Durability of HDPE Geomembrane Seams Immersed in Brine for Three Years

This paper examines the long-term durability of two dual wedge welded 1.5-mm-thick high-density polyethylene (HDPE) geomembranes (GMBs). The two GMBs, which had different resins, and the welds initially met relevant standards. The welded GMBs were immersed in a brine solution with 200g/L total dissolved solids and pH 8.7 at four different temperatures (40, 65, 75, and 85 degrees C) for 3 years. Changes in standard oxidative induction time (Std-OIT) and high-pressure oxidative induction time (HP-OIT) were monitored at (1)the GMB well away from the weld, (2)the heat-affected zone beside the weld, and (3)the welded zone. The Std-OIT and HP-OIT depletion were fastest in the heat-affected zone adjacent to the weld and slowest in the weld itself. Both the Std-OIT and HP-OIT were still depleting, without having reached a residual value, when degradation in physical properties was observed. Brine has a greater effect on time to nominal failure for the peel break strength than for the shear break strength and elongation. Aging of the GMB in the heat-affected zone beside the weld controls the time to nominal failure. The importance of the welds in the consideration of GMB service-life is highlighted. (C) 2017 American Society of Civil Engineers.