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Hydraulic performance of Compacted Clay Liners (CCLs) under combined temperature and leachate exposures

A.A. Aldaeef, M.T. Rayhani
Waste management 2014 v.34 pp. 2548-2560
ambient temperature, chemical precipitation, exposure duration, hydraulic conductivity, landfills, physicochemical properties, tap water, viscosity
Experimental investigations were carried out to investigate the effect of thermo-chemical exposures on the hydraulic performance of Compacted Clay Liners (CCLs) in landfills. Hydraulic conductivity of most CCL specimens was increased by two to three times their initial values when exposed to 55°C for 75days. CCL specimens also experienced increases in their hydraulic conductivities when exposed to leachate at room temperature. This behaviour could be due to the decrease in viscosity when the permeant was changed from tap water to leachate. However, as the leachate exposure time exceeded the first 15days, hydraulic conductivity readings decreased to as much as one order of magnitude after 75days of leachate permeation at room temperature. The gradual decrease in the CCLs hydraulic conductivities was most likely due to chemical precipitation and clogging of pore voids within the soils which seemed to reduce the effective pore volume. The rate of hydraulic conductivity reduction due to leachate permeation was slower at higher temperatures, which was attributed to the lower permeant viscosity and lower clogging occurrence. The observed hydraulic behaviours were correlated to the physical, mineral, and chemical properties of the CCLs and described below.