Several Main Characteristics Of The Movement Of Preferential Flow In The Heterogeneous Soil Type Research

Natural soil profiles are mostly heterogeneous rather than homogeneous,and this heterogeneous structure greatly affects the spatial differentiation characteristics of soil water movement.It is of great significance for water resources and water environment protection to clarify the infiltration process of infiltration water in different heterogeneous soils.Based On the indoor infiltration experiments of soil column irrigation,the infiltration law and preferential flow characteristics of water in different heterogeneous structural types of soil,such as horizontal layered soil,horizontal interlayer and inclined interlayer soil,massive heterogeneous area soil,were studied by using dye tracer technology,image processing technology,sampling analysis technology and statistical methods.The purpose is to provide a reference for the efficient utilization of water resources and the prevention and control of groundwater pollution.The main results of the study were as follows:(1)Both fine soil layer covering coarse soil layer and coarse soil layer covering fine soil layer can retard irrigation water infiltration,but the formation mechanism of the two kinds of layer structure was different,the former was capillary barrier effect,and the latter was hydraulic barrier effect.The comparative test results showed that the water blocking effect of hydraulic barrier was more obvious than that of capillary barrier.The horizontal interlayer in the soil with horizontal interlayer(fine soil with coarse soil and coarse soil with fine soil)can also effectively retard the infiltration of irrigation water and increased the water content of the soil above the interlayer,so the soil with interlayer can effectively reduce the deep leakage of irrigation water and improved the utilization coefficient of irrigation water.The development of preferential flow in the fine texture frame was more obvious than that in the coarse texture frame,and the overburden under the double-layer structure reduced the development degree of preferential flow.In the three-layer structure,the horizontal interlayer of coarse texture reduced the heterogeneity of water flow movement in the fine texture frame,while the horizontal interlayer of fine texture increases the heterogeneity of water flow movement in the coarse texture frame.(2)Due to the diversion effect of the inclined interlayer,whether it was a coarse-grain sandwiched with a fine-grained inclined sandwich structure or a fine-grained sandwiched with a coarse-grained inclined sandwich structure,it would obviously hinder the infiltration of water flow,and this hindering effect was stronger than that of the horizontal sandwich structure;The comparative study results showed that the blocking effect of the inclined interlayer structure with fine texture and coarse texture on the infiltration flow was stronger than that of the inclined interlayer structure with coarse texture and fine texture.Different from the penetrating inclined interlayer,the existence of the locally inclined interlayer had no obvious effect on the water content of the overlying layer after irrigation,indicating that the locally inclined interlayer structure had a weak blocking effect on the infiltration water.Combined with the characteristic index of preferential flow,it was found that the inclined coarse interlayer increased the heterogeneity of flow movement,while the inclined fine interlayer decreased the heterogeneity of flow movement.The locally inclined coarse interlayer can reduce the heterogeneity of water flow to a certain extent,while the locally inclined fine interlayer increased the heterogeneity.(3)Both coarse and fine patchy heterogeneous areas can increase the water retention capacity of the upper soil layer,but they had different effects on the heterogeneity of infiltration flow movement;the coarse patchy heterogeneous area reduces the heterogeneity of infiltration flow movement in its soil layer,while the fine patchy heterogeneous area increases the heterogeneity of seepage flow movement in its soil layer.Compared with the horizontal interlayer structure,the blocking effect of the massive heterogeneous area on the infiltration flow was relatively weak,but the heterogeneity of the infiltration flow movement was higher.