包气带气压计算及其影响入渗的模拟

Air Pressure in the Vadose-Zone Calculation and Its Impact on Infiltration Simulation

降雨入渗过程中土壤内空气压力的变化影响到土壤的入渗能力,当包气带气压大于地球表面大气压后会对入渗水流起到顶托的作用。本文根据包气带气压变化的观测结果理论分析了包气带气体运动的一般规律,并以此为依据假设气体外逸函数,然后推导土壤包气带中气压变化的计算公式,并通过模拟分析比较了考虑包气带气压前后入渗过程:均匀降雨条件下考虑包气带气压后开始积水时间提前,入渗率平均减小27%,有时减小程度可达32%;渗透总量在降雨初期差别很小,但到压缩外逸阶段后差别变大,时间越长,包气带气压的减渗作用愈显著,两者相差越大,24 h入渗总量平均减小约20%。

Air pressure change in the rainfall infiltration in the soil affect the soil infiltration capacity, infiltration of water when the air pressure in the vadose zone is greater than the Earth＇s surface atmospheric pressure plays the role of the backwater. Theoretical analysis of general laws of the air movement in the vadose zone was given according to the observations of air pressure change in the vadose zone , which was a basis for assuming the air escaping function and deriving the formula of the air pressure change. And then the impact on the infiltration was simulated considering the vadose zone pressure change. Under the uniform rainfall conditions, the start time of the water accumulating was shifted earlier and the average infiltration rate was reduced by 27%, sometimes up to 32%; the difference of total penetration was little in the early time of rainfall , but became great at the period of compression escape and the difference was greater when the reduction of infiltration became more significant and longer,, the total infiltration for 24 hours average reduced by about 20%.