土壤入渗与优先流测量方法研究

发布时间：2018-03-02 13:40

本文选题：环式入渗仪　切入点：土壤入渗　出处：《中国农业大学》2017年博士论文　论文类型：学位论文

【摘要】：土壤入渗和优先流是降水或灌溉水转化为土壤水或地下水的关键环节,影响着洪水预算、灌溉系统设计与运行、污染物在地表及土壤中的运移过程。准确测量土壤入渗性能与定量区分土壤基质入渗和优先流过程的相关研究与实践具有重要意义。环式入渗仪是应用最为广泛也是最经典的土壤入渗性能测量仪器。本文提出了环式入渗仪测量入渗率的优化算法与改进装置及定量区分土壤基质与优先流过程的方法。主要研究内容如下。本文认为环式入渗仪的入渗率计算方法及安装过程会造成其测量结果偏大,进行室内试验对假设进行验证。提出了土壤入渗性能曲线最优计算方法,即适当长的时间步长和中点赋值方式能够减小时间步长和水位读数误差对入渗率造成的误差,准确测量土壤入渗性能曲线。提出了可剖分入渗仪和土槽,可视化环内部及下部土壤的真实入渗过程。土壤剖切面湿润特征表明打击环式入渗仪入土的过程造成环壁和土壤之间形成缝隙产生优先流,造成初始阶段环内入渗由垂直向下和径向向内的入渗共同构成,因此环式入渗仪测量的初始入渗率偏大。侧向入渗造成稳定入渗阶段的入渗率测量结果偏大。根据Green-Ampt模型和湿润体特征提出入渗率的校正模型。入渗率校正值与垂直一维入渗率基本一致。在此基础上提出表置式入渗仪,即将双环入渗仪直接放置地表进行测量以避免对地表扰动。室内试验和数值模拟均表明表置式入渗仪能准确测量土壤入渗过程(最大误差18.95%)。提出土壤基质入渗过程的测量方法,进而根据土壤总入渗为基质入渗与优先流入渗之和的事实,发展了用土壤总入渗扣除基质入渗测量得到土壤大孔隙优先流的方法,并进行野外试验,研究林地土壤基质入渗和优先流的定量关系。林地优先流的累积入渗量是基质流的2.0～11.8倍,优先流入渗率是基质流入渗率的2.3～10.2倍;优先流是影响林地水文循环过程的主要因素。提出根据两个初始入渗率计算完整入渗过程的数学方法。计算值与传统测量结果的比例系数为1.001～1.050,R~2＞0.95,表明该方法具有很高的测量精度。该方法能将入渗测量时间缩短到30 min以内,提高了测量效率。本研究对提高土壤入渗性能测量准确性、提高测量效率,为水文循环过程、土壤侵蚀、面源污染防控及灌溉系统设计管理提供有效的工具和研究手段。
[Abstract]:Soil infiltration and preferential flow are the key links for the conversion of precipitation or irrigation water to soil water or groundwater, which affect flood budget, design and operation of irrigation system. Accurate measurement of soil infiltration performance and quantitative differentiation of soil matrix infiltration and preferential flow process are of great significance. Ring infiltration instrument is the most widely used. It is also the most classical instrument for measuring soil infiltration performance. In this paper, an optimization algorithm and an improved device for measuring infiltration rate with a ring infiltration meter are proposed, and a method for quantitatively distinguishing soil matrix from preferential flow process is proposed. The main contents of this paper are as follows. In this paper, it is considered that the calculation method and installation process of the infiltration rate of the ring infiltration meter will cause the measurement results to be too large. An optimal calculation method of soil infiltration performance curve is put forward, that is, a proper time step and a midpoint assignment method can reduce the error caused by time step and water level reading error to infiltration rate. The curve of soil infiltration performance was measured accurately. A divisible infiltration instrument and soil trough were proposed. The wetting characteristics of soil profile indicate that the penetration process of punching ring infiltration instrument results in the formation of gap between the ring wall and the soil to produce preferential flow. In the initial stage, the infiltration in the ring is composed of vertical downward infiltration and radial infiltration. Therefore, the initial infiltration rate measured by the loop infiltration meter is larger than that measured by the loop infiltration instrument, and the measurement result of the infiltration rate in the stable infiltration stage is larger due to the lateral infiltration. According to the Green-Ampt model and the wetted body characteristics, the correction model of the infiltration rate is proposed. The vertical one-dimensional infiltration rate is basically the same. In order to avoid surface disturbance, the double ring infiltration instrument is placed directly to avoid surface disturbance. Laboratory tests and numerical simulation show that the surface infiltration instrument can accurately measure soil infiltration process (the maximum error is 18.95 50.The method of measuring soil matrix infiltration process is put forward. According to the fact that the total infiltration of soil is the sum of matrix infiltration and preferential infiltration, the method of subtracting matrix infiltration from soil total infiltration to obtain the soil macroporous preferential flow is developed, and the field test is carried out. The quantitative relationship between soil matrix infiltration and preferential flow in forestland was studied. The cumulative infiltration amount of forestland priority flow was 2.0 ~ 11.8 times as much as that of substrate flow, and the preferential inflow infiltration rate was 2.3 ~ 10.2 times as much as that of substrate flow. Priority flow is the main factor affecting the hydrological cycle process of forestland. A mathematical method for calculating complete infiltration process based on two initial infiltration rates is proposed. The proportional coefficient between the calculated value and the traditional measurement result is 1.001 ~ 1.050 / Rn2 > 0.95. it shows that this method has a very good performance. This method can shorten the time of infiltration measurement to less than 30 min. This study can improve the accuracy and efficiency of soil infiltration measurement, and provide effective tools and research means for hydrological cycle, soil erosion, non-point source pollution prevention and control and irrigation system design and management.
【学位授予单位】：中国农业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：S152.7

【参考文献】