Data base of field incidents used to establish HDPE geomembrane stress crack resistance specifications

Abstract

Geomembranes made from high-density polyethylene (HDPE) have a relatively high percent crystallinity, and are therefore of concern with regard to stress cracking. The stress crack resistance (SCR) of HDPE geomembranes must be properly evaluated and specified accordingly. A research project was initiated in 1990 to investigate the stress cracking behavior of HDPE geomembranes in the field. A total of 16 field sites were located, in which HDPE geomembranes showed some degree of stress cracking. The SCR of retrieved field samples was evaluated by both the bent strip and notched constant tensile load (NCTL) tests. The test data indicates that the bent strip test could not adequately predict the stress cracking field performance of HDPE geomembranes. In contrast, the NCTL test could distinguish the SCR of the retrieved field geomembranes. Based on the NCTL test data obtained from the field geomembranes, a 100 hour transition time is recommended to be the minimum value for an acceptable HDPE geomembrane specification. In addition, a single point notched constant tensile load (SP-NCTL) test was also established for quality control and quality assurance purposes. The recommendation for the SP-NCTL test is set at 200 hours failure time under an applied load of 30% room temperature yield stress.