On GCLs' Gas Permeability for Modelling of Gas Leakage Rate through GM/GCL Composite Liner Due to a Defect in the Geomembrane

The aim of this paper is to assess the validity of the geosynthetic clay liner (GCL) gas permeability coefficient obtained by the conventional testing approach for predicting gas leakage rate of GM/GCL composite liner due to a defect in the geomembrane. As a GCL is a composite-layered material, its permeability is a function of the permeability of its components (i.e bentonite and geotextiles) and flow direction. In order to investigate GCL's flow pattern under leakage condition, numerical experiments were conducted where for sake of simplicity the interface zone between the GM and the GCL has been ignored. The results show the inadequacy of using the GCL's gas permeability coefficient, obtained by the conventional testing approach, alone to predict the leakage rate. Instead, this value should be used along with the permeability coefficient of the GCL's geotextile layer to accurately describe the flow through GCL under leakage condition.