Time-dependent settlements in landfills

Estimation of time-dependent settlements is an essential component of the management and design phases of landfills. Reliable settlement predictions are needed to evaluate the remaining life of existing landfills, the integrity and functional ability of the cover caps, future vertical expansions, and the ultimate use of the landfill surface. Practicing engineers generally calculate time-dependent settlements in landfills using conventional geotechnical methods which include Terzaghi one-dimensional consolidation and secondary compression. However, time-dependent settlement in landfills is a complex process which involves not only mechanisms related to water flow and creep but also gas flow and biodegradation in both saturated and unsaturated media. In this paper, a conceptual model which includes the integration of four modes contributing to settlements is proposed. The conceptual model encompasses the development of standard laboratory and field procedures for obtaining the necessary constitutive parameters.