Modelling of thermally induced desiccation of geosynthetic clay liners in double composite liner systems

Abstract

Double composite liner systems (DCLSs) for municipal or hazardous waste landfills often include geomembranes (GMBs) and geosynthetic clay liners (GCLs). Heat generated within such landfills due to exothermic degradation of organic matter or hydration of incinerator ash creates thermal gradients across the liner. These thermal gradients have the potential to induce a movement of moisture and create a risk of desiccation of the mineral component of the GCLs. This paper presents the results of a simulation of moisture redistribution and discusses the potential for desiccation of GCLs in DCLSs when subjected to thermal gradients using a numerical model developed by Zhou and Rowe (2003). The results from a series of laboratory experiments previously reported by the authors (Azad et al., 2011) are compared with model predictions. Two alternative soil water characteristic curves (SWCC), proposed by van Genuchten (1980) and Fredlund and Xing (1994), are implemented and their effects on the model’s accuracy assessed. The original model is found to predict reasonably well water distribution and the likelihood of thermal desiccation of the GCL.