粘土—裂隙间水量交换试验研究

发布时间：2018-03-06 12:47

本文选题：粘土　切入点：裂隙　出处：《哈尔滨工业大学》2015年硕士论文　论文类型：学位论文

【摘要】：裂隙为污染物(或降雨)入渗和土体中水分的蒸发提供了重要的优势通道。裂隙与土体之间水量交换的定义为在渗透和蒸发条件下水在裂隙与土体之间的相互运动,其包括渗透和蒸发两种形式,渗透形式的水量交换是裂隙中优势流的重要形式,以水量交换率进行数学描述。而目前的研究主要针对砂土中的圆柱形裂隙,对于粘土中平板裂隙与粘土间的水量交换率试验研究还处于空白。其主要的难点包括以下两个方面:粘土中的裂隙宽度会随着土体含水量的变化而开裂或者闭合;粘土中的裂隙宽度通常较小。对于蒸发形式的水量交换试验研究,目前研究得到的主要结论是裂隙的存在能够显著增加土体的蒸发量,但对于裂隙如何具体影响土体蒸发的研究还比较少。其主要困难是影响土体蒸发的因素众多,即包括自然因素又包括土体自身因素,因此很难建立一个准确计算单独由裂隙产生的蒸发量的数学模型。本文针对粘土中裂隙的特点设计了一套试验装置,通过含水量传感器和张力计等测量系统,定量地计算了粘土-裂隙间的水量交换率,并得到了粘土-裂隙间的界面渗透系数。同时研究了土体初始含水量和裂隙宽度对渗透形式试验水量交换率的影响。研究发现对于具有不同初始含水量的土体,其水量交换率在渗透初期最大,随着土体中基质吸力的降低而降低,粘土-裂隙间的界面渗透系数比土体的饱和渗透系数大一个数量级。不同裂隙宽度的土体,其水量交换率也是在渗透初期最大,随着土体中基质吸力的降低而降低。粘土与裂隙间的界面渗透系数也比土体的饱和渗透系数大一个数量级。当土体中裂隙宽度不同时,渗透初期不同裂隙宽度土体的水量交换率相差较大,随着渗透的进行,这种差别逐渐变小,最后水量交换率趋于稳定。本文针对含裂隙土体蒸发的特点设计了一套试验装置,通过含水量传感器和张力计测量系统,定量地研究了土体初始含水量和裂隙宽度对土体蒸发量和蒸发过程中裂隙周围土体含水量变化的影响。研究发现对于不同裂隙宽度和不同初始含水量的土体,土体蒸发量在蒸发初期最大,随着蒸发的进行迅速降低,最后趋于稳定。裂隙周围土体的含水量在竖直方向随着土体深度的增加而增加,在同一水平方向随着距裂隙中心距离的增加而增加。土体中裂隙越大,土体的蒸发量也越大,土体初始含水量越接近土体最优含水量,土体的蒸发量越大。
[Abstract]:Fissures provide important superior channels for pollutant (or rainfall) infiltration and evaporation of water in soil. Water exchange between fissure and soil is defined as the movement of water between fissure and soil under permeable and evaporation conditions. The water exchange is an important form of the dominant flow in a fissure, which is described mathematically by the water exchange rate, and the current research is mainly focused on the cylindrical fissure in sand. The experimental study on the water exchange rate between flat fissure and clay in clay is still blank. The main difficulties include the following two aspects: the crack width in clay will crack or close with the change of soil water content; The width of cracks in clay is usually small. For the experimental study of water exchange in the form of evaporation, the main conclusion of the present study is that the existence of cracks can significantly increase the evaporation of soil. However, there are few studies on how cracks affect soil evaporation. The main difficulty is that there are many factors that affect soil evaporation, that is, natural factors as well as soil itself. Therefore, it is difficult to establish a mathematical model to calculate the evaporation produced by cracks alone. In this paper, according to the characteristics of cracks in clay, a set of test equipment is designed, which is measured by water content sensor and tensometer, etc. The water exchange rate between clay and fracture is calculated quantitatively. At the same time, the influence of initial water content and crack width of soil on the water exchange rate of seepage test is studied. It is found that for soil with different initial water content, The water exchange rate of the soil decreases with the decrease of the soil matrix suction. The interfacial permeability coefficient between clay and fracture is one order of magnitude larger than the saturated permeability coefficient of soil. The water exchange rate is the highest in the early stage of infiltration and decreases with the decrease of the suction of the matrix. The interfacial permeability coefficient between clay and fracture is also one order of magnitude larger than the saturated permeability coefficient of soil. When the width of fracture in soil is different, The water exchange rate of soil with different fracture width is quite different in the early stage of permeability, and the difference becomes smaller gradually with the permeation, and the water exchange rate tends to be stable at the end. A set of experimental equipment is designed in this paper according to the characteristics of evaporation of fissured soil. Through the water content sensor and the tensometer measuring system, The effects of initial water content and crack width on soil evaporation and soil moisture content in the process of evaporation are quantitatively studied. The soil evaporation is the largest in the initial stage of evaporation, and decreases rapidly with the evaporation, and finally tends to stabilize. The water content of the soil around the fracture increases in the vertical direction with the increase of soil depth. In the same horizontal direction, with the increase of distance from the crack center, the larger the fissure, the larger the soil evaporation, the closer the soil initial water content is to the optimum soil water content, and the larger the soil evaporation is.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X141;TU41

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