Experimental investigation of the influence of a geotextile beneath the geomembrane in a composite liner on the leakage through a hole in the geomembrane

Leakage through a composite liner having a damaged geomembrane and a geotextile filling the interface, between the geomembrane and the compacted clay liner (CCL), was investigated experimentally using a 1-m-scale device. The main emphasis of this study was to assess the influence of a geotextile on the flow rate. Three geotextiles were tested, two nonwoven needlepunched and one thermal-bonded geotextile, in a 1-m-scale device, for a constant CCL surface corresponding to a real topography from a landfill, under normal stresses of 64 and 134 kPa respectively. The methodologies for CCL molding in landfills and reproduction in the meter-scale device were specially elaborated for this purpose. Results revealed that: (i) the hydraulic behavior of some geotextiles depends not only on thickness but also on the prehydration and unsaturated properties of the geotextile, as shown by measurements of the geotextiles-water retention curves; and (ii) the hydraulic properties given by standardized tests are unreliable when it comes to predicting leakage rates in a composite liner with a geotextile at the interface. Consequently, geotextiles should be tested in conditions as close as possible to those of the landfill bottom liner in which they are to be used. (C) 2004 Elsevier Ltd. All rights reserved.