垃圾填埋场沉降变形条件下气-水-固耦合动力学模型研究

基于多孔介质流气–水–固耦合和微生物降解理论,建立描述这一复杂动力学行为的二维气–水–固耦合数学模型,并给出耦合模型的数值格式。通过数值仿真实现垃圾填埋体的变形沉降及气体产生和迁移演化过程的可视化,得到气体压力及产气量随填埋年份的变化规律。数值计算结果表明:填埋体内总应力及孔隙度的改变与垃圾降解变化规律一致;抽气过程使场内气体压力得到释放;由于沉降作用填埋场内水相饱和度有增大的趋势,其中底部变化较顶部明显;此外,气井产量的变化与气体迁移单相模型的计算结果基本吻合,验证耦合模型的可靠性,其研究成果为垃圾填埋场沉降控制与气体资源化利用提供技术支持和理论依据。

A GAS-HYDRAULIC-SOLID COUPLING DYNAMICS MODEL UNDER LANDFILL SETTLEMENT

Landfill gas(LFG) and leaching solution are generated by bio-degradation in bioreactor landfills inducing the settlement of waste.The deformation and movement of waste matrix result from upper landfill loading and bio-degradation behaviour of organic matter.Based on porous medium fluid(water and gas)-solid coupling and micro-degradation theory,the gas-hydraulic-solid coupling model is developed to describe the dynamic behavior of settlement and LFG flow in landfill.And the finite element model is established.The visualization of matrix deformation and gas generation and transport is presented by numerical simulation.The variation of gas pressure and flow rate with time(year) elapsed after the closure of the landfill is given.The results show that the variation law of waste degradation is coincident with the total stress and porosity of landfill waste.The gas pressure is released by extracting within the landfill.The water saturation increases with the settlement,and the variation amplitude of saturation at the landfill bottom is more obvious than that at the top.The gas flow rate by coupling model agrees well with that by single phase model.The reliability of the coupling model is verified.It will provide technological and theoretical support for further studies on settlement treatment and gas resource reuse of municipal solid waste.