Laboratory Investigation of Geosynthetic Clay Liner Desiccation in a Composite Liner Subjected to Thermal Gradients

Geosynthetic materials such as geomembranes and geosynthetic clay liners (GCLs) are frequently used in composite liners for municipal solid waste landfills. Heat generated within such facilities due to decomposition of organic material within the waste creates thermal gradients that have the potential to cause desiccation of the mineral component of GCLs, with potential impacts on long-term performance. This paper presents the results of an experimental investigation into the potential for moisture redistribution in and around GCLs forming part of a composite liner system when subjected to thermal gradients. Large-scale laboratory testing was performed using two different subsoils and GCL materials, with emphasis placed on the spatial and temporal variation of temperature and water content within and beneath the GCLs. The influence of key initial and boundary conditions such as the applied temperature gradient, initial GCL and subsoil water content, and the type of GCL is discussed, as well as the implications of the findings for long-term GCL performance. Recommendations are made regarding aspects of the design and operation of landfill facilities likely to reduce the potential for desiccation.