Impact of Pressurized Liquids Addition on Landfill Slope Stability

Abstract

The addition of liquids to municipal solid waste landfills, a practice sometimes performed under pressure to promote moisture distribution, has the potential to affect slope stability as a result of increased pore water pressure (and reduced shear strength) in the landfilled waste. Liquids addition into waste by using buried horizontal trenches was modeled to determine pore water pressure distributions, and the resulting effect on slope stability was assessed for different operational strategies. Model results using typical mechanical properties for solid waste found that pressurized liquids addition under a sloped landfill surface was possible without inducing a slope failure, providing liquids distribution was not obstructed. A reduction in the factor of safety occurred when simulating a poorly functioning leachate collection and removal system, a low-permeability cover layer within the landfill, a seepage control strategy using low-permeability soil, high liquids addition pressures, and waste permeability decreasing with depth. The sensitivity of the model results to input parameters was evaluated and graphically presented. The results demonstrate how pressurized liquids addition has the potential to affect slope stability and provide important insights for engineers charged with designing and permitting such systems.