地下灌竖管灌水器湿润体时空变化规律

研究地下竖管灌水器的土壤湿润体特性时空变化规律及影响因素,对进一步研究竖管地下灌溉技术要素,并将这一节水灌溉技术用于实际具有重要意义。该文基于室内竖管灌水器入渗试验,研究了土壤物理特性参数(土壤初始含水率和土壤容重)、竖管灌水器工作压力水头和灌水器技术参数(竖管管径)对土壤湿润体空间分布的影响。根据试验数据,构建了在不同方向上竖管灌水器工作压力水头、土壤初始含水率、土壤容重、竖管灌水器直径和竖管灌水器埋深等因素与湿润体时空变化特征值的量化关系,其决定系数均在0.85以上。按标准化回归系数分析得湿润锋运移距离与压力水头、初始含水率、竖管直径及竖管埋深呈正相关,与土壤容重呈负相关。湿润锋在各个方向的运移距离由大到小依次为:向下、水平和向上。根据不同方向湿润锋运移距离和各影响因素的量化关系,建立了不同方向湿润锋运移速率和各影响因素的量化关系,这一关系表明:在入渗初期,各个方向的湿润锋运移速率较大,随着入渗时间的延续,其值逐渐减小,在200 min左右,开始逐步趋于稳定。

Temporal and spatial variation of wetting volume under sub-irrigation with vertical emitter

Abstract: The temporal and spatial variation of soil wetting characteristics and the influencing factors of vertical tube sub-irrigation were studied. In this article, the effects of working head, soil bulk density, initial soil moisture, diameter of vertical tube and buried depth of vertical tube on the spatial distribution of soil wetting were studied based on the experiment of indoor vertical tube emitter infiltration. In this experiment, the experiment was conducted using an orthogonal design method including 18 treatments. The orthogonal experimental design was adopted to arrange the influenced factors including water head, soil bulk density, initial soil moisture, diameter of vertical tube and buried depth of vertical tube (all the factors had 3 levels) and to study the characteristic parameters of wetted soil volume under sub-irrigation with vertical tube emitter. In the test, the pressure head was designed with different levels of 0.8, 1.1 and 1.4 m, and the soil bulk density was 1.32, 1.35 and 1.38 g/cm3. The initial soil moisture was 4%, 7% and 10%, and the diameter of the vertical tube was 4, 8 and 12 mm, the depth of vertical tube was 15, 20 and 25 cm. After the infiltration of started, observed and recorded the wetting front in the horizontal, upward and downward directions with the stopwatch, the corresponding wet body shape was obtained at different times. The cumulative infiltration into the soil was recorded by the scale on the Markov''s bottle. The result showed that the shape of the wet body formed by the infiltration test of the vertical tube emitter was approximately an ellipsoid, and the horizontal diffusion radius and vertical infiltration distance of the wetting body increased with the infiltration time. At the early stage of irrigation, the wet front was basically consistent in the 3 directions, the distance between the downward movement and the upward and horizontal directions gradually increased with time, and finally the downward migration distance was the largest. According to the wet front migration distance in the 3 directions recorded at different times, the water head, soil bulk density, initial soil moisture, diameter of vertical tube emitter and buried depth of vertical tube in the 3 directions were established by using multiple regression and the coefficient of determination was above 0.85, which showed the reliable quantitative relationship between the migration distance of the wetting body and the influencing factors. According to the standardized regression coefficients, the infiltration time, water head and soil bulk density had a significant effect on the wetting body. The influence of the water head, the initial soil moisture, the diameter of the vertical pipe and the depth of the vertical tube on the wetting body was positive correlation. The effect of soil bulk density on the wetting body was negative. The 5 factors had different influential degree on the characteristic parameters of the wetting body. When the vertical tube emitter diameter, the initial moisture content and water head were increased, the wetting distance was increased. According to the quantitative relationship between the wet front migration distance and the influencing factors in different directions, the relationship between the wetting front migration rate and the influencing factors in different directions was established. It showed that the wetting front migration rate began to increase at the beginning of irrigation. With the increase of infiltration time, the wetting front migration rate gradually decreased. After infiltration for 200 min, infiltration gradually stabilized.