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HDPE liner panel orientation?

Q&A: GMA Techline | June 1, 2014 | By:

I am reviewing a construction report where a landfill cell has HDPE one-sided texture laid about 45 degrees from the direction of steepest slope across approximately one-third of the sideslopes.

I am looking for quantitative data on any testing done with this type of orientation or any opinions you may have on the potential for problems if we approve this construction (red flag?, yellow flag?, not-so-green flag?). I’m very hesitant to make them reconstruct and would need good reason to do so.

(Bob | Colorado)

Reply: We get this question fairly regularly but have never undertaken a research project on it. I think the reason is that: (a) we have not had field failures reported, and (b) if we focus on the seams (both peel and shear), there is actually a longer length (by 41% since it is on the bias) than the test with the seam perpendicular to the tension direction—i.e., 1.414 inches vs. 1.00 inch.

This leaves the question of what might happen in the field. If soil sliding occurs on top of the geomembrane, it could stress the sheet, hence the seams. But at typical seam strengths, it seems a stretch to me to result in adverse effects. That said, I would always shingle the adjacent sheets downgradient.

My last thought is to ask: “How does one go around a corner without some amount of seam being out of alignment with the downward slope?” I guess the answer might be to cut many pie-shaped segments but that is really onerous to the installer. How about a not-so-green flag?

Bob Koerner | GMA Techline

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