DURABILITY OF HDPE GEOMEMBRANE SEAMS AND SHEET IN BRINE AND LANDFILL LEACHATE
The geomembrane (GMB) properties and those of the welds connecting the GMB sheets are key factors affecting long-term liner performance. Thus, a series of accelerated immersion tests are used to examine the effect of landfill leachate and brine on HDPE geomembrane (GMB) sheet and seams. The effect of ageing in these solutions was investigated at: (a) the GMB sheet well away from the weld (SAW); (b) the heat affected zone beside the weld (HAZ); and, (c) the welded zone (Weld). The initial, post-welding, Std-OITo and HP-OITo were greatest for the GMB away from the weld, and least for the GMB in the weld. A comparison of the degradation of sheet material in tension with the weld in shear, peel, or tension showed faster degradation of the weld than the sheet material immersed in brine and leachate. No physical degradation of the welds occurred until after the Std-OIT was depleted when immersed in MSW leachate, whereas in brine the shear and peel strength and elongation started to decrease before Std-OIT and HP-OIT had depleted to a residual value. No failure was observed in the welded seams themselves. Rather, failure was observed at HAZ adjacent to the weld in peel, shear, and tensile tests. The time to nominal failure (i.e., 50% of the initial value) for a seam was about 67% and 45% in brine and leachate, respectively, of that for the sheet aged under the same conditions based on both tensile strength and elongation; thus, the welds are likely to dominate the service-life of the GMB. Brine is shown to have a greater effect on the physical properties than landfill leachate based on all common indicators (i.e., shear break strength, shear break elongation, and peel break strength), resulting in shorter time to nominal failure, tNF, in brine (despite a high percentage of antioxidants remaining in the GMB at tNF).