Overburden effects on waste compaction and leachate generation in municipal landfills

Abstract

This thesis presents a model to predict the effects of overburden pressure on the formation of leachate within municipal solid waste landfills. In addition, it estimates the compaction and subsequent settlement that the waste will undergo due to the force of material placed above it. The leachate model is based on a mass balance on water, expressed within finite elements constructed throughout the landfill. It incorporates the effects of gas generation, field capacity, and precipitation in determining the leachate produced within each element. The model then migrates this leachate through the landfill. The compaction routine utilizes Elastic Theory analysis to determine the forces which exist within the landfill due to overburden pressure. Empirical relationships are then used to calculate a level of compaction associated with these force, and the elements are deflected accordingly. The model is designed to be incorporated with a previously constructed gas generation and movement simulation, known as GasPro, which was developed by Stallard (1990) and an automatic gridding and filling scheme constructed by Beck (1994). Both the leachate production and the waste compaction portions of the model were found to be sensitive to the sequence in which the waste material was placed in the landfill.