Air Entrapment and Water Infiltration in Two‐Layered Soil Column

This study presents the experimental results of one‐dimensional unsaturated water infiltration under two conditions: vertical columns of homogeneous soil and vertical columns of two‐layered soil. The purpose was to more accurately identify the movement of the wetting front under both conditions. The results showed that air pressure buildup was more pronounced in soil columns of two layers than in soil columns of one homogenous layer. Water content in the top layer of a closed two‐layer column was greater than the corresponding height in a homogeneous one‐layer column. Flow conditions and pressure buildup in the bottom layer retarded the wetting front at the interface until pressure reached a maximum value in the bottom layer. An analytical model was developed that predicts the cumulative infiltration into the top layer as well as the travel time of the wetting front.