【作者】 杨震雷；

【导师】 万力；

【作者基本信息】 中国地质大学（北京） ， 地下水科学与工程， 2010， 硕士

【摘要】 非饱和土壤中水汽热运移受到水文学和土壤物理学等学科的深入关注,这一研究对于查明干旱半干旱地区地表和大气间水分和能量的交换过程十分重要。土壤中水热运移方程能够相互耦合主要是水汽运移的结果,所以,这一研究重点就集中在对土壤中各种水汽运移机制的探讨。对于水汽扩散运移机制,国内外学者已经做了许多研究,而对水汽对流和水汽弥散机制的研究相对较少。本文在土壤物理参数试验以及含水量观测仪器EasyAG50温度效应校正试验的基础上,利用采自巴丹吉林沙漠的细砂进行了三种不同条件下的砂箱试验,根据试验结果初步探讨了各种水汽运移机制对土壤含水量变化的影响特征。通过密封恒温试验,得出当采用风干的沙漠细砂进行砂箱水汽热运移试验时,可以忽略液态水运移对土壤含水量的影响。通过密封变温试验,得出土壤含水量在剧烈变温条件下的改变主要是由仪器本身的温度效应引起的,水汽扩散在此阶段不起主要作用;当土壤温度逐渐趋于稳定时,水汽扩散对土壤含水率变化的作用才和温度效应相当,甚至超过温度效应。通过通风变温试验,得出在空气实际平均流速为0.011cm/s的条件下,水汽对流和仪器温度效应对土壤含水量变化的贡献率分别为191.2%和28.6%,而水汽弥散和水汽扩散对土壤含水量改变的贡献率分别为-25.5%和-94.1%。这表明此时,水汽对流是土壤含水量改变的最重要影响因素,而不是通常认为的水汽扩散。更多还原

【Abstract】 Coupled water, water vapor, and heat transport in unsaturated soil has enjoyed intensive focus in hydrology and soil physics. This research plays an important role in identifying water and energy exchange process between land surface and atmosphere in arid and semiarid areas.The coupling of the water and heat transfer equations is mainly resulting from the water vapor movement, therefore, naturally, this area research has focused on each water vapor transport mechanisms in the unsaturated soil. Domestic and foreign scholars have done a lot of research on the water vapor diffusion and yet, pay relatively little attention to the research of water vapor convection and dispersion.Based on the soil physical parameters experiment and calibration experiment of temperature effect of the soil moisture monitoring equipment EasyAG50, this dissertation conducts sandbox experiment under three different conditions, using fine sand which is collected from the Badain Jaran Desert. Meanwhile, according to the experiment results, this dissertation preliminary probes into the impact of each water vapor transport mechanisms on the changes in soil moisture content.Through sandbox experiment under airtight and constant temperature conditions, the author concludes that the effect of liquid water transport on changes in soil moisture content could be ignored when using air-dry desert fine sand in this sandbox experiment.Through sandbox experiment under airtight and fluctuant temperature conditions, the author concludes that the change in soil moisture content under fluctuant temperature condition mainly results from the temperature effect of the equipment EasyAG50 itself, the water vapor diffusion plays a minor role at this stage; and that when the soil temperature gradually stabilizes, the change in soil moisture content chiefly arises from the water vapor diffusion but not the equipment temperature effect. Through sandbox experiment under ventilated and fluctuant temperature conditions, the author concludes that under the actual average air flow rate 0.011cm/s conditions, the contribution rates of water vapor convection and equipment temperature effect on changes in soil moisture content are 191.2% and 28.6% respectively, while the contribution rates of water vapor diffusion and dispersion on changes in soil moisture content are -25.5% and -94.1% respectively. This indicates that under such conditions, water vapor convection is the most important factors to the change in soil moisture content, but not the well-known water vapor diffusion.更多还原