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本文从描述非饱和土壤中水分流动的基本方程出发,对4种不同典型土壤在各种假定的均匀降雨速率下的入渗速率进行了数值模拟。结果表明,在降雨初期,由于降雨率低于入渗率,故全部雨量入渗,但当雨率大于入渗速率之后,入渗流动可以比拟为饱和水柱向非饱和区推进的柱塞流,其速率与饱和水柱长度成反比,而与分隔非饱和区与饱和水柱的湿润阵面上吸力大小成正比。如果对实际计算的吸力与Mein及Larson所推荐的理论计算吸力分别按各自最大吸力进行无量纲化,发现二者值吻合得很好。根据柱塞流这样一个概念,本文推导了决定入渗率等于雨率时的时间及该时的湿润锋面位置,并继而推导了在此以后,如果雨率永远大于入渗率情况下(并且不考虑地表有积水)入渗速率与湿润锋面位置的解析解,大大地简化了入渗率的工作量,具有实际应用的意义。
In this paper, based on the description of the basic equations of water flow in unsaturated soils, the infiltration rates of four different typical soils under various assumed uniform rainfall rates are numerically simulated. The results show that during the initial rainfall, all the rainfall infiltrates because the rainfall rate is lower than the infiltration rate. However, when the rainfall rate is higher than the infiltration rate, the infiltration flow can be compared with that of the saturated plunge flow into the unsaturated zone. The rate is inversely proportional to the length of the saturated water column and directly proportional to the suction on the wetted surface separating the unsaturated zone from the saturated water column. If the actual calculated suction and Mein and Larson’s recommended theoretical calculation of suction respectively, according to their respective maximum suction dimensionless, found that the two values are in good agreement. According to the concept of plug flow, we deduce the time when the infiltration rate is equal to the rain rate and the wet front position at that time, and then deduce that from then on, if the rain rate is always greater than the infiltration rate (and not Taking into account the surface water) infiltration rate and the location of the wet front analytic solution, greatly simplifying the workload of the infiltration rate, with practical significance.