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 pre-hydration 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.