浑水膜孔灌入渗特性与致密层形成特性

水中带沙是浑水灌溉较清水灌溉的本质区别,为揭示浑水灌溉的节水减渗机制,通过浑水膜孔灌自由入渗室内试验,以清水入渗为对照,研究了浑水膜孔灌入渗能力、湿润锋运移距离、湿润体含水率、致密层土壤颗粒组成及落淤层厚度等随入渗时间的变化规律,提出了土壤含水率与湿润锋运移距离之间的量化模型,分别建立了落淤层厚度与入渗时间、滞留层的滞留量与滞留深度之间的关系。结果表明:浑水泥沙对土壤水分入渗的影响较大,在入渗结束时浑水较清水的累积入渗量减幅达27.83%;土壤含水率从膜孔中心到湿润锋面逐渐减小,其减小的速率逐渐增大,湿润体半径方向的土壤含水率分布服从椭圆曲线分布。落淤层土壤细颗粒相对含量较浑水泥沙少,其物理性黏粒含量显著低于浑水泥沙。从土壤表面到6 cm入渗土层深度为浑水膜孔灌入渗滞留层,滞留层土壤细颗粒含量较原土壤增多,随着入渗土层深度的增大,土壤颗粒组成与原土壤差异逐渐减少,泥沙细颗粒滞留量随着滞留层深度的增大而减小。

Infiltration Characteristics of Muddy Water Film-Hole Irrigation and Formation Characteristics of Dense Layers

Sediment carrying in water is the essential difference between muddy water irrigation and clean water irrigation. The muddy water and clean water film-hole irrigation free infiltration experiments were conducted to reveal the water-saving and infiltration reduction mechanism of muddy water irrigation. The changes in the infiltration capacity of muddy water film-hole irrigation, the movement distance of the wet front, the moisture content of the wet body, the soil particle composition of the dense layer, and the thickness of deposition layer with the infiltration time were studied. The quantitative model between the soil moisture content and the wet front movement distance was proposed, the relationship between the thickness of deposition layer and infiltration time, and the relationship between the retention amount and the depth of stranded layer had been established respectively. The results showed that sediment in muddy water had a greater influence on soil water infiltration. At the end of the infiltration, the cumulative infiltration of muddy water compared with clear water decreased by 27.83%. The soil moisture content decreased gradually from the center of film hole to the wetting front, the decreasing rate of soil moisture content increased gradually, and the distribution of soil moisture content in the radius of the wetting body was an elliptic curve. The relative content of fine particles in deposition layer was less than that of muddy water sediment, and its physical clay content was significantly lower than that of muddy cement sediment. The infiltration depth from the soil surface to 6 cm could be used as the stranded layer of the film-hole irrigation with muddy water. The content of fine particles in the stranded layer was more than that of the original soil. With the increase of infiltration soil layer depth, the difference between the soil particle composition of the stranded layer and the original soil gradually decreased, and the retention volume of fine sediment particles decreased with the increase of the depth of the stranded layer.