| 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.
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