From the GMA Techline
Subject: Geomembrane wrinkles during installation— What is the general state of practice for limiting wrinkles during geomembrane installation? What is the maximum wrinkle height that should be allowed? Should it be trapped straight up or allowed to fold over? Thanks. (Ernest, New York)
Reply: Years ago, I thought that small wrinkles would flatten out when overburden was applied. Unfortunately, they do not. Even wrinkles as small as 14mm do not disappear under very large normal stresses. I’ll post a paper on the subject to you in this regard.
The bottom line is that the geomembrane must be flat against the subgrade when it is backfilled.