Modeling Settlement in MSW Landfills: a Critical Review

Landfills remain an attractive disposal route for municipal solid waste because in most cases it is more economical than other alternatives such as incineration and composting. The post-closure development of landfilled areas becomes essential as urban growth reaches landfill boundaries. However, physicochemical and biological processes inevitably hinder the beneficial use of such lands because of gas and leachate generation coupled with significant settlement. The rate and magnitude of landfill deformations are often nonuniform resulting in differential settlements that can have devastating effects on the integrity of any structure erected on the landfill. Differential settlements also eventually result in problems such as surface ponding, development of cracks, and failure of the cover system, including tearing of geomembrane, as well as damage of gas collection and drainage pipes. The ability to predict settlement becomes a key issue in the design and construction of landfills. Numerous models have been developed to simulate the movement of solid waste. This article presents a critical review of such models, describes the applicability and usage of these models, and discusses the necessity to develop a multiphase, multicomponent comprehensive model integrating gas generation, leachate movement, and refuse settlement.