初始含水率对斥水黏壤土入渗特性的影响

Effect of initial soil moisture content on infiltration characteristics of water-repellent clay loam

为了探究初始含水率对斥水土壤入渗过程的影响规律,通过室内二维土箱的滴灌模拟试验,设置6个初始含水率水平(4.78%,7.28%,9.97%,13.64%,16.07%,19.02%),研究了初始含水率对湿润锋运移距离、宽深比、累积入渗量、入渗速率和土壤水分分布的影响,并评价了不同入渗模型的适用性.结果表明:随着初始含水率的提高,湿润锋运移相同深度所需时间呈逐渐减小趋势,两者较好满足幂函数关系,湿润锋宽深比逐渐减小;累积入渗量变化趋势为先减小后增大;入渗速率整体趋势为逐渐减小,其中斥水程度峰值含水率附近的处理出现入渗速率短暂提高的现象;Kostiakov模型能够较好反映斥水黏壤土的入渗规律,且斥水程度越大,模型拟合精度越低;随着斥水程度增加,土壤水分逐渐向湿润体垂向中间区域集中,并出现过度饱和现象.该研究可为斥水土壤的入渗理论奠定一定的基础.

To explore the effect of the initial moisture content on water-repellent soil infiltration process,the wetting front movement distance,horizontal-vertical ratio,cumulative infiltration volume,infiltration rate and soil water content change with different initial moisture contents were stu-died by a drip irrigation experiment in two-dimensional soil box with 6 initial moisture content levels(4.78%,7.28%,9.97%,13.64%,16.07%,19.02%),and the applicability of the infiltration models were evaluated.The Results show that with the increase of initial moisture content,the time that wetting front moving the same depth required is gradually decreased,and there is a better power function relationship between movement distance and time,and the horizontal-vertical ratio of wetting front decreases gradually.The cumulative infiltration volume decreases first,then increases,and the overall trend of infiltration rate is gradually decreasing,and the water-repellent soil samples′infiltration rate is increasing briefly.The infiltration law of water-repellent clay loam can be better reflected by Kostiakov model.The higher the soil water repellency,the lower the model′s fitting precision.Soil moisture is concentrated on the middle area in the vertical direction,where appears an excessive saturation phenomenon with the increase of water repellency.