硫酸盐渍土水—盐迁移试验研究

发布时间：2018-08-03 21:42

【摘要】：盐渍土在道路工程中属于性质不良用土,当被用作路基填料时,所填筑路基容易出现溶陷、盐胀、冻胀翻浆等病害,而这些病害产生的根本原因是由于路基中水分和盐分集聚迁移的结果。本文在考虑水分和盐分迁移动力的基础上,设计室内土柱试验探究土体内部水盐迁移特性,分析了不同含水率、不同含盐量的硫酸盐渍土在常温条件、冻融循环条件下的水分、盐分迁移特性。(1)进行了8组不同含盐量的硫酸盐渍土击实试验,研究结果表明:盐渍土击实曲线与素土击实曲线具有相似性,随着含水率增加,干密度呈先增大后减小的趋势;对于不同含盐量的硫酸盐渍土而言,随着含盐量的增加,其最大干密度逐渐减小,最佳含水率逐渐增大。(2)分析了洗盐烘干法、TDR(时域反射测试系统)和ECH2O(电导率测试系统)进行硫酸盐含水率和含盐量测试的优缺点;推荐了ECH2O电导率测试系统为硫酸盐含量和含水率的测试方法。(3)采用滤纸法测定了硫酸盐渍土的土水特征曲线,分析了不同含盐量下基质吸力的大小关系,结果表明,硫酸盐含盐量越高,其基质吸力越大,基质吸力与土体体积含水率呈现指数关系。(4)进行常温下室内土柱水盐迁移试验,对其水分和盐分进行动态监测。对于同一含水率下不同含盐量的盐渍土而言,盐分梯度是水盐迁移的动力;而对于相同含盐量土柱中的水盐迁移,含水率的差别是其迁移的动力来源,且含水率越大迁移越明显。(5)与常温条件下试验结果相比,冻融循环作用对水盐迁移的影响明显,表明温度梯度对水盐迁移的作用效果十分明显,而随着冻融循环次数的增加,顶部水分的累积和盐分的聚集现象越来越显著。(6)基于土体内部水-盐迁移的特性,分析了土体次生盐渍化产生的原因及对路基的病害,在此基础上,归纳了现有次生盐渍化路基病害的防治措施。
[Abstract]:Salinized soil is a kind of bad soil in road engineering. When it is used as filling material of roadbed, the subgrade is liable to dissolving, salt heaving, frost heaving and so on. The root cause of these diseases is the accumulation and migration of water and salt in roadbed. On the basis of considering the power of water and salt migration, the soil column test in the design room explored the characteristics of water and salt migration in soil, and analyzed the moisture of sulphate saline soil with different water content and different salt content under the conditions of freezing and thawing cycle at room temperature. (1) eight groups of sulphate soil compaction tests with different salt contents were carried out. The results showed that the compaction curve of saline soil was similar to that of plain soil, and the dry density increased first and then decreased with the increase of moisture content; For sulphuric acid saline soils with different salinity, the maximum dry density decreases with the increase of salt content. The optimum moisture content increased gradually. (2) the advantages and disadvantages of TDR (time Domain reflection Test system) and ECH2O (conductivity Measurement system) were analyzed. The ECH2O conductivity measurement system is recommended as the test method of sulfate content and moisture content. (3) the soil water characteristic curve of sulphate saline soil is measured by filter paper method, and the relation of matrix suction with different salt content is analyzed. The higher the sulfate salt content, the greater the matrix suction, and the relationship between the matrix suction and soil volume water content was exponential. (4) the indoor soil column water and salt migration tests were carried out at room temperature, and the moisture and salt contents were dynamically monitored. For salinized soil with the same water content, the salt gradient is the driving force of water and salt migration, but for the same salt content soil column, the difference of water content is the driving force of its migration. The larger the moisture content is, the more obvious the migration is. (5) compared with the experimental results at room temperature, the effect of freezing and thawing cycle on water and salt migration is obvious, which indicates that the effect of temperature gradient on water and salt migration is very obvious, but with the increase of freezing and thawing cycle times, The accumulation of water at the top and the accumulation of salt are becoming more and more obvious. (6) based on the characteristics of water-salt migration in soil, the causes of secondary salinization of soil and the disease of subgrade are analyzed. The prevention and cure measures of secondary salinization roadbed diseases are summarized.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U416.1

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