Hydraulic conductivity of a dense prehydrated geosynthetic clay liner

ABSTRACT: Dense prehydrated geosynthetic clay liners (DPH-GCLs) are a particular type of GCL which, unlike conventional GCLs manufactured with dry bentonite, contain bentonite prehydrated during manufacturing. DPH-GCLs are produced by a patented process that includes bentonite prehydration with a polymer solution and vacuum extrusion. This paper describes the results of permeability tests that were carried out using flexible-wall permeameters to investigate the hydraulic conductivity of a DPH GCL to water, natural seawater and a 12.5 mmol/l CaCl2 solution. Moreover, the efficiency of the 0.1 m overlap seams between DPH-GCL panels has been investigated by means of a medium-scale permeameter able to accommodate specimens 0.305 m in diameter. Test results showed that the DPH GCL has very low hydraulic conductivity to water (10−12–10−11 m/s) and preserve low permeability, of the order of 10−11 m/s, in the presence of relatively high calcium concentration in the permeating liquid. However, the efficiency of overlap seams can be affected by the permeant type. In the presence of permeant liquids that inhibit swelling (e.g. seawater), the hydraulic efficiency of the seams needs to be improved by adding bentonite paste at the overlap interface. The hydraulic performance of the DPH-GCL is attributed to the combination of prehydration, densification and chemical amendment.