Experimental study of the air entrapment effects on soil structure and infiltration

The theoretical analysis and experiments are conducted to study the effects of the entrapped air on the soil structure and infiltration. We apply the 2.8 cm ponding depth at the soil surface to two the antecedent water contents and three porosities soil columns and measure the air pressure ahead of the wet front,the cumulative infiltration,and the change of soil structure. The theoretical and experimental results indicate that the air pressure can lift the saturated layer of soil near the surface to cause an upward disruption in the soil column in the wet front before the air pressure head reaches the air-breaking value.The disruption makes the bottom layer discontinuous with the top layer. The data from the infiltration experiments generally indicate that the structure changes of the infiltration soil are affected by the antecedent structure and water contents. For the consolidated and high water content materials,the change of the structure and air pressure is smaller,vice versa. In addition, the disruption lifts the soil in the surface and,in some cases,stops infiltration.