基于分层假设的Green-Ampt模型改进

传统Green-Ampt入渗模型由于假设过于简化而限制了计算精度,针对这一问题,在分层假设的基础上对模型进行了改进:将均质入渗土壤分为饱和层、过渡层和干土层,采用Richards模型分析了不同入渗条件下各层的厚度以及各层内含水率和导水率的变化规律,结果表明,入渗条件一定时,过渡层占湿润层(包括饱和层和过渡层)比例会随湿润层厚度的增加线性减小,积水深度和土壤初始含水率分别会影响这一线性关系的纵轴截距和斜率,而土壤饱和导水率则对其没有明显影响;过渡层内土壤含水率分布为椭圆形曲线,而导水率随深度增加线性减小。在此基础上,通过引入湿润层的等效导水率并相应给出锋面吸力的计算方法,对传统Green-Ampt模型进行了改进。结果显示,改进后模型计算精度显著提高。

Modification of Green-Ampt model based on the stratification hypothesis

A modification of Green-Ampt model is proposed based on the stratification hypothesis,which dynamically divided the soil column is into saturated layer,transient layer and dry layer.The model uses the concept of an equivalent hydraulic conductivity in the saturated layer,and employs a new method to estimate the Green Ampt wetting front suction.The Richards equation is used to simulate the soil water movement through all three layers,and to study the properties of soil layers including the thickness,the soil water content,and the hydraulic conductivity.The results show that the ratio of the transient layer to the saturated layer decreases linearly as the soil profile becomes wetter.Moreover,the ponding depth and the profile of initial soil water content influence the interception and the slope of the linear relationship.However,the saturated hydraulic conductivity is found to have no measureable influence on the relationship.The soil water content in the transition layer follows an elliptical distribution,and the hydraulic conductivity decreases linearly with the increase of the soil depth in the layer.The infiltration process can be better simulated by the modified Green-Ampt model.