Questions and answers from the GMA Techline
We’ve been doing work for some of our clients to try to use sub-angular crushed granite in leachate collection systems instead of rounded river-run gravel. The transportation costs for both materials are high here in Florida because they’re imported from Alabama or Georgia, but the costs for the rounded gravel are significantly higher. It seems that using sub-angular material in leachate collections is more common elsewhere in the country, but the convention here in Florida has been rounded river-run.
We have evaluated the geomembrane cushioning for sub-angular gravel based
on design methods published by GSE (Narejo) and based on your GRI White
Paper #14. Our calculations show that
we can provide adequate protection with
a 32-oz/sy geotextile according to these methods. My question is how do double-sided geocomposites compare to the
I saw your comments in the Geosynthetic Institute website FAQ section that indicates research has recently been concluded and is soon to be published. Do you have any additional information that you can share?
(Tom | Florida)
You ask a question we get frequently and about a year ago we finally got around to doing the requisite testing. Furthermore, we wrote a paper on it and we will send a copy to you.
Specifically, if the puncturing object is located beneath the aperture of the geonet, the puncture protection is afforded only by the sum of the two geotextiles. However, if the puncturing object is in the vicinity of a node then you get improved puncture resistance, but how much is unknown.
As a conservative suggestion, take the worst-case scenario.
Lastly, RE: cost, I suspect that a geonet composite is about the same as a 20-oz/sy geotextile so your 32-oz/sy is not too much more expensive.