Thermally Induced Desiccation of Geosynthetic Clay Liners in Landfill Basal Liner Applications

High temperatures may be encountered at the base of a landfill due to exothermic decomposition occurring in the overlying waste mass or hydration of ash. The corresponding thermal gradients create a risk of outward moisture movement and desiccation of the mineral component of composite lining system. This paper examines the potential effects of this thermally driven moisture movement on the long-term performance of geosynthetic clay liners in landfill basal liner applications. The results of large-scale laboratory experiments conducted in an effort to assess the behaviour of GCLs subjected to thermal gradients in landfill basal liner applications are discussed. In conjunction with this experimental program, a series of numerical models have been used to evaluate the pertinent thermal, hydraulic and mechanical properties of the soil and geosynthetic components of a composite liner system. The combination of insights gained through these programs allows a better understanding of the underlying mechanisms of moisture redistribution and desiccation behaviour. An analysis of the key results obtained through this investigation is presented. The discussion focuses on potential areas of concern with regards to thermally induced desiccation of geosynthetic clay liners. It is recommended that the potential for desiccation be addressed at the design stage of landfill construction, with numerical modeling used to identify potential risks. The avoidance of GCL placement over dry subsoils and the importance of managing heat generation within the landfill are stressed.