填埋气体运移渗流场-应力场耦合模型及数值仿真

Study of seepage-stress fields coupling model and numerical simulation of landfill gas transport

基于流固耦合机制和多孔介质流体动力学理论,根据Landgem产气方程、气体状态方程,结合达西定律、有效应力原理,建立了渗流场-应力场耦合填埋气体运移模型。利用伽辽金方法对模型进行了离散,通过有限元方法对耦合作用下填埋气体压力分布规律进行了数值仿真分析,同时对垃圾填埋变形介质参数以及垃圾降解系数对填埋气体产气量影响进行了定量评价,表明耦合作用下抽气时孔隙结构发生改变,阻滞气体的运移,导致耦合作用较未考虑耦合作用的气体压力低。垃圾填埋气体的产气量小,对变形介质参数和降解系数的定量评价结果表明,垃圾填埋气体的产气量随着渗透系数和降解系数的增大而增加,因此耦合作用不能忽略。这不仅为准确控制气体的挥发与扩散以及气体资源的再利用提供可靠的理论依据,而且对于生态环境的保护和垃圾资源化利用具有重要的理论意义和实际应用价值。

Based on the theory of fluid-solid coupling and dynamics of fluids in porous media,and incorporated with the Landgem model,Darcy＇s law,state equation of gas,principle of effective stress,a seepage-stress fields coupling model of landfill gas transport has been established.Solutions to the coupled model are accomplished by finite element discretization.The numerical visualization simulation on the distribution law of gas pressure has been presented under coupling effect.The quantitative assessment to the effect of deformation media parameter and landfill degradation coefficient on landfill gas production has been analyzed.The results show that the gas pressure and gas yield in coupling action are less than uncoupling action,of which the reason is that the gas movement is blocked by changing of pore structures when pumping.And the production of landfill gas increase by the augmentation of permeability and degradation coefficient.Therefore,the effects of coupling cannot be ignored.The theoretical evidence is provided for forecasting migration and diffusion of landfill gas and preventing secondary-pollution.Moreover,it has important theoretical significance and practical use value for protecting ecological environment and resources utilization of landfill.