Thermal Analysis of GCLs at a Municipal Solid Waste Landfill

This study was conducted to determine long-term thermal regime of landfill liner systems using a field temperature monitoring program and numerical analysis of heat transfer. Temperatures in liner systems that contain geosynthetic clay liners (GCLs) were monitored prior and subsequent to waste placement. Data were collected in three cells at a landfill in Midwestern USA for more than five years. The liner system in one of the cells was left exposed (not covered with waste) for a period exceeding one year subsequent to cell construction. The lowest and highest GCL temperatures were –1°C and 35°C, respectively and the localized temperature gradients ranged from approximately –186°C/m to +134°C/m across the liner system during the exposed period. Seasonal temperature fluctuations were dampened and increasing temperature trends were observed after placement of the first lift of waste over the liner systems. Temperatures in liners reached 30°C under 5-year-old waste with an annual rate of temperature increase of approximately 4°C/a. In general, average temperature gradients decreased, however, high variations in gradients remained subsequent to waste placement. Numerical analysis was used for exposed liner systems to model observed behavior and to predict liner response under varied conditions. Good agreement was observed between measured and predicted temperatures. Temperature distributions in liners were determined for variable thicknesses of sand protective layers in 3 climatic regions. Sand thicknesses of more than 1 m were required to maintain temperatures between 0 and 40°C and thicknesses on the order of 3 m were required to limit seasonal temperature variations to within 10°C in GCLs.