Volume 30, Issue 6 (November 2007)
A Column Apparatus for Investigation of 1-D Unsaturated-Saturated Response of Sand-Geotextile Systems
This paper is focused on the details of an experimental device that was used to investigate the transient unsaturated-saturated hydraulic response of sand-geotextile layers under conditions of 1-D constant head surface infiltration. The column was instrumented with inexpensive tensiometer-transducer devices to measure pore water pressures and conductivity probes to measure wetting front migration. The results of two tests are presented to demonstrate the use of the apparatus. One test was carried out using a sand column and the second test was nominally identical but included a horizontal woven geotextile layer at about mid-depth. The test results demonstrate that the apparatus can detect differences in the unsaturated response of the two systems. For example, transient ponding of water was measured above the surface of the geotextile layer commencing from an initial unsaturated condition despite the relatively high saturated permeability of the woven material. In addition, there was a small but detectable delay in the hydraulic flow after the wetting front reached the geotextile layer.