Assessment of geomembrane strain from pond liner bubbles

Abstract

Bubbles (a.k.a. whales) that develop from gas entrapped beneath a geomembrane in pond liner applications lead to localized increases in geomembrane strain that warrant evaluation. Results from three-dimensional, geometrically-nonlinear, finite-element analysis are presented to show how geomembrane stiffness, fluid depth, volume of entrapped gas, and interface friction affect the deformed shape of, and maximum strain in the geomembrane. It is shown that the deformed geomembrane follows a bell-shaped curve and that geomembrane strain increases as the fluid depth increases until the bubble is submerged. The extent to which the maximum strain increases with decreasing geomembrane stiffness and increasing volume of entrapped gas are quantified. Design and operation charts are presented to provide a practical means of assessing strain in existing geomembrane bubbles or identify maximum fluid depths to limit geomembrane strain to a target value.