The effect of temperature and salinity on permeability and hydraulic conductivity evolution of clayey liners in solid...

Effective anti-seepage of landfill leachate relies on compacted clay liners (CCL) and geosynthetic clay liners (GCL). However, landfill biochemical degradation generates heat and salinity, affecting clay permeability. Previous studies lacked systematic analysis of their combined effects. This study experimentally investigates how temperature (5 ∼ 30 °C) and salinity (0 ∼ 20 g/L) jointly impact clay permeability, quantitatively analyzing mechanisms that temperature-dependent fluid viscosity, salinity-induced soil property changes on hydraulic conductivity, and their coupled influence on apparent permeability. Key findings: (1) At fixed salinities (1, 5, 10, and 20 g/L), 5 ∼ 20 °C caused slow apparent permeability rise at 1 ∼ 5 g/L but no significant effect at 10 ∼ 20 g/L. 20 ∼ 30 °C had notable effect, with permeability increasing rate decreases from 46.8 % to 6.6 % as salinity rises from 1 g/L to 10 g/L. (2) At fixed temperatures (20 and 30 ℃), apparent permeability and hydraulic conductivity declines with salinity: rapidly (0-5 g/L), slowly (5-10 g/L), and stably (10-20 g/L). (3) Temperature not only affects hydraulic conductivity, but also synergizes with salinity on bound water, thereby affecting apparent permeability. Temperature regulation involves adjusting the conversion threshold of bound water with salinity, and salinity affects the degree of change of bound water with temperature. 20 ℃ and 10 g/L salinity are the key thresholds in this study for regulating the temperature sensitivity of permeability and achieving stability with increasing salinity. Hydraulic conductivity models confirm that salinity-induced soil property and temperature-driven fluid property variations are key mechanisms controlling clayey liner hydraulic conductivity, providing support for developing long-lasting landfill anti-pollution clay barriers.