The Effect of Bulk Density and Initial Water Content on Infiltration in Clay Soil Samples

Infiltration measurements were made on swelling clay soil samples packed into columns. Small increases in bulk density over the range 1.10 to 1.25 g/cm 3 markedly decreased the rate of water movement. The magnitude of the effect was greater for confined samples than unconfined samples at all initial water contents. A 1‐cm compact layer in the profile retarded water movement if the soil was confined. In partially confined samples the soil in the compact layer would swell on wetting, and water movement was retarded only when the bulk density after swelling still exceeded the bulk density of the remainder of the column. Bulk densities below 1.05 g/cm 3 , and heat of wetting in partially confined samples with 0% initial water content produced nonlinear distance to wet front vs. square root of time relationships. Comparison of horizontal and vertical infiltration showed that under these experimental conditions gravity contributed significantly to water movement at high initial water content.