Infiltration and surface geometry features of a swelling soil following successive simulated rainstorms

The theory of water movement in high shrink/swell soils has experienced consistent revision since Haines first presented the topic in 1923. Several aspects of the infiltration process in cracking soils have proven to be difficult to measure; seal/crust formation and properties, crack network patterns, preferential flow zones and contributions, and soil moisture determinations within the profile (near crack and near center of prismatic column) to name a few. Here, we used simulated rainstorms, laser measurements of surface elevation, needle-penetrometer measurements, and mass measurements of infiltrating water over a 206- and 145-d period to examine water movement and cracking patterns in a large sample box filled with a swelling clay soil. Water movement was restricted to the neighborhood of the crack zone, since the formation of a surface seal/crust prohibited infiltration into the surface of the prismatic columns of soil between cracks. Also, the location of cracks was observed to alternate between rainstorms. The alternating crack pattern led to more uniform wetting with depth as time increased and the number of rainstorms increased, thereby reducing the extent of preferential flow.