农业工程学报2016，Vol.32Issue(14)：15-21,7.DOI:10.11975/j.issn.1002-6819.2016.14.003
耦合基质区与裂隙网络的土壤优先流模型及验证
Preferential flow model coupling soil matrix with fracture network and its validation
摘要
Abstract
Preferential flow refers to such a flow transport pattern that water and solute flow round soil matrix, which accelerates soil water movement. Soil cracks are a part of reasons that lead to preferential flow. This study aimed to analyze soil preferential flow pattern in order to establish a model of preferential model based on soil fracture network. A field color tracer experiment was carried out in Ningxia University from July to September in 2015 under precipitation intensity of 20 and 50 mm/h, and rainfall duration of 20-60 min. The results showed that when the rainfall intensity was 20 mm/h, the water infiltration depth increased with the increase of rainfall duration and the preferential flow began to develop, but it was still overall-matrix flow and the preferential flow was only locally developed. When precipitation intensity was 50mm/h and the duration of rainfall was 20min, water flows bypassed the soil matrix and preferential flow phenomena was observed obviously. The infiltration depth exceeded the fracture depth after duration of rainfall increased to 50min, soil fracture had not play a major role in the soil water movement, and the flow patterns were overall-matrix flow. The results showed that the flow patterns were mainly matrix flow under lower rainfall or irrigation intensity, and preferential flow under higher rainfall or irrigation intensity. A coupling model of soil matrix and fracture network for simulating preferential flow was established (CP model). In this model, the soil medium was divided into matrix and fracture networks formed by flow channels, each having its own saturated hydraulic conductivity and water movement equation. These equations were solved by using the control volume finite element method, and the nonlinear equations were linearized by Newton-Raphson methods to improve the convergence, and shorten the operation time. Equation of water movement in matrix and fracture network flow equation were coupled using global approach which solved the problems of the flow mutual influence caused by the cross-fracture network, and improved the computational efficiency. The validity of the proposed model was tested by the analysis of the soil moisture content between the simulated and the observed values. The results showed that the root mean squared error (RMSE) of soil moisture was 0.016-0.025, R2 of soil moisture was above 0.78, bias was 0.020-0.026, index of agreement (IA) was 0.918-0.938, indicating good simulation by the CP model. In the end, different crack structure but statistically equivalent networks was generated to validate the model simulation and produced well simulation results. These numerous fractures had stable effect on the variances of soil moisture. The results of this paper can provide valuable information for analyzing preferential flow and the coupling mechanism of the water content and solute transport between soil dry shrinkage crack and soil matrix.关键词
裂隙/土壤/模型/优先流/数值模拟Key words
cracks/soils/models/preferential flow/numerical simulation分类
农业科技引用本文复制引用
朱磊,陈玖泓,刘德东..耦合基质区与裂隙网络的土壤优先流模型及验证[J].农业工程学报,2016,32(14):15-21,7.基金项目
国家自然科学基金 （）
