Measurement of air permeability of geosynthetic clay liners

Hydraulic barrier layer is the major component in the cover system of a modern land"ll. The primary function of the barrier is to limit the amount of water in"ltration. Another important function is to minimize the emission of land"ll gas. In recent years, geosynthetic clay liners (GCLs) have been used in land"ll covers as hydraulic barrier layer. However, in hot and arid areas the bentonite in GCLs may develop desiccation cracks. Before the cracks are closed upon wetting, signi"cant amount of land"ll gas might have already emitted into the atmosphere. To address this issue, air permeability tests were performed to assess the e!ectiveness of GCLs as a gas barrier. The results show that air can hardly pass through hydrated GCL specimens. However, the drying of GCLs induced signi"cant increase of their air permeability. ( 200