Impact of leachate filtration on slope failure potential of landfill side walls

Abstract

The most common method for organized solid waste disposal, in middle and low income countries, is certainly the use of landfills. Although design of those structures has been improved significantly during the last decades, there are still potential hazards that require attention. In this paper, one of the many possible hazardous scenarios has been investigated. In the event of heavy precipitation leachate head is rising in the body of active landfill presuming there is no daily cover above the body. Due to leachate drainage malfunction, leachate head can rise above the design criteria value. With the landfill sidewall geomembrane previously damaged, or poorly built, gravity will drive the leachate through porous side walls of landfill. Gravity-driven groundwater flow will influence the distribution of effective stress in the body of a side wall. Effective stress, in turn, influences the potential for shear slope failure which can be quantified using the Coulomb failure potential. For evaluation of the effects of leachate filtration, we formulate a two-dimensional, steady state, poroelastic model. Steady state filtration model is formulated for unsaturated/saturated porous media. For the illustration, leachate flow field, total body force field and effective stress field are calculated in a landfill side wall. Based on this results Coulomb failure potential field is calculated for the body of a side wall. In most parts leachate flow significantly increases the value of the failure potential, while shifting the locus of greatest values towards the toe of the outer slope of a side wall.