垃圾填埋场中泡沫诱发高气压形成机理及对堆体稳定影响研究

垃圾降解产生填埋气淤积在堆体内从而形成高气压，极易诱发堆体失稳流滑及填埋气扩散爆炸等环境灾害，以往将填埋气视为连通气会严重低估气压大小。申请人通过长期现场勘察发现部分填埋气以泡沫这种离散相气体形式存在，而目前关于填埋场中泡沫流研究尚属空白。本项目拟通过CT扫描测试、孔隙网络模型及微流控芯片试验研究泡沫在垃圾孔隙内的微观流动过程，采用垃圾柱驱替试验定量刻画泡沫与连通气在垃圾中宏观流动特性的差异。基于泡沫微观-宏观运移特性的研究，提出泡沫相对渗透系数krf与饱和度Sw的渗流本构关系，从而建立填埋场中含水、气、泡沫的三相渗流模型，模拟填埋场高气压带形成过程，并数值分析其对堆体稳定性影响。通过超重力模型试验再现高液气压力共同诱发填埋边坡失稳过程，研究边坡滑移模式并提出考虑高气压的稳定分析方法，为填埋场稳定性评估与灾害防控提供理论和实测依据。

Biodegradation of municipal solid waste (MSW) produces a large amount of landfill gas (LFG) to be trapped in the waste body, resulting in the formation of high gas pressure. It can easily cause environmental disasters such as slope failure, landfill gas diffusion and explosion. The assumption that LFG is a connected phase in MSW leads to underestimation of the gas pressure. The applicant finds that part of the landfill gas exists as foam in landfills through long-term site investigation. However, there are no reported studies on investigating foam flows in landfills. In this project, the CT scanning test, pore network model and microfluidic chip test are carried out to study the microscopic flow of foam in waste pores. The difference between foam flow and connected gas flow in waste is quantitatively characterized by the displacement test of waste column. Based on the study of the micro-macroscale flow behaviors of foam, the constitutive relation between foam relative permeability krf and saturation Sw is proposed, so as to establish a three-phase flow model with liquid, gas and foam in landfills. The model is used to simulate the formation process of high gas pressure, and analyze its influence on the slope stability of landfills. The process of slope failure induced by high liquid and gas pressures is reproduced by the hypergravity model test. The slope sliding mode is studied and the stability analysis method considering high gas pressure is proposed. The outcome from this project will provide theoretical and practical basis for the stability assessment and disaster prevention of landfill site.