Gas permeability of geosynthetic clay liners overlap seams

This paper examines the gas flow performance of needle-punched geosynthetic clay liners (GCLs) overlap seams over a range of gravimetric moisture content, including the effect of vertical stress and unevenness of the overlaps. The gas permeability of the GCL overlapped seams was higher than that of non-overlapped GCLs, especially at higher gravimetric moisture content, as the intactness of the overlapped areas was challenging to maintain due to the GCL swelling process. The gas flow rate of uneven overlapped GCLs was greater than that of a flat overlap (even seam) irrespective of the vertical stress. This paper highlights the importance of factoring in the gas flow assessment of cover systems the possibility of the unevenness of the GCL panels overlaps.