This paper presents the findings of a settlement investigation conducted at a municipal solid waste landfill in Melbourne. As part of the study, data related to the characteristics of the landfill in terms of its waste composition, moisture content, density/porosity, daily covers, and biodegradation were also collected. The settlement data were fitted to an empirical (Sowers) model to determine long-term secondary settlement parameters related to the known landfill characteristics. They were then compared to values reported in the literature.
Compared with soils, the settlement mechanisms in municipal solid waste (MSW) landfills are complex (Sowers 1973, Edil et al. 1990, Wall and Zeiss, 1995). The waste fill has an inherent heterogeneity and anisotropic material properties that are more difficult to characterise than soils. These include compaction/density, daily cover, moisture content, composition, and biodegradation. The variations in these properties together with the unsaturated nature of most landfills have imposed certain limitations on the use of classical soil mechanics approaches to predict landfill settlements. Settlement prediction based on monitoring and observational procedures thus becomes a viable tool. While the literature has reported some field settlement observations, few studies attempted also to relate them to the above important associated landfill properties. This paper presents the findings of a settlement investigation conducted at a municipal solid waste landfill in Melbourne. This investigation formed part of a larger study conducted on a fully instrumented full-scale cell at the Lyndhurst Sanitary Landfill located 35 km south-east of the city. The objective of the project was to evaluate the full-scale landfill behaviour (including settlement), enhanced biodegradation promoted by leachate recirculation, and landfill hydrology. A full description of the research project was given by Yuen (1999). The settlement of the landfill has been monitored for about four years since final capping in January 1996.