Effects of stress history on compressibility characteristics of undisturbed landfill waste material

Abstract

An extensive set of experiments were conducted in this study to evaluate the impacts of different levels of loading and unloading on compressibility characteristics of landfill waste materials. To achieve this purpose, a large undisturbed waste sample with a diameter of 250 mm was collected from a landfill site, in Sydney. The collected sample was composed of mainly construction waste, decayed organic material, wood, metal, plastic, glass, paper, and cardboard. A large diameter Rowe cell setup was utilised to saturate the undisturbed sample followed by multi-stage unloading and reloading consolidation and creep tests, lasting approximately 330 days. The testing data on the landfill waste were used to determine the compression and recompression indices, as well as the coefficient of consolidation and creep index. These experimental results demonstrate that the compressibility parameters of the collected landfill material significantly depend on the loading history, and in particular, the over consolidation ratio. The findings revealed that the stress history of the waste material has a significant effect on the primary settlement and its rate as well as the long-term creep rate. Thus, it is inferred that the application of the preloading method can improve the compressibility parameters and significantly reduce the post-construction consolidation and creep settlement of landfills.