Interpretation of Transmissivity Test Data for Geonets

Abstract

Transmissivity tests were performed on a geonet confined between a pair of geomembranes under five increments of compressive stress ranging from 25 to 400 kPa. Each successive increment of stress was applied for 24 hours. In total, four geonets and seven geomembranes were evaluated in the test program. Measurements of flow rate per unit width through the geonet taken at five hydraulic gradients between the values of 0.02 and 0.10 indicate that the flow regime is semi-turbulent. Interpretation of the data addresses a comparison of flow behaviour in the geonet with that of fine gravel. A relative permeability factor is used to quantify the flow capacity in the semi-turbulent regime. The relationship between the relative permeability factor and the hydraulic gradient offers a useful approach for the estimation of flow capacity at gradients for which test data are not available. In contrast to the behaviour of gravels, a stress dependency of the curves may be expected at magnitudes of confining stress that result in a compression of the geonet and/or intrusion of the geomembrane into the apertures of the geonet.