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

Abstract

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 × 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 × 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 × 10–11 m/s at a pressure just above the entry pressure, compared with less than 3 × 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 × 10–10 m/s after 100 freeze–thaw cycles.