应变硬化垃圾堆体抗局部沉陷研究

Study on local subsidence resistance of strain-hardening municipal solid wastes

通过三种不同材料堆体的局部沉陷模型试验发现局部沉陷条件下应变硬化材料可能产生"自支撑"现象。利用模型试验和退化情况下的解析解验证了数值分析模型模拟应变硬化材料堆体局部沉陷问题的有效性。在此基础上比较了采用不同垃圾应力应变模型的分析结果,考虑堆体材料应变硬化的复合指数模型和线弹性模型计算得到的沉陷区土压力明显小于与之对应的摩尔-库伦模型计算结果,采用传统摩尔-库伦模型计算得到的沉陷区衬垫系统挠曲变形和应变值偏大,因而针对砂土材料的Giroud(1990)Trapdoor土拱效应理论应用于垃圾堆体局部沉陷分析时存在一定的局限性。进一步分析了各种参数对衬垫系统表面土压力和变形的影响,发现沉陷区衬垫系统最大挠度和最大应变随垃圾堆体高度的增加而增加,随垃圾堆体模量和加筋体刚度的增加而减小。最后提出应变硬化垃圾堆体在局部沉陷条件下衬垫系统土工膜的应变计算和加筋层的设计方法,对于垃圾填埋场衬垫系统抗局部沉陷设计具有一定的指导意义。

The fact that the strain-hardening fill under local subsidence conditions may self-support was found by using trapdoor model tests for three different filling materials. The effectiveness of the numerical analysis model to simulate the strain-hardening fills under local subsidence conditions was verified by model test results and Finn （1963） analytic solutions. Analysis results using different Municipal Solid Waste （MSW） strain-stress models were compared. The calculated soil pressures on the subsidence area using the strain-hardening models such as the composite exponential model and the linear elastic model are significantly less than the corresponding results using the Mohr-Coulomb model, deflection and strain of the liner system on the subsidence area calculated by the traditional Mohr-Coulomb model are much larger. As a result, the application of the trapdoor soil arching theory of Giroud （ 1990 ） to analyses of local subsidence problems of MSW would be limited. Some different factors influencing both soil pressures on the liner system and deflection of the liner system were further investigated, it shows that both maximum vertical deflection and maximum strain of the liner system increase with the increase of MSW height, while decrease with the increase of MSW modulus and reinforcement tensile stiffness. Finally, a method for strain calculation of the geomembrane and reinforcement design resisting local subsidence in landfills was proposed, which may be applicable for design of landfill liner systems resisting local subsidence.