Settlement analysis of landfills under optimal decomposition conditions and case study

Estimation of the capacity and settlement for landfills is critical to the successful site operation and the future development of the sites.Different models and experimental results for the compression of municipal solid waste are analyzed and compared.It is indicated that the settlement induced by creep is relatively insignificant when the bio-degradation process is inhibited.The bio-decomposition model for calculating the settlement and estimating the capacity of the landfill under relatively optimal degradation conditions is improved and fulfilled.The model takes both the mechanical and degradation compressions into account and can be applied to analyze the settlement process of landfills with multi-step filling procedure,and is especially suitable for the optimal decomposition conditions.The parameters adopted in the model can be obtained by compression tests or referred to similar settlement record data.The model performance is assessed by simulating the variation of void ratio with depth.By further application to the Qizishan landfill,it is found that enhancing solid waste degradation during filling stage can considerably raise the capacity of the landfill and reduce the post-closure settlement potential.It is very difficult to reliably predict the post-closure compression process and ultimate settlement of a landfill by any model only according to short term settlement data if without taking the waste constitution,degradation conditions and filling procedure into account.