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

Abstract

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.

Quantification of Fluid Saturations in Transparent Porous Media

“…These materials are representative of angular, poorly graded sands with d 10 , d 30 , and d 60 values of 0.75, 1.16, and 1.75 mm, respectively, for the coarse gradation and 0.13, 0.27, and 0.45 mm, respectively, for the fine gradation (Peters et al, 2011). The combination of fused quartz media and an oil mixture was used by Siemens et al (2013, 2014) and Siemens and Oldroyd (2014) to investigate unsaturated moisture migration in one‐ and two‐dimensional systems as well as by Siemens et al (2015) in heat transport experiments.…”

“…The investigation of multiphase flow using transparent porous media (Iskander et al, 2015), where the indices of refraction of the solid grains and the wetting fluid are matched (Frette et al, 1992; Stöhr and Khalili, 2006; Ovdat and Berkowitz, 2006; Kong et al, 2009; Peters et al, 2011; Siemens et al, 2013, 2014; Siemens and Oldroyd, 2014; Kashuk et al, 2014; Black and Take, 2015), is an alternative optical technique. The use of transparent porous media allows relatively inexpensive measurements to be made at high spatial and temporal resolutions for greater sample depths than are possible using light reflection or transmission techniques.…”

Determination of the hydraulic conductivity function of grey Vertosol with soil column test

“…Model predictions and measured values were compatible up to 300 mm depth whereas a very clear difference can be observed at 800 mm level. The main explanation for the difference could be the effect of the entrapped air during the wetting process ( Siemens et al., 2014 ). The effect of entrapped air has always been a complication in soil model setups and to minimize that a free drainage boundary was maintained throughout the complete wetting of soil column.…”

Quantification of the Transparency of the Transparent Soil in Geotechnical Modeling

“…Improved image clarity of image texture is associated with a greater degree of variation in pixel intensity. For example, image intensity changes with the degree of saturation of transparent soil [30][31][32], with unsaturated transparent soil yielding degraded optical clarity. Accordingly, the variation in pixel intensity is estimated by the intensity gradient in this research.…”