边界透气性对降雨入渗的影响

The Impact of Different Gas Boundary Condition on Rainfall Infiltration

基于水气二相流理论,采用有限单元法计算了不同透气边界条件下的降雨入渗过程,探讨了边界透气性对稳定入渗强度、孔隙气压分布和饱和度分布等的影响。边界透气条件是渗流计算中的一个重要控制条件,传统计算多为定性研究,通过量化透气条件,分析边界透气性对降雨入渗的影响。结果表明:稳定入渗强度与边界透气性密切相关,边界透气性越小,稳定入渗强度受透气性影响越敏感,其敏感性随边界透气性增大逐渐降低,边界透气性对稳定入渗强度的影响呈对数关系。此外,边界透气性越小,降雨入渗过程中孔隙气压力越大,湿润锋推移速度越慢。

Based on the theory of two-phase （water and gas） flow, this study presents results from the finite-element analysis of soil rainfall infiltration on different gas permeable conditions, and analyzes the influence of gas boundary permeability on the stable infiltration intensity, pore gas pressure and soil saturation distribution. Gas permeable boundary is one of the essential control conditions in the seepage simulation. A quantitative analysis has been proposed to figure out the impacts of gas permeable boundary on the process of rainfall infiltration, while a majority of conventional studies focus on qualitative research. The simulation results indicate that there is a highly relevant relationship between stable infiltration intensity and gas permeability on the boundary. The stable infiltration intensity is sensitive when the gas boundary permeability is at a low stage, and as the gas boundary permeability going up the sensibility of stable infiltration intensity is declined. The equation between stable infiltration intensity and gas boundary permeability is regressed to be logarithmic. Besides, during the process of rainfall infiltration the pressure of pore gas soars up and the movement of wetting front slows down with lower gas boundary permeability.