土体成分及其分布对土体强度和流变性影响的试验研究

发布时间：2018-07-29 08:27

【摘要】：流变相物质是指吸附在固相颗粒表面的结合水和胶体物质在偏应力或压力差作用下，既可产生变形又可产生流动，，即具有与固体相似的变形性质同时又具有与液体相似的流动性质。土的流变分为流质流变和范性流变，其中流质流变是由流变相物质产生的流变；而范性流变主要是指在剪应力作用下土体固相颗粒之间产生的滑动和蠕动，以及在接触应力（有效应力）作用下引起的固体颗粒表面原子和位错的迁移及扩散而引起的相互滑动和蠕动。一般认为，软土的流变主要属于流质流变，而砂土等粗颗粒土流变主要是在高应力阀值下的范性流变。由此可见，软土的流变机理与砂土的流变机理是不同的。本文的研究工作主要从细观的角度就流变相物质对土体流变性性的影响进行研究，进一步完善流变相这一概念。流变相物质包括通过黏土矿物、有机物和某些氧化物等物质的表面电荷与水产生相互作用而形成的结合水和胶体等具有流变性质的物质以及土体中具有流变性的其它物质。流变相物质是土体流变的物质基础，把土体的流变性质与客观物质对应起来，揭示土的细观结构和土流变性质的内在联系。采用广州河砂、广州粘土、人工土、有机质土等作为研究样本，分析其矿物组成成分及其他细观参数与土体流变性的对应性和相关性。提出土体流变的“四相”理论模型与流变元件，根据模型中不同分布的流变相复合体，制作试样进行流变试验，探究流变相物质的成分含量、形状及分布对土体流变特性的影响。本文开展的研究工作和取得的成果有如下几个方面： (1)研究不同矿物成分和含水量的土体的强度特性。根据试验结果分析，认为矿物颗粒之间的摩擦与胶结粘聚作用是土体强度特性的决定因素。 (2)采用广州河砂、人工土、有机质土等为研究样本，进行直剪蠕变试验并探究了砂性土与软土各自的流变机理。试验结果表明，砂性土的流变通常是在高应力阀值下产生的，而流变物的矿物含量对软土流变性产生不同程度的影响。它们分别属于范性流变和流质流变。 (3)研究流变相物质的形状（如球状、柱状、方形状、网络状等）、分布（如流变物为一个球体、三个球体、五个球体等）及成分比例（如流变物为含5%有机质、10%有机质等）对土体流变性的影响。试验结果表明，流变相物质的含量比例对流变特性影响显著，而其形状及分布的影响随着分布的均匀化（同比例，但尺寸越来越小）而逐步消失，至一定程度（网状分布）流变相物质的形状及分布差异所引起的影响基本消失，此时试样的流变性与流变相物质的形状及分布基本无关，而主要与流变物质的矿物种类及其含量比例有关。 (4)提出了软土的四相组成模型。软土可看成是由固相、液相、气相和流变相四相组成的介质。
[Abstract]:Fluid phase material refers to the combination of water and colloid adsorbed on the surface of solid particles, which can produce both deformation and flow under the action of deviant stress or pressure difference. It has the deformation property similar to the solid and the fluidity similar to the liquid. The rheology of soil can be divided into fluid rheology and normal rheology, in which fluid rheology is produced by fluid rheology, while normal rheology mainly refers to sliding and creeping between solid particles under shear stress. In addition, the migration and diffusion of atoms and dislocations on the surface of solid particles caused by contact stress (effective stress) cause mutual sliding and creep. It is generally believed that the rheology of soft soil is mainly fluid rheology, while the rheology of coarse granular soil such as sand is mainly the normal rheology under high stress threshold. Therefore, the rheological mechanism of soft soil is different from that of sand. In this paper, the effect of fluid phase on rheological properties of soil is studied from the point of view of meso, and the concept of rheological phase is further improved. Fluid phase materials include rheological substances such as water and colloid formed by interaction of surface charge of clay minerals organic compounds and some oxides with water and other substances in soil with rheological properties. Fluid phase material is the material foundation of soil rheology. The rheological property of soil is corresponding to objective material, and the internal relation between soil mesoscopic structure and soil rheological property is revealed. Using Guangzhou River Sand, Guangzhou Clay, artificial soil and Organic soil as the study samples, the correspondence and correlation between the mineral composition and other meso-parameters and the rheological properties of the soil were analyzed. The "four-phase" theoretical model of soil rheology and the rheological elements are proposed. According to the fluid phase complex with different distribution in the model, the rheological tests are carried out to investigate the composition content of the fluid phase material. Effect of shape and distribution on rheological properties of soil. The research work and results obtained in this paper are as follows: (1) the strength characteristics of soils with different mineral composition and water content are studied. According to the analysis of test results, it is considered that friction and cementation between mineral particles are the decisive factors of soil strength. (2) Guangzhou River sand, artificial soil, organic soil and so on are used as the study samples. The direct shear creep test was carried out and the rheological mechanism of sandy soil and soft soil were investigated. The results show that the rheology of sandy soil is usually produced under high stress threshold, and the mineral content of rheological material has different effects on rheological properties of soft soil. They belong to normal rheology and fluid rheology respectively. (3) study the shape (such as globular, columnar, square, network, etc.) of rheological materials, distribution (e.g., rheological material is one sphere, three spheres, etc.), The effects of five spheres and the proportion of components (such as 5% organic matter, 10% organic matter, etc.) on the rheological properties of soil. The results show that the content ratio of fluid phase material has a significant effect on rheological properties, and the influence of its shape and distribution gradually disappears with the homogenization of the distribution (the same proportion, but the size is getting smaller and smaller). To a certain extent, the influence caused by the difference in the shape and distribution of fluid phase material is basically disappeared, and the rheological property of the sample is basically independent of the shape and distribution of the fluid phase material. It is mainly related to the mineral type and content ratio of rheological materials. (4) the four-phase composition model of soft soil is proposed. Soft soil can be regarded as a medium consisting of solid, liquid, gas and fluid phases.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU41

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