用TDR快速确定非饱和土中水分的入渗锋面

Rapid Estimation of Water Infiltration Interface in Unsaturated Soil with TDR(Time Domain Reflectometry) Method

对低含水量土壤进行灌溉时在土壤中会形成水分的入渗锋面，垂直插入的ＴＤＲ信号可以在水分锋面形成二次反射。由ＴＤＲ（时域反射仪）测得的折合介电常数，平均含水量和锋面反射波三种方法来确定表土在非饱和灌溉条件下水分入渗锋面，与水分实际入渗距离进行对比分析表明用介电常数测得的锋面比用土壤水分计算结果准确，在初始入渗时，只有用锋面反射波方法计算的入渗深度才是可行的。

There is an water infiltration interface between dry and wetted parts when a soil profile of low moisture content is watered. If the soil moisture content around the interface is measured with TDR wave guide inserted vertically in the soil, a secondary reflecting TDR signal will be introduced, by which the depth of the interface can be estimated. The infiltration depth can also be determined with averaged moisture content method and reduced dielectric constant method. Comparing the results from these three methods with practical infiltration depth show that the results with secondary reflecting TDR signal is the best. In early stage of an infiltration procedure, only the results with secondary reflection wave method is reliable.