Physical and numerical modeling of infiltration including consideration of the pore-air phase

Infiltration is a vadose zone process of interest to a wide range of research communities including agriculture, soil physics, and geotechnical engineering. In geotechnical engineering, transient infiltration is important to moisture balance problems such as cover systems, capillary breaks, and landslide triggering. Design of cover systems, capillary breaks, and landslide analysis applications depend on accurate models for the transient pore pressure and moisture migration response under a wide range of environmental conditions. Infiltration is typically modeled using Richards' equation, which assumes no impedance from the pore-air phase. However, if this assumption is invalid, the ground response during infiltration is significantly affected. An optically matched pore fluid - transparent soil, which allows for high temporal and resolution measurements of degree of saturation, was used to examine the effect of air entrapment on infiltration. Homogeneous and layered profiles were subjected to closed and open infiltration conditions. Following the completion of the experimental program, the results were simulated using a finite element program that allows for consideration of the air phase during infiltration. The results show the impact of ignoring the effect of air entrapment is to significantly underpredict the time to saturation and overpredict the pore pressure response.