【作者】 李红星；

【导师】 樊贵盛；

【作者基本信息】 太原理工大学 ， 环境工程， 2010， 博士

【摘要】 目前,我国农田灌溉仍以传统的地面灌溉为主,由明渠输水的灌溉面积占总灌溉面积的75%以上,每年由灌溉渠道损失的水量为占我国总用水量的33%。据山西省的估算,全省每年从渠道渗漏掉的水量约为20亿m3。渠道输水渗漏量的研究一直是农田水利工程领域重要的研究课题之一。本论文基于系统的非饱和土壤有压入渗试验,探索了非饱和土壤有压入渗的入渗特性、主导驱动力和影响非饱和土壤有压入渗特性的主要因素;在考斯加科夫(Kostiakov)公式的基础上,建立了非饱和土壤有压入渗的三阶段经验模型;建立了以土壤物理参数和积水入渗水头预测土壤入渗能力和入渗参数的模型,提出了预测渠道土壤入渗过程的方法;在分析典型渠道渗漏过程的基础上,提出了以渠床点入渗参数估算渠道输水渗漏量的方法;借助数值模拟的方法,建立了均质渠道二维入渗的土壤水分运动数学模型。研究结果表明:⑴非饱和土壤水分有压入渗过程可用三阶段经验入渗模型表达。土水势梯度是土壤一维有压入渗的主导驱动力。压力势梯度则是有压入渗的主导驱动力之一。⑵土壤水分有压入渗条件下,除了土壤质地、干容重、含水量这些常规影响因素外,积水入渗水头也是影响土壤水分入渗的主要因素之一。在影响非饱和土渠床入渗能力的四个因素中,干容重的影响最为明显,土壤质地的影响次之,积水入渗水头最弱。⑶采用多元线性回归模型用常规物理参数对非饱和土壤入渗能力进行预报是可行的。以土壤物理性粘粒含量(小于0.02mm)、干容重、含水量和积水入渗水头作为预测量的变量可获得较好的预测结果。预测误差小于18%。⑷当土壤质地、结构、含水量一定的情况下,根据建立的非饱和土壤入渗参数模型,入渗参数可以表达为积水入渗水头的一元线性函数。利用沿断面湿周积分的方法可求得渠道断面的入渗量随时间的关系函数,从而求得渠道的渗漏量。并借鉴现有经验公式中自由渗漏量与顶托渗漏量、防渗渠道渗漏量的关系式,可获得顶托和防渗渠道的渗漏量。⑸借助土壤水动力学理论,建立了均质渠道二维入渗的定解问题,采用交替方向隐式差分格式(ADI格式)进行求解,应用土壤剖面含水率、土壤水湿润峰运移值和累积入渗量及入渗速率等指标的实测值与模型值对模型进行了验证。结果表明,两者具有较好的一致性,相对误差在15%以内。说明所建模型能比较真实地反映渠道土壤的水分运动情况。主要创新点:(1)基于考斯加科夫入渗模型建立了有压入渗三阶段经验模型,该模型更好地反映了有压入渗过程中入渗率变化特性,计算的累积入渗量误差在5%以内,与考斯加科夫三参数模型相比,可获得更高的模拟精度。(2)提出了点入渗参数与积水入渗水头间的函数关系,创建了利用点入渗参数,通过沿过水断面积分估算渠道输水损失量的方法。该计算模型通过入渗模型参数全面反映了渠道土质、干容重、含水量和水深对渗漏量的影响。与考斯加科夫公式计算结果相比较,计算结果可更真实地反映渠道渗漏量随时间的变化过程,并具有更高的精度。(3)借助土壤水动力学理论,构建了土渠床输水断面水分入渗的定解问题,实现了采用交替方向隐式差分格式(ADI格式)对定解问题进行求解。通过土壤剖面含水率、土壤水湿润峰运移值等指标的实测值与模型值计算值的比较,相对误差在15%以内。(4)建立了影响非饱和土壤水分有压入渗参数与各影响因素间的定量数学关系。分析得出:在影响非饱和土渠床入渗能力的四个因素中,干容重的影响最为明显,土壤质地的影响次之,积水入渗水头最弱。(5)采用多元线性回归模型用常规物理参数对非饱和土壤入渗能力进行预报是可行的。以土壤物理性粘粒含量(小于0.02mm)、干容重、含水量和积水入渗水头作为预测量的变量可获得较好的预测结果,初步实现了非饱和土壤水分有压入渗参数的预报。本研究以建立渠道渗漏量计算模型为目标,进行了土壤一维有压入渗量测定装置的研制,对非饱和土壤有压入渗条件下的入渗特性和主要影响因素进行了较为全面深入的研究,提出了以点入渗参数计算渠道输水损失的方法,但由于问题的复杂性和方法手段的有限性,许多方面的问题还未得到解决或者还停留在定性研究的水平上,还需要进一步进行更深入的研究。更多还原

