基于龄期影响的垃圾填埋体边坡稳定性分析

Stability analysis of landfills slope based on age influence

城市垃圾填埋场在填埋和运营过程中,垃圾土的抗剪强度会随着龄期增长而变化,其填埋体自身稳定性也会随之改变。先统计了国内外学者对垃圾土抗剪强度参数的分析,再对黏聚力和内摩擦角随龄期增长的变化情况进行整理归纳。在假定堆填体材料相近的情况下:随龄期增长,黏聚力呈现二次函数衰减趋势,内摩擦角呈现对数函数增长趋势;且在填埋10~15 a后,黏聚力趋近于0,内摩擦角增大了15°~25°。再建立分层垃圾填埋体模型,对各填埋层分别赋予与龄期相关的抗剪强度参数,最后结合PLAXIS有限元软件对垃圾填埋体进行了不同龄期下边坡稳定性分析。计算结果表明:稳定性安全系数随龄期增长呈现先减小再增大的趋势,位移主要集中在边坡中部,沉降主要集中在坡顶;垃圾填埋体在运营过程中,应着重关注边坡位移变化情况和封场后第10 a左右的填埋体安全性。研究结果对填埋场设计和现场安全性有明显的工程指导意义。

In the process of landfill and operation,the shear strength of municipal landfill will change with the increase of age,and the stability of landfill itself will also change.In this paper,the analysis of shear strength parameters of garbage soil by domestic and foreign scholars was made,and the variation of cohesion and internal friction angle with age increasing was summarized.If the material of the landfill is similar,the cohesive force tends to decay with quadratic function while the internal friction angle increases with logarithmic function;moreover,after 10—15 years of landfill,the cohesion approached zero and the internal friction angle increases by 15°—25°.Then a layered landfill model was established,and the shear strength parameters related to age were given to each landfill layer.Finally,PLAXIS finite element software was used to analyze the slope stability of landfill at different ages.The stability safety factor decreases first and then increases with the age increase.The displacement is mainly concentrated in the middle of the slope while the settlement is mainly concentrated in the top of the slope.During the operation of landfill,attention should mainly be paid to the change of slope displacement and the safety of landfill around 10 years after sealing.The research results have obvious engineering significance for landfill design and site safely.