Permeability, Pore, and Structural Parameters of Undisturbed Silty Clay Presented in Landfill Leachate
2020
Lu, Haijun | Wang, Chaofeng | Li, Dinggang | Li, Jixiang | Wan, Yong
This study focused on the permeability and structural evolution of impeded soil layers in landfill. A series of laboratory tests including a permeability test, X-ray diffraction, nuclear magnetic resonance, scanning electron microscopy, and laser particle size tests were conducted to analyze the permeability and microstructure characteristics of undisturbed silty clay polluted by landfill leachate. The hydraulic conductivities increased with time in the first 108 h. After 108 h, the hydraulic conductivities of undisturbed silty clay polluted by landfill leachate decreased. After 205 h, the changes in the hydraulic conductivity stabilized, and the hydraulic conductivity decreased with the increase of the concentration of leachate. The volume fractions of inter-particle and intra-aggregate pores were much higher than those of other pores. The optimal radius decreased as the concentration of leachate increased. The blockage of the pore channel and weakened permeability was caused by solid matter interception by the porous medium. As the height of the specimen increased, the volume fraction of coarse grain changed rapidly and sharply, and the volume fraction of fine grain changed slowly. The average particle size increased with increased specimen height and decreased as the leachate concentration increased. A comprehensive structural parameter (ζ) of undisturbed silty clay polluted by landfill leachate was obtained based on the test results. The equation of comprehensive structural parameter ζ of undisturbed silty clay polluted by leachate was established. These results can provide fundamental data for evaluating the stability of the underlying stratum of landfill sites.
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