【作者】 董佩；

【导师】 王旭升；

【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】 潜水蒸发是浅层地下水消耗的主要途径,是地下水向土壤水和大气水转化的主要形式,也是四水转化的重要环节。研究潜水蒸发对于探讨四水转化机理、农田灌溉、盐碱地防治以及水资源评价等都有重要的意义。本文结合国家自然基金课题,采用理论分析与室内实验相结合的方法,研究潜水面的动态变化过程,所作研究和初步成果如下:(1)通过参阅国内外文献资料,总结了确定土壤水分特征曲线各种方法的优缺点。在测定地大粗砂的干密度、粒径分布和饱和渗透系数的常规实验的基础上,采用自主设计的砂柱实验这种新型试验方法测定了地大粗砂的土壤水分特征曲线,试验结果显示其呈很好的“S”型曲线。能够利用van-Genuchten模型拟合试验结果,通过与压力膜仪法实测的土壤水分特征曲线的对比分析,指出两种方法确定土壤水分特征曲线的优点和存在的不足之处。相比而言,砂柱实验确定土壤水分特征曲线具有方法简单、精确度高、实验成本低的优势。(2)在分析潜水蒸发影响因素及现有观测方法的基础上,以质量守恒定律为原理,通过初始饱和的砂柱实验,研究不同蒸发历时,潜水蒸发量及潜水蒸发系数随埋深的变化,实验中潜水蒸发主要受到埋深以及大气蒸发能力的影响,随着埋深的增加,大气蒸发能力影响减弱,潜水蒸发量和蒸发系数都会减小。指数公式C= 23.331e-0.8464D可以较好地拟合实测潜水蒸发系数随埋深的变化。(3)以土壤水动力学理论为指导,建立潜水动态蒸发的数学模型,使用Hydrus-1D软件对砂柱动态蒸发实验进行模拟。模型计算的潜水蒸发量和实测的潜水蒸发量除个别观测点处误差较大外,其他各点相对误差较小,其宏观形态拟合效果较好,模型整体上能够较好的模拟潜水动态蒸发的变化过程,数值模拟值与实测值的趋势基本一致,可满足精度的要求。(4)由于受客观条件的限制,实验尚存在一些不足之处需要改进,文中提出了改进的建议。更多还原

【Abstract】 Phreatic evaporation is the main depletion way of shallow groundwater, it is the main form for groundwater to turn into the soil water and atmospheric water and also an important part of transformation in four-water. The study of phreatic is of great importance for four- water transformation mechanism, irrigation, saline control and evaluation of water resources.Surpporting by the National Natural Science Foundation,this paper takes the method of theoretical analysis combining with laboratory to study the dynamic evaporation process of the water table, the research and preliminary results are as follows:(1) By referring internal and external literatures, the paper summarizes the advantages and disadvantages of the methods of determining the soil water characteristic curve. Based on some conventional experiments including density, particle-size distribution, saturated hydraulic conductivity coefficient, we develop a laboratory experiment of sand column to measure the soil water characteristic curve. It turns out that the curve presents“S”well. At the same time, we see that van Genuchten model is able to match the measured moisture-suction data of the sand material used in the experiments well. Furthermore, pressure-membrane apparatus is applied to determine the soil water characteristic curve,from which inherent advantages and deficiencies of the methods are analyzed. Based on the analysis and comparisons, the laboratory experiment of sand column provides great accuracy, low cost, simple operate in determining the soil water characteristic curve.(2) On the basis of analysis of Phreatic evaporation and the existing observation methods ,according to the principle of conservation of mass, By the experiment of initial saturated sand column to study the changes of Phreatic evaporation and the evaporation coefficient with depth in different evaporation duration, Phreatic evaporation in the experiment was mainly influenced by the depth and the aatmospheric evaporation, with the increase of depth,the influence of atmospheric evaporation increases too, Phreatic evaporation and the evaporation coefficient will both decrease. Index formula C = 23.331e-0.8464D can better fit the measured evaporation coefficient changing with depth.(3) To soil water dynamics theory, we established a mathematical model of Phreatic dynamic evaporation,using Hydrus-1D to simulate the dynamic evaporation of the sand column experiments. Except for some specific points, the Model calculation and the measured evaporation have less error,the macroscopic morphology was well fitted ,so the model can better simulate the overall change process of Phreatic dynamic evaporation, the trends of numerical simulation and measured are identical and the requirements of precision can be satisfied.(4) Due to objective conditions, there are still some shortcomings in the experiments needed to be improved, the paper has put forward some suggestions for further improvement.更多还原