Hydraulic conductivity to Jet-A1 of GCLs after up to 100 freeze-thaw cycles

Needle-punched geosynthetic clay liner (GCL) specimens subjected to up to 100 freeze-thaw cycles in the laboratory, and GCL samples recovered from the field after 3 years, are examined to assess their permeability with respect to both water and Jet A-1 fuel using flexible wall permeameters. The mean GCL hydraulic conductivity with respect to water is shown to be 3.3 x 10(-11) m/s before freeze-thaw. The mean hydraulic conductivities after up to 100 freeze-thaw cycles did not change significantly, and were in the range 2.2-5.3 x 10(-11) m/s. Freeze-thaw cycles did reduce the entry pressure required for Jet A-1 to begin to permeate through the GCL from about 27 to 55 kPa with no freeze-thaw cycles to 13.8-20.7 kPa for 3 to 50 freeze-thaw cycles, and to 0-13.8 kPa after 100 freeze-thaw cycles. For the GCL specimens subjected to 5, 12 and 50 freeze-thaw cycles in the laboratory, the hydraulic conductivity with respect to Jet A-1 is less than 3 x 10(-11) m/s at a pressure just above the entry pressure, compared with less than 3 x 10(-12) m/s for GCL samples recovered from the field. The combined effect of many freeze-thaw cycles and permeation with Jet A-1 did result in an increase in hydraulic conductivity; however, the effect was small, and the GCL performed well with a maximum hydraulic conductivity of 1 x 10(-10) m/s after 100 freeze-thaw cycles.