Effect of air permeability at the bottom on rainfall infiltration

Abstract

In geotechnical engineering, the permeability of air through soil has been recognized as a factor influencing the dynamics of subsurface water pressure, thereby playing a role in determining the stress levels experienced by the soil. This study employed the finite element method to evaluate the rainfall infiltration process, taking into account various air permeability boundary conditions, including air ventilation, air sealing, and quantified air permeability. The research also explored the relationship between boundary air permeability and infiltration capability, pore pressure, and saturation distribution. Two comparative analyses under ventilation and air sealing conditions were conducted using GeoStudio software to verify the validity of the numerical calculations, and errors consistently remained below 30%. The artificial rainfall simulation tests and automatic data acquisition were conducted under two distinct conditions: ventilation and air sealing. The results showed that a decrease in boundary air permeability had a pronounced effect on infiltration. The relationship between boundary air permeability and infiltration capability exhibited a logarithmic pattern. Moreover, lower boundary permeability values were directly correlated with increased pore air pressure during the rainfall infiltration process, resulting in a decelerated advancement of the wetting front. When comparing the test data under ventilation and air-sealing conditions, it was observed that air sealing restricted air escape, hindering rainwater infiltration and significantly reducing the infiltration rate. This also led to a gradual transformation of the saturated zone within the slope.