Potential for Desiccation of Geosynthetic Clay Liners Used in Barrier Systems

Abstract

The potential for the desiccation of a geosynthetic clay liner (GCL) forming part of a single composite landfill liner is evaluated. A thermohydromechanical model is used to identify conditions likely to cause desiccation. Simulations for typical landfill conditions show that the potential risk of desiccation exists even at relatively low temperatures (i.e., 35°C). It is found that the water content of the GCL prior to waste placement, the liner temperature, the overburden stress, the grain size and water content of the subsoil, and the depth to aquifer all affect the potential for desiccation. The results suggest that the placement of GCLs directly over coarse-grained soils or drainage layers should be evaluated carefully. This study highlights the need for more research into the potential for GCL desiccation and, in particular, the need to establish water retention curves for different GCLs over a range of stresses and degrees of hydration before heating, so that the effect of stress and hysteresis on the potential for desiccation can be examined. The findings of this study are limited by the approximations and assumptions described in the paper and, even then, apply only to the GCL and conditions examined. Changing the assumptions may change the findings. The findings should not be generalized to other composite liners without independent verification. The results serve to identify some of the situations that may lead to GCL desiccation, and it is hoped that they will prompt more research on this important topic.