膨胀土膨胀性与收缩性的对比试验研究

发布时间：2018-12-18 05:32

【摘要】：膨胀和收缩是膨胀土最为显著的特性,目前关于膨胀土胀缩性质的联系对比研究较少,大部分文献都是侧重于研究膨胀土的膨胀(或收缩)单方面,此外工程设计中较多考虑膨胀土的膨胀性质,而常常忽视收缩性质。因此对膨胀土的胀缩机理及两者间的联系对比研究显得十分必要。结合理论分析,推导得出膨胀土的膨胀和收缩相关方程。通过一系列室内试验研究,阐明了膨胀土吸水膨胀和失水收缩过程及与之相关的一些规律。最后综合对比膨胀土膨胀和收缩特性,揭示了两者之间的内在统一性和差异性,且阐述了各自的工程意义。首先,理论分析部分主要从膨胀(收缩)过程和膨胀(收缩)方程方面进行论述。膨胀过程主要包括孔隙填充和颗粒膨胀两大阶段,以“粒间膨胀(双电层)”和“晶格膨胀”为理论基础建立了膨胀土理论膨胀方程；收缩过程主要涉及到水分蒸发,水分迁移及裂隙产生等阶段,通过对既有收缩曲线分析得出了收缩经验方程,并指出了产生收缩的细观层面的动力来源于液桥力,宏观层面表现为基质吸力。其次,室内试验主要包括基本土工试验,膨胀试验和收缩试验,各试验均揭示了膨胀土胀缩的相关规律。膨胀试验表明：膨胀土膨胀过程在膨胀时程曲线上可分为快速膨胀,减速膨胀和缓慢膨胀三个阶段。试样最大膨胀率(力)随着初始含水率的增大而逐渐减小,试样最大膨胀力随着初始干密度的增大而逐渐增大。膨胀土吸水膨胀全过程分为“孔隙填充”和“颗粒膨胀”两个阶段,而“颗粒膨胀”又可细划为“吸水阶段-膨胀阶段-稳定阶段”,并得出了膨胀土吸水膨胀方程。收缩试验表明：土中水分蒸发过程在收缩时程曲线上可分为快速蒸发、减速蒸发和缓慢蒸发三个阶段,且膨胀土最大线缩率随着试样初始含水率的增大而递增。膨胀土的收缩全过程可分为“快速收缩、减速收缩、残余收缩”三阶段,其中“快速收缩阶段”主要是孔隙水的流失,“减速收缩阶段”主要是残留孔隙水和弱结合水的散失,“残余收缩阶段”主要为水汽扩散。导致土体产生收缩动力为基质吸力,试验测得其最大值近1MPa。室内试验采用成都和潍坊地区两种膨胀土进行测试,两种土试验结果基本一致。最后,通过对比膨胀土膨胀和收缩特性,得出两者之间的统一性在于本质上都是由水分变化引起的土体结构的改变,并利用这一观点得出了膨胀土保湿法的平衡含水量。膨胀土膨胀性和收缩性之间的差异性主要集中于水的状态、水的运动方向、土体结构改造和土体强度改变等方面,通过差异性对比可解释膨胀土边坡的变形破坏机理。
[Abstract]:Expansion and shrinkage are the most obvious characteristics of expansive soil. At present, there are few relative studies on swelling and shrinkage properties of expansive soil. Most of the literature focuses on the expansion (or contraction) of expansive soil. In addition, the expansive property of expansive soil is considered in engineering design, but the shrinkage property is often neglected. Therefore, it is necessary to study the swelling and shrinkage mechanism of expansive soil and the relationship between them. Based on the theoretical analysis, the expansion and shrinkage equations of expansive soil are derived. Through a series of laboratory experiments, the process of water absorption, water loss and shrinkage of expansive soil and some related laws are expounded. Finally, by comparing the expansion and shrinkage characteristics of expansive soil, the inherent unity and difference between them are revealed, and their engineering significance is expounded. First of all, the theoretical analysis mainly discusses the process of expansion (contraction) and the equation of expansion (contraction). The expansion process mainly includes two stages of pore filling and particle expansion. Based on the theory of "intergranular expansion (double electric layer)" and "lattice expansion", the theoretical expansion equation of expansive soil is established. The shrinkage process is mainly related to the stages of water evaporation, water migration and the formation of cracks. Through the analysis of the existing shrinkage curves, the shrinkage empirical equation is obtained, and it is pointed out that the dynamic force of the meso-plane that produces the shrinkage comes from the liquid bridge force. Macro-level performance for the matrix suction. Secondly, the laboratory tests mainly include basic geotechnical test, expansion test and shrinkage test, and each test reveals the relevant laws of dilatation and shrinkage of expansive soil. The expansion test shows that the swelling process of expansive soil can be divided into three stages: rapid expansion, slow expansion and slow expansion. The maximum expansion rate (force) of the specimen decreases with the increase of the initial moisture content, and the maximum expansion force increases with the increase of the initial dry density. The whole process of water absorption and expansion of expansive soil can be divided into two stages: "pore filling" and "particle expansion", and "particle expansion" can be classified into "water absorption stage, expansion stage-stable stage", and the water absorption expansion equation of expansive soil is obtained. The shrinkage test shows that the process of water evaporation in soil can be divided into three stages: rapid evaporation, deceleration evaporation and slow evaporation, and the maximum linear shrinkage of expansive soil increases with the increase of the initial moisture content of the sample. The whole process of shrinkage of expansive soil can be divided into three stages: rapid shrinkage, deceleration shrinkage and residual shrinkage, in which the "rapid shrinkage stage" is mainly the loss of pore water, and the "deceleration shrinkage stage" is mainly the loss of residual pore water and weakly combined water. The residual contraction stage is mainly water vapor diffusion. The shrinkage force of soil is matrix suction, and the maximum value is about 1 MPA. Two kinds of expansive soils were tested in Chengdu and Weifang, and the results were consistent. Finally, by comparing the expansion and shrinkage characteristics of expansive soil, it is concluded that the unity between the two is essentially the change of soil structure caused by water change, and the equilibrium moisture content of expansive soil is obtained by using this viewpoint. The difference between expansion and shrinkage of expansive soil is mainly focused on the state of water, the direction of water movement, the transformation of soil structure and the change of soil strength, etc. The deformation and failure mechanism of expansive soil slope can be explained by comparing the differences.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU443

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