Abstract:

A series of swelling tests were carried out on bentonite and sand mixtures saturated by pure water and landfill leachate; the mixtures sported different sand mixing rates. The tests were carried out under various temperatures and a vertical pressure of50 kPa. Furthermore, the swelling tests were followed by consolidation and falling head tests to measure hydraulic conductivity. The following test results were obtained. (1) The liquid used for saturating the unsaturated soils significantly influenced the swelling characteristics of the bentonite and sand mixture. The final swelling rate of the mixtures saturated by the leachate was less than that of the mixtures saturated by pure water. (2) When the sand mixing rate was low, the swelling pressure of the mixture saturated by the leachate was smaller than that of the mixture saturated by water. When the sand mixing rate was 50%, the swelling pressures of the mixtures saturated by leachate and water were nearly identical. Moreover, the swelling pressures and final swelling rates of the mixtures increased with decreasing temperature. (3) For similar void ratios, the hydraulic conductivity of the mixtures saturated using water was slightly higher than that of the mixtures saturated using leachate. Furthermore, the hydraulic conductivities increased with increasing temperature. (4) For similar void ratios, the hydraulic conductivity measured via consolidation tests was lower than that measured using the falling head test.

Key words: bentonite and sand mixture, leachate, swelling, temperature, hydraulic conductivity