Geomembrane patching? Landfill cooling?
Questions and answers from the GMA Techline
I am sizing a cushion geotextile that will be protecting a 40-mil LLDPE closure geomembrane against 2in.–4in. crushed, angular gravel. I understand that the equation for factor-of-safety (FS) against puncture, as presented in Section 5.6.7 of Designing with Geosynthetics, and the Reduction Factor for Creep, as presented in GRI White Paper #14 were obtained for 60-mil HDPE. Would there be much difference in the RF-creep and the P-allow for a 40-mil LLDPE geomembrane? If so, how could I account for this?
Thank you for your time and service to the geosynthetics industry.
(Tyler | South Carolina)
You ask a difficult question because the development of the method is based on
60-mil HDPE. It is actually the 50 kPa value in the equation. For 40-mil LLDPE, I would suspect that it is larger since its elongation is much greater. For example, elongation at break in large-scale axisymmetric (out of
plane testing per D5716) testing is 25% for HDPE vs. 75% for LLDPE.
If you use the formulation as shown in the references you will be conservative in the subsequent geotextile mass. If you increase the value to compensate for the increased elongation, I really don’t have a good value to suggest. Sorry about that.