Stability of bioreactor landfills with leachate injection configuration and landfill material condition

In this study, the design factors of bioreactor landfill were investigated using the coupled leachate-infiltration and slope-stability analyses for various conditions of leachate injection, subgrade, and landfill waste. The factor of safety (FS) decreased with leachate injection where larger and faster reduction of FS was observed for higher injection pressure. The upper-placed injection pipes within landfill induced larger wet zone. The number of injection pipe indicated some effect on FS for the lower-placed case. The optimum location of injection pipes was at heights above Y/H = 0.33. The highest location of injection pipes should be identified considering landfill property and geometry conditions. Shallower and smaller slip surface within landfill was formed for strong subgrade whereas deeper, larger slip surface with lower FS was formed for soft subgrade. For low-compaction landfills, leachate injection reached the steady state and perched leachate was formed. The values of FS for high- and low-compaction cases were similar for soft subgrade indicating that the compaction of landfill waste does not affect the overall stability of landfill significantly for soft subgrades.