in literature, but also makes foundation for the studying soil structural variation characteristics and establishing the structural constitutive relation under static and dynamic complex stress conditions. Its important impact shows as following aspects: to inherit the reasonable core of pre-outcomes, and to develop the application space of soil structural parameter, as well as to connect the study of soil structural variation both in full-process under the deformation of static and dynamic states.Secondly, based on a lot of test carried through for unsaturated loess(such as intact loess, disturbed loess and men-made structural loess) under the conditions of confined compression stress and routine triaxial stress as well as real triaxial stress, the variation characteristics of soil structure are studied under different tests conditions, and the principalcorrelation factors influencing the loess structure are analyzed, the concerned characters put up in the curves of soil structural parameter are interpreted responsibly, and the rationality of new structural parameter is demonstrated forth more.Thirdly, a lot of dynamic torsional shear test are put up for unsaturated loess under its intact and disturbed states respectively, and dynamic characteristics (especially the variation regularity of pore water pressure and pore air pressure) of unsaturated loess are analyzed under action of dynamic load for the first time. Based on the curves of structural parameter for unsaturated loess, obtained under condition of dynamic test, the viewpoint that similar shape and variation regularity exits in curves of structural parameter of unsaturated loess under the actions of static and dynamic load and these are influenced by same factors of structure is proved. This makes the study of soil structure quantification parameter going into the area of soil dynamic mechanics for the first time.Fourthly, based on the above researches, from the impact analyses of normalization action to the static and dynamic stress-strain relations on unsaturated loess impacted, the oscillatory and regular relations between structural parameter and the deformation-strength characters are opened out, and the structural constitutive relations of unsaturated loess are put forward for static and dynamic complex stress conditions, as well as the upstanding consistency between the results of calculation and tests are validated respectively under conditions of triaxial stress and dynamic torsional shear stress. It is shown that the new structural constitutive relations have the similar basic shape of Ducan-Chang model and Hardin model and their corresponding parameters respectively under the static and dynamic conditions, and they can easily be applied to engineering practice.From the analysis in principle, the research results in this paper更多还原