适宜降解条件下填埋场的沉降模型及案例分析

Settlement analysis of landfills under optimal decomposition conditions and case study

填埋场的沉降和容量分析对其填埋期及封场后的运营有着重要意义。综合比较了不同的填埋场沉降分析模型,总结了各种填埋体压缩试验和现场沉降监测结果。如果生物降解被抑制,蠕变引起的压缩量相对较小,大部分力学压缩将在较短时间内完成;完善并改进了生物降解压缩模型,并通过案例分析与现场孔隙比沿深度的变化进行了比较。该模型能用于描述常压力下的试样压缩,也能分析分层堆填填埋场的容量分析和封场后沉降,尤其适用于降解条件适宜的情况。模型中采用的参数可以通过压缩试验或反分析沉降资料的方法获得。通过案例分析发现,改善填埋期间填埋体的降解条件能够有效地提高填埋场的容量,减少封场后沉降的潜力。如果不考虑填埋过程、填埋高度、初始有机质含量、填埋场降解条件,即使有了一定的沉降观测资料,单纯采用经验公式去分析封场后沉降也并不合理。

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.