Hydraulic conductivity of bentonite–polymer geosynthetic clay liners subject to wet–dry cycles used in landfill cover systems

Abstract

This study evaluated the hydraulic conductivity of bentonite–polymer (B-P) geosynthetic clay liners (GCLs) subjected to wet-dry cycles that simulated seasonal conditions on a GCL installed in a landfill cover system. Hydraulic conductivity tests were conducted on B-P GCLs and NaB GCLs at 10 kPa in accordance with the ASTM D5084 standard. Two wet–dry methods were used to investigate the hydraulic conductivity of the GCLs under different field exposure conditions. The hydraulic conductivities of the NaB and B-P GCLs gradually increased during four wet–dry cycles. However, the hydraulic conductivity of the B-P GCL (K = 2.3 × 10-12 m/s) was lower than that of the NaB GCL (K = 6.3 × 10-11 m/s) by two orders of magnitude after four permeation–drying cycles. In addition, the hydraulic conductivity of the B-P GCL was lower (K = 5.8 × 10-12 m/s) than that of the NaB GCL (K = 7.8 × 10-10 m/s) by two orders of magnitude after four saturation–drying cycles. The results suggest that B-P GCLs can enhance the effectiveness of landfill cover systems compared to Na-B GCLs in managing conditions during wet and dry seasons.