【摘要】 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。更多还原

【Abstract】 A simulation study of the infiltration rate was conducted for four soils with different rain patterns. Computational results showed that the rain water was infiltrated into soil when the infiltration rater was greater than the rain rate at the earlier stage of the rain, and then the infiltration flow was calculated by analogy with saturated piston-flow, the infiltration rate was in direct proportion to the suction head at the wetting front, a front of demarcation between saturated and unsaturated zones, and in inverse proportion to the saturated zone length. With the definition of nondimensional suction head equal to the suction head divided by its maximum one, the nondimensional heads calculated from the theory of Mein and Larson and predicted by the simelation study were in good agreement.By using the piston-flow concept, the method to determine the ponding time and wetting front depth has been derived in this study. Also, the analytical solution for infiltration rate and wetting front location below the soil surface, during the period when rain intensity is alwayes greater than infiltration, has been obtained.更多还原