Problems and solutions for GCLs used in waste containment facilities: temperature concerns and polymer treatment related to GCLs used in waste containment areas

Abstract

In this study, first, various geosynthetic clay liner (GCL) application areas were briefly defined and afterwards, the details of GCL usage in mine applications were given. GCLs are barrier materials that are preferred in mining facilities such as heap leach pads, tailing dams or waste landfills. In these applications, GCLs might be in contact with aggressive leachates that could deteriorate the hydraulic properties of the GCLs. The hydraulic capability of the GCLs is decreased by an increase in hydraulic conductivity or a decrease in swell index of the bentonite component of the GCL. Due to the biodegradation of the organic substances in a waste containment area, heat is generated and the temperature of the leachates increases. To investigate the effect of temperature, triaxial permeability and free swell tests were conducted on the GCLs that were permeated with 0.5 M MgCl2 solution and deionized water. The temperature of the permeation fluid was chosen as 20 and 40 °C. Furthermore, a cationic polymer having 1 and 2% amounts of mass was added to the bentonite component of the GCL to enhance the hydraulic capability of the GCL. Test results indicated that temperature increase in 0.5 M MgCl2 solution from 20–40 °C caused both an increase in the swell index and the permittivity of the GCLs. The increase in permittivity could be attributed to the lower viscosity of the fluid at higher temperatures. Finally, adding a cationic polymer up to the amount of 2% by mass to the bentonite resulted in almost two orders of magnitude decrease in the permittivity of the GCLs that were permeated with 0.5 M MgCl2 solution. In conclusion, cationic polymer-treated GCLs might be used effectively in waste containment facilities by both decreasing the permittivity and increasing the swell index of the GCLs.