Using multiaxial testing to determine the effects of temperature on high density polyethylene geomembrane liners

Geomembranes (GMs) are increasingly being used to line containment faciliti es for both hazardous and municipal wastes. The most common GM in the USA i s high density polyethylene (HDPE), a tough polymer showing good chemical r esistance, thereby helping to protect the environment from leachate emissio ns from landfills. The work presented here uses a form of multiaxial testin g, called the comprehensive test system (CTS), for geomembranes to perform testing in a manner reflective of the field application. The key mechanical testing distinction of the CTS is that of applying load to the sample with granular media. Liners are exposed to a wide range of temperatures from pr e- to postconstruction, and under a wide range of seasonal and latitudinal conditions. This work evaluated the effect of temperature on GMs using the CTS approach. The test time required to elicit changes in the material prop erties as a function of elevated temperature was considerably reduced by co mparison with the US Environmental Protection Agency standard tests. The da ta showed that the delta modulus (a measure of the material strength) decre ased with increasing temperature, indicating a loss of material strength. M ost importantly, an increase in temperature weakened the GM in a linear fas hion throughout the range studied, with no indication of a threshold temper ature.