Study of water flow under gravity and pressure through granular solids

These experiments concern the movement of water through soil. The principal variable of interest is the volume of water that has passed vertically through a column of soil observed at regular time intervals. The core of the experimental apparatus is a vertical tube (the test section) that is roughly 2 m long with a 3.18 cm inner diameter. The lower portion of the test section is filled with a sample of soil (200 mL) followed by a volume of water (1200 mL). In each experiment, this water is allowed to pass downward through the soil sample and out through a 0.95 cm diameter hole. From there, expelled water passes through a short flexible tube into a collection beaker. The volume in the collection beaker is monitored by an automated system with a sampling frequency of 10 Hz. More accurately, the level of water in the beaker is monitored with a laser ranging device, the beam of which is reflected off of buoyant opaque particles -- flakes of dried parsley -- that remain on the surface as the beaker fills. The apparatus is also fitted with a system for pressurizing the test section to a constant pressure up to a maximum of around 1200 hPa (1.2 atm).