Impact of differential settlement on leakage through geomembranes in waste covers

To quantify the effects of differential settlement on leakage through a geomembrane (GMB) hole in waste (landfill/mine tailings) covers, field experiments were conducted at Queen's University Experimental Liner Test Site on two sections, each with a 4H:1V slope. Over 13 months, measurements showed that a 3 m x 2 m x 0.12 - 0.17 m depression in Section B led to a 51-fold increase in leakage when compared to Section A, which had no such depression (493L vs 11.1 L). Notably, in Section B, 284 mm of precipitation between November and February resulted in 281 L of leakage, whereas 537 mm of precipitation between June and September led to a mere 142 L of leakage. A 3D numerical investigation provides encouraging agreement with the experimental measurements and confirms a counterintuitive 43% increase in leakage with a decrease in the temperature of cover sand from 21.9 degree celsius to 1 degree celsius, due to the influence of temperature-dependent viscosity on the hydraulic conductivity of the cover soil. This paper offers insights for optimizing waste cover design and inspection procedures to mitigate the challenges of contaminant control.