Service life prediction of co-extruded geomembranes with an ethylene vinyl-alcohol (EVOH) layer

Composite barriers consisting of a geomembrane (GM) overlying a compacted clay liner or a geosynthetic clay liner are used in municipal solid waste (MSW) and low-level radioactive waste (LLW) disposal facilities to limit the release of leachates. Organic contaminants can diffuse through geomembranes to groundwater, posing a serious threat to the environment and human health. Recent studies have shown that co-extruded geomembranes with an ethylene vinyl-alcohol (EVOH) layer provide superior resistance to organic contaminants compared to traditional high-density polyethylene (HDPE) geomembranes. Nevertheless, the long-term durability of co-extruded EVOH geomembrane remains unexplored. The aim of this research is to predict the functional lifetime of co-extruded EVOH geomembranes used in landfills. To achieve this aim, accelerated laboratory aging tests will be conducted to evaluate degradation of co-extruded EVOH geomembrane. Since co-extruded EVOH geomembrane is a multilayer structure, the degradation mechanism may be different than monolayer HDPE geomembrane. Shear tests will be conducted using self-designed shear test apparatus to evaluate the degradation of interface strength between different layers. A peel test apparatus will be deigned to separate each layer of co-extruded EVOH geomembrane so that mechanical degradation of each layer can be determined. GMs in disposal facilities are subjected to tensile strains which may accelerate the degradation of GMs. The effect of tensile strain on degradation of GM will also be evaluated. GMs are welded together (generally hot-wedge welding and extrusion fillet welding). GM wrinkles are formed due to solar radiation combined with a high coefficient of thermal expansion and in-plane limitations on expansion. GM seams and wrinkles may be the weakest locations, thus long-term performance of GM seams and wrinkles will be evaluated.