膨胀土干燥收缩特性试验研究
发布时间：2019-01-06 13:32
【摘要】：膨胀土是一种遇水膨胀,失水收缩的特殊土体,对工程结构安全有非常重要的影响。近年来,国内外关注比较多的是膨胀土在遇水或湿化时的膨胀变形特征,而对膨胀土在失水或干燥时的收缩变形特征没有给予足够的关注。但在实际工程中,由膨胀土收缩导致的工程地质问题和灾害时有报道,并产生巨大经济损失。因此,系统掌握膨胀土在干燥失水过程中的体积变化规律,对于指导膨胀土地区的防灾减灾具有重要的理论意义和工程意义。 本文以优秀青年科学基金(41322019)和江苏省自然科学基金(BK2011339)项目为依托,以膨胀土为研究对象,对比分析了不同收缩体积测量方法的优缺点,通过开展大量室内试验,系统研究了膨胀土失水干燥过程中的体积收缩特性及其影响因素和抑制技术,探索了膨胀土干燥收缩过程中主要力学性质的演变规律,在对试验结果进行理论分析的基础上提出了膨胀土收缩模型。论文主要取得以下成果： 1.分析对比了当前四大主要土体收缩体积测量方法,即直接测量法、间接测量法、数字图像处理技术和激光扫描成像法,指出了各个方法的优缺点和适用条件； 2.基于收缩特征曲线,研究了土质成分、含砂量和初始压实状态(含水率和干密度)三个因素对膨胀土在干燥过程中收缩特性的影响,采用控制变量法,掌握了各个影响因素对膨胀土收缩特征的影响规律,明确了其影响机理； 3.提出了膨胀土收缩抑制技术,包括石灰改性技术、水泥改性技术和高分子固化剂改性技术；通过开展大量的室内试验,并结合理论分析,掌握了各技术对膨胀土收缩变形的抑制效果和机理； 4.发现了膨胀土收缩存在显著的各向异性现象,通过引入收缩几何因子r,对膨胀土收缩各向异性进行了定量描述,明确了土质成分、含砂量和含水率等因素对膨胀土收缩各向异性的影响规律； 5.基于大量的室内收缩试验数据,提出一个二次多项式模型来描述膨胀土收缩过程中孔隙比和含水率的变化关系,发现该模型对浦口膨胀土的拟合效果最好,其次为高庙子膨润土和Romainville膨胀土； 6.通过开展无侧限抗压和单轴抗拉试验,研究了膨胀土干燥收缩过程中无侧限抗压强度和抗拉强度随含水率的变化规律,发现：在膨胀土干燥过程中,随着含水率的减少,土体的无侧限抗压强度和抗拉强度都不断增大,且增加速率也不断变大；无侧限抗压强度和抗拉强度随含水率的减小都呈指数增加,且两者具有线性关系；不同初始含水率的膨胀土在干燥到相同含水率时对应的抗拉强度随着初始含水率的增加而增加。
[Abstract]:Expansive soil is a special soil with water expansion and loss of water, which has a very important effect on the safety of engineering structure. In recent years, much attention has been paid to the characteristics of swelling deformation of expansive soil in water or wetting, but insufficient attention has been paid to the shrinkage and deformation of expansive soil during water loss or drying. However, the engineering geological problems and disasters caused by the shrinkage of expansive soil have been reported in the actual engineering, resulting in huge economic losses. Therefore, it is of great theoretical and engineering significance to systematically grasp the law of volume change of expansive soil in the process of drying and losing water, which is of great theoretical and engineering significance for guiding disaster prevention and mitigation in expansive soil area. Based on the excellent Youth Science Foundation (41322019) and the Natural Science Foundation of Jiangsu Province (BK2011339), and taking expansive soil as the research object, this paper compares and analyzes the advantages and disadvantages of different shrinkage volume measurement methods, and carries out a large number of indoor tests. The volume shrinkage characteristics of expansive soil during dehydration and its influencing factors and inhibition techniques are studied systematically. The evolution law of main mechanical properties in the drying process of expansive soil is explored. Based on the theoretical analysis of the experimental results, a shrinkage model of expansive soil is proposed. The main achievements are as follows: 1. This paper analyzes and compares the four main measuring methods of soil shrinkage volume, that is, direct measurement, indirect measurement, digital image processing and laser scanning imaging, and points out the advantages and disadvantages and applicable conditions of each method. 2. Based on the shrinkage characteristic curve, the effects of soil composition, sand content and initial compaction state (moisture content and dry density) on the shrinkage characteristics of expansive soil during drying were studied. The effects of various factors on the shrinkage characteristics of expansive soils are studied, and the mechanism is clarified. 3. The shrinkage inhibition technology of expansive soil was put forward, including lime modification, cement modification and polymer curing agent modification. Through a large number of laboratory tests and theoretical analysis, the inhibition effect and mechanism of various techniques on shrinkage and deformation of expansive soil are grasped. 4. It is found that the shrinkage of expansive soil has obvious anisotropy phenomenon. The shrinkage anisotropy of expansive soil is quantitatively described by introducing the shrinkage geometry factor r, and the soil composition is clarified. The effect of sand content and moisture content on shrinkage anisotropy of expansive soil; 5. Based on a large number of indoor shrinkage test data, a quadratic polynomial model is proposed to describe the relationship between porosity and water content in the shrinkage process of expansive soil. It is found that the model has the best fitting effect on Pukou expansive soil. Secondly, Gaomiaozi bentonite and Romainville expansive soil; 6. By carrying out unconfined compression and uniaxial tensile tests, the variation of unconfined compressive strength and tensile strength with moisture content during drying shrinkage of expansive soil is studied. It is found that the moisture content decreases with the decrease of moisture content in the drying process of expansive soil. The unconfined compressive strength and tensile strength of soil are increasing, and the increasing rate is also increasing. The unconfined compressive strength and tensile strength increase exponentially with the decrease of moisture content, and they have a linear relationship. The tensile strength of expansive soil with different initial moisture content increases with the increase of initial moisture content when drying to the same moisture content.
