Stress-Cracking Resistance of High-Density Polyethylene Geomembranes

A new index test method, the notched constant tensile load (NCTL) test, for evaluating high-density polyethylene (HDPE) geomembranes regarding stress-cracking resistance is presented in this paper. Eighteen commercially virgin geomembranes and 7 field-exhumed geomembranes were evaluated using the new test. Results show a wide variation in the onset of the transition time. For the 18 virgin geomembranes, the transition times range from 10 hours to 5,000 hours. In addition, all 7 field-exhumed geomembranes, where failure actually occurred, show transition times less than 100 hours. An evaluation of the test results leads to a tentative recommendation that the transition time for an acceptable HDPE geomembrane should be 100 hours or longer. A comparison between the results of NCTL test and the currently used ASTM D 1693 bent-strip test was conducted. It indicates that the bent-strip test cannot adequately evaluate stress cracking resistance, and that the NCTL test is a more critical test in the assessment of such behavior.