80 Waste Management & Research Waste Manage Res 2006: 24: 80–91 Printed in UK – all right reserved

Unsaturated consolidation theory for the prediction of long-term municipal solid waste landfill settlement The understanding of long-term landfill settlement is impor-tant for landfill design and rehabilitation. However, suitable models that can consider both the mechanical and bio-decomposition mechanisms in predicting the long-term land-fill settlement are generally not available. In this paper, a model based on unsaturated consolidation theory and consid-ering the biodegradation process is introduced to simulate the landfill settlement behaviour. The details of problem formu-lations and the derivation of the solution for the formulated differential equation of gas pressure are presented. A step-by-step analytical procedure employing this approach for esti-mating settlement is proposed. The proposed model can gen-erally model the typical features of short-term and long-term behaviour. The proposed model also yields results that are comparable with the field measurements