Experimental evaluation of HDPE geomembrane seam strain concentrations

Laboratory testing was conducted to evaluate strain concentrations adjacent to high-density polyethylene (HDPE) geomembrane seams loaded in tension perpendicular to the seam. Strain concentrations were evaluated using digital image correlation (DIC) on specimens meeting the ASTM criteria for wide-width tensile testing. The tensile strain in the zone of strain concentration adjacent to the seam from the DIC analysis was compared to the strain predicted using theoretical seam strain concentration factors. While the average strain in the zone of strain concentration was relatively close to the theoretical value, the maximum tensile strain in this zone was significantly greater than the value predicted using the theoretical strain concentration factors. For average (global) tensile strains in the order of 3%, maximum strains measured by DIC in the zone of strain concentration were in the order of 9 to 11%, compared to values on the order of 5 to 6% predicted using the theoretical strain concentration factors. These findings suggest that the allowable tensile strain for HDPE geomembranes that will be loaded in tension perpendicular to the seam should likely be less than 4%, and that construction quality assurance specimens for destructive testing should not be recovered from areas where the geomembrane may be loaded in tension.