摘要
In arid regions, water vapor diffusion predominates the total water migration in unsaturated soil, which significantly influences agriculture and engineering applications. With the aim of revealing the diffusion mechanism of water vapor in unsaturated soil, a water vapor migration test device was developed to conduct the water vapor migration indoor test. The test results demonstrate that the characteristics of water vapor diffusion in unsaturated soil conformed to Fick’s second law. A mathematical model for water vapor diffusion under isothermal conditions in unsaturated soil was established based on Fick’s law. Factors including the initial moisture content gradient, initial moisture content distribution, soil type and temperature that affect the water vapor diffusion coefficient were analyzed. The results show that there was good agreement between the moisture content calculated by the mathematical model and obtained by the indoor experiment. The vapor diffusion coefficient increased with increasing initial moisture content gradient and temperature. When the initial moisture content gradient is constant, the vapor diffusion coefficient increases with the increase of matrix suction ratio in dry and wet soil section. The effect of soil type on the water vapor diffusion coefficient was complex, as both the moisture content and soil particle sizes affected the water vapor diffusion.
干旱地区非饱和土中汽态水扩散是水分迁移的主要组成部分,这对农业和工程应用具有重要影响。为了揭示非饱和土中汽态水扩散机理,研制了汽态水扩散试验装置,进行了非饱和土汽态水扩散室内试验。试验结果表明非饱和土中汽态水扩散特性符合Fick第二定律。基于Fick定律,建立了等温条件下非饱和土汽态水扩散的数学模型,分析了初始含水率梯度、初始含水率分布、土体类型和温度等因素对汽态水扩散系数的影响。结果表明:用所建的数学模型计算的含水率与室内试验结果吻合较好;汽态水扩散系数随着初始含水率梯度和温度的增加而增大;在初始含水率梯度一定的条件下,汽态水系数随着这干土段和湿土段基质吸力比值的增大而增大;含水率和土颗粒粒径均对汽态水扩散系数有所影响,致使土体类型对汽态水扩散系数的影响比较复杂。
基金
Projects(51878064, 51378072) supported by the National Natural Science Foundation of China
Projects(300102218408, 300102219108) supported by the Fundamental Research Funds for the Central Universities, China。
作者简介
Corresponding author:MAO Xue-song,PhD,Professor,Tel:+86-18192830325,E-mail:xuesongxian@aliyun.com,ORCID:0000-0003-2325-7661。
