A constitutive model is developed to describe the stress–strain–time behavior for decomposing municipal solid waste (MSW) within a critical state soil mechanics framework. The model is an extension of the Modified Cam-Clay plasticity model. In this model, three sources contribute to the hardening of MSW due to volumetric strain: time-independent plastic volumetric strain, time-dependent volumetric mechanical creep strain, and time-dependent volumetric strain due to the biodegradation (decomposition) of MSW. The MSW model was evaluated through numerical analyses of large-scale one-dimensional compression tests in the laboratory and the field and the reported vertical and horizontal deformations of a MSW landfill. The associated model parameters were obtained by compositional analysis of the waste, from values reported in the literature, and by fitting numerical results to observed behavior. For the laboratory compression test, the best-fit numerical simulation over-predicted the early settlement but converged on the experimental values after 200 days. Initially, the calculated vertical strains in the field-scale test deviated from the measured strains by up to 10% over the 398-day period of the test. However, numerical results after adjusting model parameters to provide the best fit with the measured strains resulted in a maximum deviation of less than 3% over the test duration. The calculated vertical displacements of the MSW landfill were consistent with field measurements. However, the calculated horizontal displacements were significantly lower than the measured values. Sensitivity studies showed that the time-dependent settlement predicted by the model is highly sensitive to the biodegradation rate of MSW. The good agreement between numerical values and observed vertical deformations for the SWEAP section on the MSW landfill suggests that the model has the potential to assess the performance of subsystems in landfills (e.g., the performance of a side slope liner system subject to landfill settlement). However, the discrepancy between predicted and observed horizontal displacements suggests that the numerical model can be improved by incorporating deviatoric creep deformations in the constitutive model.

建立了本构模型来描述在临界状态土壤力学框架内分解城市固体废物（MSW）的应力-应变-时间行为。该模型是“改进型凸轮-粘土”可塑性模型的扩展。在此模型中，由于体积应变而导致MSW硬化的三个来源：与时间无关的塑性体积应变，与时间有关的体积机械蠕变应变和由于MSW的生物降解（分解）而引起的与时间有关的体积应变。通过对实验室和现场大规模一维压缩试验的数值分析以及所报告的MSW垃圾填埋场的垂直和水平变形，对MSW模型进行了评估。相关的模型参数是通过对废物的成分分析从文献中报道的值获得的，并通过将数值结果拟合到观察到的行为。对于实验室压缩测试，最佳拟合数值模拟高估了早期沉降，但在200天后收敛于实验值。最初，在398天的测试期内，现场规模测试中计算出的垂直应变与测得的应变之间的偏差最大为10％。但是，在调整模型参数以提供与所测应变的最佳拟合之后的数值结果导致在测试期间最大偏差小于3％。MSW垃圾填埋场的计算垂直位移与现场测量结果一致。但是，计算出的水平位移明显低于测量值。敏感性研究表明，模型预测的随时间变化的沉降对MSW的生物降解率高度敏感。在MSW垃圾填埋场的SWEAP部分，数值与观察到的垂直变形之间的良好一致性表明，该模型具有评估垃圾填埋场子系统性能的潜力（例如，受填埋场沉降影响的边坡衬砌系统的性能）。但是，预测的水平位移与观察到的水平位移之间的差异表明，可以通过在本构模型中纳入偏斜蠕变变形来改善数值模型。在MSW垃圾填埋场的SWEAP部分，数值与观察到的垂直变形之间的良好一致性表明，该模型具有评估垃圾填埋场子系统性能的潜力（例如，受填埋场沉降影响的边坡衬砌系统的性能）。但是，预测的水平位移与观察到的水平位移之间的差异表明，可以通过在本构模型中纳入偏斜蠕变变形来改善数值模型。在MSW垃圾填埋场的SWEAP部分，数值与观察到的垂直变形之间的良好一致性表明，该模型具有评估垃圾填埋场子系统性能的潜力（例如，受填埋场沉降影响的边坡衬砌系统的性能）。但是，预测的水平位移与观察到的水平位移之间的差异表明，可以通过在本构模型中纳入偏斜蠕变变形来改善数值模型。