垃圾堆体沉降对填埋气体收集效能的影响

The influence of landfill settlement on the efficiency of landfill gas collection

为分析填埋场上覆载荷引起的变形沉降以及垃圾自身降解作用对气体迁移特性的影响,采用多孔介质气-固耦合和生物降解理论,构建了填埋气体迁移的H-M耦合模型,通过数值模拟方法分析有无载荷作用对填埋气体储存及迁移规律的影响。结果表明:考虑载荷作用时,底部气体的压力值明显高于顶部,且底部与顶部气体压力差值的变化趋势较无载荷作用时更明显;随着填埋年限的增加,填埋场内部气体压力逐渐降低;考虑载荷作用时场内气体压力值高于不考虑载荷作用的情况,封场1a后二者气体压力差值为0.045 kPa,但10 a后压力差值达0.346 kPa;考虑载荷作用时气井收集量比不考虑载荷作用时高14.8%;载荷的作用在一定的程度上增大了抽气井影响半径的辐射范围。因此,上覆载荷引起的沉降变形对垃圾填埋气体的收集量影响显著,在设计填埋气体收集控制系统时应考虑该因素。

The influence of deformation settlement of landfill resulting from overlying loan and garbage degradation on the migration characteristics of landfill gas is analyzed in this study. The theories of porous medium gas-solid coupling and biodegradation were applied to construct an H-M coupling model of landfill gas migration so as to analyze the influence of the presence of loading on the storage and migration of landfill gas by the numerical simulation method. The results show that the pressure value of bottom gas with overlying load is clearly higher than the ones of top gas, and the change of gas pressure differences between the bottom and the top with overlying load is clearer than that of no load. With increasing landfill time, the gas pressure of landfill gradually reduces. The gas pressure of landfill with overlying load is higher than that of landfill with no load, and the difference of gas pressure between them is 0.045 kPa after the closure of landfill for one year,and 0.346 kPa after the closure of landfill for ten years. Collection amount of gas well with overlying load is higher 14.8% than that of with no load. The overlying load increases the radiation range of influence radius of the extraction well at some degree. The deformation settlement of landfill caused by overlying load can significantly influence the collection amount of landfill gas. This factor should be considered in the design of the control system of landfill gas collection.