土壤介质特征对水分再分布过程中指流发育的影响

Effects of medium characteristics on finger flow during soil water redistribution

指流研究对农业水肥资源有效利用、环境和水资源污染防治等具有重要意义。为研究土壤介质特性对水分再分布过程中指流发育的影响,该文采用粗质石英砂和细质石英砂2种不同的土壤介质进行试验,探讨了土壤质地、土壤结构(包括均质土体、质地成层土体和湿度成层土体)、土壤初始含水率等土壤介质特征对水分再分布过程中指流发育的影响。通过分析试验结果可知,水分再分布过程中,土壤质地较粗时易于形成指流;增大土体初始含水率会抑制指流的形成和发展;湿润锋向下推移速度受土体初始含水率和指流发育情况的耦合影响;与均质土体相比,细质石英砂覆盖于粗质石英砂之上的层状结构土体中指流的形体更为明显,但其指流发育所需的时间相对较长;而由湿度不同构成的层状结构土体中指流发育进程较慢、程度较弱。研究表明,水分再分布过程中,土体介质的质地、结构和初始含水率等特性能够对指流现象的发生、发展产生重要影响。

Research on finger flow has practical guiding significance to effective utilization of agricultural water and fertilizer resources and to protection of environment and water against pollution.In order to understand the effects of medium characteristics on finger flow during the redistribution following the infiltration process of soil water,in this paper,an experimental study was carried out to discuss the effects of the characteristics of soil medium on the development of finger flow during redistribution with two different grain sized sands.The medium characteristics considered in this work were soil texture,soil structure and soil initial water content.Three soil structures,i.e.homogeneous soil,texture-layered soil and humidity-layered soil,were designed in this study.The experimental results showed that finger flow could easily occur in dryer and coarser homogeneous soil during water redistribution since both wetter and finer soil medium were proved to have disadvantageous effect on development of finger flow.The moving speed of wetting front was determined by both development status of finger flow and soil initial moisture content.Moreover,finger flow was greatly advanced in texture-layered soil with coarser soil overlaid by a finer soil layer compared with that in homogeneous dry coarser soil during water redistribution though it needed more time to develop,while the development of finger flow was restrained in humidity-layered soil with a wetter soil layer overlaid by a dryer soil layer.It was suggested that soil characteristics such as texture,structure and initial water content would have important effects on formation and propagation of finger flow during water redistribution.