吉林省西部地区盐渍土水分迁移及路基处理措施研究

发布时间：2018-03-04 15:37

本文选题：盐渍土　切入点：水分迁移　出处：《长春工程学院》2017年硕士论文　论文类型：学位论文

【摘要】：吉林省西部地区地处我国松嫩平原西南部,是我国土地盐碱化较为严重的地区之一,属于东北典型的季节性冻土区。季节性冻土是一种由土颗粒、液态水、冰、气态水组成的四相地质体。土壤发生冻结时,土壤中的水分和盐分均发生运移,会在农牧业、环境、水资源、基础工程等方面引发不同程度的病害,盐胀、冻胀及翻浆等会导致路基开裂、隆起、膨胀,从而降低了路基的稳定性和强度。土壤中水盐的运移是导致该地区盐渍化加剧的重要原因,水盐运移的研究越来越受到人们的关注,该研究不仅有助于促进非饱和土体水分迁移理论研究的进展,而且为冬季出现的不同程度的冻胀破坏现象以及道路病害治理提供理论依据和技术支持,对治理土地盐碱化、防止农业生态系统退化等具有重要理论价值。本文以吉林省农安县盐渍土为试验研究对象,对研究区土样的物质组成和基本理化性质进行试验分析,然后进行室内直接法和温度梯度冻结法水分迁移试验。结合水、热、盐运移之间的相互联系,参考以往研究取得的理论成果并结合能量守恒方程、质量守恒方程等建立冻结条件下盐渍土水、热、盐运移耦合数学模型。采用有限元法对模型进行求解,将求解结果与室内试验结果相对比,以此验证模型的有效性。主要研究成果有:1.土壤中的粒度成分以粉粒和粘粒为主,矿物成分有大量原生矿物和少量次生矿物,各深度土体的天然密度基本维持在1.91g/cm3左右,易溶盐总量随深度的增加而减小,其中表层易溶盐总量含量最高为1.69%,土壤中的盐分组成以Na2CO3和NaHCO3为主,土体为弱碳酸盐渍土。2.直接法毛细水上升试验结果表明在室温状态下毛细水上升的高度是很小的,并且土体压实度越大毛细水上升高度越低。温度梯度冻结法水分迁移试验结果表明在冻结状态下土体中水分和盐分均发生了运移,温度梯度致使土体中结合水发生运移而并非毛细水,盐分的运移以水分为载体,受温度势、溶质势等多种因素影响,并且土体压实度越大水分和盐分的运移量越少。3.冻结条件下,盐渍土系统中任意一点的水分、热量、溶质的运移都是相互联系、相互影响、相互作用的,形成了一个复杂的水、热、盐运移耦合系统。所建模型求解结果与试验结果吻合度较好,说明模型能较好的模拟实际情况。4.依托工程实例,根据处理原理,结合盐渍土水盐迁移规律及地下水文条件,就路基提出了相关处理措施,预防盐渍土地区公路路基病害的发生。
[Abstract]:The western region of Jilin Province is located in the southwest of Songnen Plain in China. It is one of the most serious salinization areas in China and belongs to the typical seasonal frozen soil region in Northeast China. Seasonal frozen soil is a kind of soil particle, liquid water and ice. A four-phase geological body composed of gaseous water. When the soil freezes, both the water and salt in the soil migrate, which will lead to different degrees of disease and salt swelling in agriculture, animal husbandry, environment, water resources, basic engineering, etc. Frost heaving and mudding will lead to the cracking, uplift and expansion of the roadbed, thus reducing the stability and strength of the roadbed. The migration of water and salt in the soil is an important reason for the increase of salinization in this area. More and more attention has been paid to the study of water and salt migration, which is not only helpful to promote the research progress of unsaturated soil water migration theory. It also provides theoretical basis and technical support for different degrees of frost heaving and road disease treatment in winter, and it can control the salinization of land. It is of great theoretical value to prevent the degradation of agricultural ecosystem. In this paper, the material composition and basic physical and chemical properties of soil samples in Nong'an County of Jilin Province are studied. Then the indoor direct method and the temperature gradient freezing method were used to test the water migration. Considering the interrelation of water, heat and salt migration, and referring to the theoretical results obtained from previous studies and the energy conservation equation, The coupled mathematical model of water, heat and salt migration in saline soil under freezing condition was established by mass conservation equation. The finite element method was used to solve the model, and the results were compared with the results of laboratory tests. The main results of this study are as follows: 1. The particle size components in the soil are mainly silt and clay, and the mineral composition has a large number of primary minerals and a small amount of secondary minerals, and the natural density of each depth of soil is maintained at about 1.91 g / cm ~ 3, and the natural density of the soil is about 1.91 g / cm ~ 3. The total content of soluble salt decreased with the increase of depth. The content of soluble salt in surface layer was the highest, and the salt composition in soil was mainly Na2CO3 and NaHCO3. The results of direct capillary water rising test show that the height of capillary water rise is very small at room temperature. The higher the compaction degree of soil is, the lower the rising height of capillary water is. The results of water migration test by temperature gradient freezing method show that both moisture and salt in soil are transported under freezing condition. The temperature gradient results in the migration of combined water instead of capillary water in soil, and the migration of salt is divided into water as carrier, which is affected by temperature potential, solute potential and other factors, such as temperature potential, solute potential and so on. And the larger the compactness of soil is, the less the amount of water and salt migration is. 3. Under freezing conditions, the movement of water, heat, solute at any point in the saline soil system is interrelated, interacted, interacted, and formed a complex water. Coupled system of thermal and salt transport. The results of the model are in good agreement with the experimental results, which shows that the model can simulate the actual situation well. 4. Based on engineering examples, according to the principle of treatment, combined with the law of water and salt migration in saline soil and the conditions of groundwater text, In order to prevent highway roadbed disease from occurring in saline soil area, the related treatment measures are put forward in this paper.
【学位授予单位】：长春工程学院
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U416.16

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