Measurement of Gas Permeability in Geosynthetic Clay Liners in Transient Flow Mode

International audienceGeosynthetic clay liners (GCLs) are often selected as a part of the barrier layer for cover systems in solid waste landfills to prevent infiltration of rainfall and migration of biogas into the atmosphere. To address the ability of GCLs to mitigate gas flow through cover layers, this paper presents an apparatus and testing method to measure the gas permeability of non-saturated and strained GCLs in the laboratory. The test is performed following a transient gas flow regime, and the test results are interpreted using a simple analytical solution. A series of gas permeability tests was performed on a needle-punched GCL with a degree of saturation between 32 % and 47 %. The specimens were tested under a 20 kPa load and 1.3 % strain in the radial direction, whereas the gas flow was induced by a gas differential pressure of less than 4 kPa. The results show that both the apparatus and the testing method can provide a reliable, fast, and simple method to measure the gas permeability of GCLs