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基于水分储存与释放机理的土质覆盖层在干旱和半干旱地区垃圾填埋场具有较好的应用前景。前人研究土质覆盖层大多侧重于其雨水存储及防渗性能,忽略了填埋气在覆盖层中的运移及其影响。通过在黄土土柱底部通入甲烷和二氧化碳等比例混合气体模拟填埋气在覆盖层运移,在土柱顶部施加3 cm常水头模拟雨水入渗对黄土覆盖层中气压分布以及各气体组分分布的影响。基于试验结果,利用商业软件Geo-Studio中的Air/W模块对黄土覆盖层水–气耦合运移进行了数值模拟与分析。研究结果表明:模拟雨水入渗降低了上层黄土的导气系数,导致土柱中气压显著增加,呈现出先增加至“突破值”然后回落至“稳定值”;气压“突破值”约等于上部土体进气值;数值模拟能较好地模拟水分入渗过程并捕捉到气压变化趋势,但由于其无法模拟多组分填埋气在土柱中的复杂物理过程,导致气压的模拟结果与实测值存在差距。本文为更准确模拟分析土质覆盖层中水与填埋气耦合运移过程提供了一些建议。
Soil cover based on the mechanism of water storage and release has better application prospects in arid and semi-arid landfills. Previous studies of soil cover mostly focus on the storage and seepage control of rainwater, neglecting the migration and influence of landfill gas in cover. Simulated the migration of landfill gas through the mixed gas of methane and carbon dioxide at the bottom of loess column, simulated the infiltration of 3 cm water head at the top of soil column to simulate the pressure distribution in the loess cover and the distribution of each gas component The impact of distribution. Based on the experimental results, Air / W module in commercial software Geo-Studio was used to simulate and analyze the water-gas coupling and migration of loess overlay. The results show that: the infiltration of simulated rainfall reduces the air conduction coefficient of the upper loess, resulting in a significant increase of air pressure in the soil column, showing an increase to “breakthrough” and then to “stable”; “air pressure” breakthrough "Is approximately equal to the intake value of the upper soil. Numerical simulation can better simulate the process of water infiltration and capture the trend of pressure variation. However, due to its inability to simulate the complicated physical processes of multi-component landfill gas in the soil column, There is a gap between the simulation results of atmospheric pressure and the measured values. This paper provides some suggestions for more accurately simulating the coupling process of water and landfill gas in soil cover.