【学位授予单位】：南京大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU443;TU411
[Abstract]:Expansive soil is a special soil with water expansion and loss of water, which has a very important effect on the safety of engineering structure. In recent years, much attention has been paid to the characteristics of swelling deformation of expansive soil in water or wetting, but insufficient attention has been paid to the shrinkage and deformation of expansive soil during water loss or drying. However, the engineering geological problems and disasters caused by the shrinkage of expansive soil have been reported in the actual engineering, resulting in huge economic losses. Therefore, it is of great theoretical and engineering significance to systematically grasp the law of volume change of expansive soil in the process of drying and losing water, which is of great theoretical and engineering significance for guiding disaster prevention and mitigation in expansive soil area. Based on the excellent Youth Science Foundation (41322019) and the Natural Science Foundation of Jiangsu Province (BK2011339), and taking expansive soil as the research object, this paper compares and analyzes the advantages and disadvantages of different shrinkage volume measurement methods, and carries out a large number of indoor tests. The volume shrinkage characteristics of expansive soil during dehydration and its influencing factors and inhibition techniques are studied systematically. The evolution law of main mechanical properties in the drying process of expansive soil is explored. Based on the theoretical analysis of the experimental results, a shrinkage model of expansive soil is proposed. The main achievements are as follows: 1. This paper analyzes and compares the four main measuring methods of soil shrinkage volume, that is, direct measurement, indirect measurement, digital image processing and laser scanning imaging, and points out the advantages and disadvantages and applicable conditions of each method. 2. Based on the shrinkage characteristic curve, the effects of soil composition, sand content and initial compaction state (moisture content and dry density) on the shrinkage characteristics of expansive soil during drying were studied. The effects of various factors on the shrinkage characteristics of expansive soils are studied, and the mechanism is clarified. 3. The shrinkage inhibition technology of expansive soil was put forward, including lime modification, cement modification and polymer curing agent modification. Through a large number of laboratory tests and theoretical analysis, the inhibition effect and mechanism of various techniques on shrinkage and deformation of expansive soil are grasped. 4. It is found that the shrinkage of expansive soil has obvious anisotropy phenomenon. The shrinkage anisotropy of expansive soil is quantitatively described by introducing the shrinkage geometry factor r, and the soil composition is clarified. The effect of sand content and moisture content on shrinkage anisotropy of expansive soil; 5. Based on a large number of indoor shrinkage test data, a quadratic polynomial model is proposed to describe the relationship between porosity and water content in the shrinkage process of expansive soil. It is found that the model has the best fitting effect on Pukou expansive soil. Secondly, Gaomiaozi bentonite and Romainville expansive soil; 6. By carrying out unconfined compression and uniaxial tensile tests, the variation of unconfined compressive strength and tensile strength with moisture content during drying shrinkage of expansive soil is studied. It is found that the moisture content decreases with the decrease of moisture content in the drying process of expansive soil. The unconfined compressive strength and tensile strength of soil are increasing, and the increasing rate is also increasing. The unconfined compressive strength and tensile strength increase exponentially with the decrease of moisture content, and they have a linear relationship. The tensile strength of expansive soil with different initial moisture content increases with the increase of initial moisture content when drying to the same moisture content.
【学位授予单位】：南京大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU443;TU411
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