砂砾覆盖层截留降雨的机理研究

发布时间：2018-01-28 08:02

本文关键词： 砂砾覆盖层入渗产流蒸发截留降雨计算模型　出处：《中国科学院研究生院(教育部水土保持与生态环境研究中心)》2016年博士论文　论文类型：学位论文

【摘要】：砂砾层覆盖于土壤表面,具有抑制土壤水分蒸发、抵抗土壤侵蚀的作用。砂田作为一种旱作覆盖技术,长期应用于我国西北干旱半干旱地区,具有明显调节农田微环境的效果。相关研究具有理论与实用价值。降雨过程中,雨水穿过覆盖层砂砾颗粒间的空隙下落至土壤表面并渗入土壤,其中部分雨水会被砂砾覆盖层截留。本项研究根据颗粒物质物理与力学、材料学和统计学理论,构建了均一和非均一砂砾覆盖层截留降雨量的计算模型。通过模拟降雨测定砂砾覆盖层截留量的实验验证了模型的有效性。本研究取得的主要结果包括:(1)对于均一砂砾覆盖层,可采用平均等效粒径表征其颗粒特征。形状、大小各异的颗粒构成的群体,具有一定自相似特征,可以用分形维数来表征;如土粒质地情况就可以细度分形维数来表征。但由于砂砾级配中往往存在某一粒级(较小的粒级)范围内的质量为零情况,零的对数不存在,以致不能确定其分形维数,因而不能用分形维数表征覆盖层砂砾的颗粒特征。(2)对于非均一砂砾,根据筛分析法的实验结果可求得非均一砂砾试样的总体等效平均粒径。确定了总体等效平均粒径作为表征非均一粒径砂砾试样的技术指标。(3)砂砾层持水量可分为动态持水量和静态持水量。在降雨过程中,覆盖层中砂砾颗粒间空隙中流动的水体,会因降雨不断地流入覆盖层而被更新;这部分只在降雨过程中存在于砂砾覆盖层中的水量称为动态持水量。动态持水过程比较复杂,试图用模型定量描述其过程或计算其技术指标比较困难。降雨停止后,砂砾覆盖层中滞留的雨水经过一段时间的排滴过程,当不再有水体下流时,被截持在砂砾覆盖层中的水量称为静态持水量。静态持水量是降雨后实际被截留在覆盖层中雨水量。(4)根据对均一砂砾覆盖层物理特性的分析,提出了确定均一砂砾覆盖层的最大静截留水量的计算方法。用模拟降雨实验检测结果对模型计算结果进行Paired-Samples T Test过程双侧检验,结果显示,模型计算结果与实验检测的结果差异无显著性。(5)根据对非均一粒径砂砾的级配特征的分析,提出了确定非均一粒径砂砾覆盖层截留雨水量的计算方法。将模型的计算结果与实验检测结果进行Paired-Samples T Test过程双侧检验,结果表明,模型计算和实验检测的结果无显著性差异。本项研究所确定的砂砾覆盖层最大静截留水量的计算模型,是建立在覆盖层技术特征分析基础上的半理论半经验模型。模型考虑了水与砂砾间的物理作用,较统计模型具有更广泛的通用性和更明确的物理意义。研究结果可以用于定量预测砂砾覆盖层截留降雨量的大小。
[Abstract]:Sand and gravel cover the soil surface, which can inhibit the evaporation of soil moisture and resist soil erosion. As a kind of dry mulching technology, sand field has been used in arid and semi-arid areas of northwest China for a long time. It has obvious effect of adjusting farmland microenvironment. Related research has theoretical and practical value. During rainfall, Rain Water falls to the soil surface through the gap between sand and gravel particles in the overburden and seeps into the soil. Some of Rain Water was intercepted by sand and gravel covering. This study was based on particle matter physics and mechanics, materials and statistical theory. The calculation model of rainfall interception in homogeneous and heterogeneous sand gravel cover is constructed. The validity of the model is verified by the experiment of simulated rainfall. The main results obtained in this study include: 1). For homogeneous gravel cover. The average equivalent particle size can be used to characterize the particle characteristics. The population with different shapes and sizes has some self-similar characteristics, which can be characterized by fractal dimension. For example, the grain texture can be characterized by fineness fractal dimension, but the logarithm of zero does not exist due to the fact that there is always zero mass in a certain grain-grade (smaller grain-grade) in the gradation of sand and gravel. As a result, the fractal dimension can not be determined, so the fractal dimension can not be used to characterize the grain characteristics of the covered sand gravel. According to the experimental results of sieve analysis method, the total equivalent average particle size of heterogeneous sand gravel samples can be obtained, and the total equivalent average particle size is determined as the technical index to characterize the heterogeneous gravelly samples. The water holding capacity of gravel layer can be divided into dynamic water holding capacity and static water holding capacity. The water body flowing in the gap between sand and gravel particles in the overburden will be renewed because of the continuous rainfall flowing into the overburden. This part is called dynamic water holding capacity which only exists in the sand gravel cover layer during rainfall. The dynamic water holding process is more complex. It is difficult to quantitatively describe the process or calculate the technical index by using the model. After the rainfall stops, Rain Water in the sand gravel overburden passes through a period of time to discharge the droplet, when there is no water body downflow. The water quantity intercepted in the sand gravel cover is called static water holding capacity. The static water holding capacity is the amount of rain water that is actually retained in the cover layer after rainfall. (4) based on the analysis of the physical characteristics of the uniform sand gravel cover layer, the static water holding capacity is called static water holding capacity. A calculation method for determining the maximum static retention water of homogeneous gravel overburden is proposed. Paired-Samples T is used to calculate the model result with the result of simulated rainfall experiment. Bilateral test of Test procedure. The results show that there is no significant difference between the calculated results of the model and the experimental results. 5) based on the analysis of the gradation characteristics of heterogeneous grained gravel. A calculation method for determining the amount of rainfall interception in non-uniform gravelly covering layer is proposed. The calculated results of the model and the experimental results are applied to Paired-Samples T. Bilateral test of Test procedure. The results show that there is no significant difference between the results of model calculation and experimental detection. It is a semi-theoretical semi-empirical model based on the analysis of the technical characteristics of the overburden. The model takes into account the physical interaction between water and sand and gravel. Compared with the statistical model, the results can be used to quantitatively predict the amount of retained rainfall in sandy gravel cover.
【学位授予单位】：中国科学院研究生院(教育部水土保持与生态环境研究中心)
【学位级别】：博士
【学位授予年份】：2016
【分类号】：S157

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