【Abstract】 At the present time, traditional surface irrigation method is still the most popular one in our country, and open channel are used for more than 75% of all surface irrigated area. The channel seepage losses accounts for 33% of water consumption each year, and it is estimated that the water amount of the channel seepage losses is 2 billion m3 in Shanxi Province each year. Therefore, the research on channel seepage has always been a significant topic in water-conservation measure in agriculture.Based on the the pressured water infiltration experiments of unsaturated soil, the basic features, driving forces and influencing factors of pressure infiltration of Unsaturated earth channel were analyzed. Based on the Kostiakov infiltration formula,a empirical model with three subsection formulas used for simulating the course of the pressured water Infiltration into unsaturated soil was offered. A predicting model that predicts irrigation capability of water and parameters of predicting model by soil physical parameters of channel and water head was set up and a method of predicting irrigation process was put forward. Meanwhile a calculation model of channel seepage losses was set up by analyzing process of a classic trapezoid-transect channel. With numerical simulation, A soil water movement model of homogeneous channels of two-dimensional infiltration was established. Research results indicate:(1) The unsaturated soil pressure infiltration process accord with an empirical model with three subsection formulas. Soil-water potential gradient is the dominant drive force for pressure infiltration, while the pressure potential gradient is one of the major drive forces for pressure infiltration.(2) The infiltration capacity of Unsaturated earth channel is influenced not only by these basic physics characteristics such as soil texture, soil density and soil moisture, but also by the water head in channel. Among these main factors, the influence of soil density is the most obvious one, the influence of soil texture comes the second, and the influence of water head is the weakest.(3) Infiltration capability and infiltration model parameters can be predicted by multivariate linear regression model. Taking soil texture, soil density and soil moisture, and water head as predicting variables, the predicted results are satisfactory. The relative error between simulated and measured values is less than 18%.(4) When soil texture, soil density and soil moisture are given, the parameters of the infiltration empirical mode are functions of water head. The relationship between channel seepage losses and time can be obtained by utilizing integration, and then seepage losses of the irrigation channel can be calculated by the relationship among free leakage, backwater leakage and impermeable channel leakage in exiting empirical formulas. And the channel seepage losses of backwater and lined channel can be obtained too.(5) With soil water dynamics theory, a solution of two-dimensional infiltration of homogeneous channel was established,and was solved by using alternating direction implicit difference scheme (ADI format). By means of computer simulation, results of simulation were verified by the measurement of soil moisture content, water front, cumulative infiltration and infiltration rate in laboratory test. The results showed that the simulation results agreed well with measurement values. The relative error between simulated and measured values is less than 15% and so the predictability of the model is acceptable.Main innovation:1) A pressure infiltration empirical model with three subsection was established based on Kaosijiakefu infiltration model. The model can goodly reflects the infiltration rate of change in infiltration characteristics of the course of the pressured water Infiltration into unsaturated soil, the calculated cumulative infiltration error is less than 5%, compared with Kaosijiakefu three-parameter model, this model has higher simulation accuracy. 2) The functional relationship between point infiltration parameters and water infiltration head was offered. By utilizing integration , A channel estimation method using the point infiltration parameters of water loss was created. This calculation model fully reflects the effect on leakage affected by channel soil texture, dry bulk density, water content and water depth. The results can be more truly reflect the channel leakage process of change with time and has higher accuracy compared with the results calculated by the Kostiakov formula.3) Based on soil water dynamics theory, a solution of two-dimensional infiltration of homogeneous channel was definited,and definite solution of the problem was realized through alternating direction implicit difference scheme(ADIformat).Through the comparison between the field data of soil moisture content or soil moisture peak migration and model calculation data , relative error ban be within 15%.4) The quantitative mathematical relationships about the influence of pressured water infiltration parameters and the factors affecting in unsaturated soil was established.5) Pressured water infiltration parameters prediction of the unsaturated soil was preliminarily realized.Aimed at setting up the calculation model of channel seepage losses, the instrument which is used for measuring the one-dimensional pressured water infiltration has been worked out. The infiltration characteristics and major influence factors pressure infiltration of Unsaturated Soil were systematically explored in conditions of pressure infiltration. The method of calculating channel seepage loss through point parameters has been suggested. However, because of the complexity of the infiltration problem and limitation of means, various problems still haven’t been resolved or remain at the level of qualitative research . further intensive researches are needed.更多还原