Xie Haijian, Fei Shuangke, He Haijie, Zhang An, Ni Junjun, Chen Yun
MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering, Zhejiang University, Hangzhou, 310058, China.
Center for Balance Architecture, Zhejiang University, 148 Tianmushan Road, Hangzhou, 310007, China.
Environ Sci Pollut Res Int. 2022 Nov;29(51):76944-76960. doi: 10.1007/s11356-022-21189-8. Epub 2022 Jun 7.
A field gas extraction experiment is carried out at a high-kitchen food large-scale landfill site with high leachate level. The leachate level was decreased to improve the pumping efficiency. Considering the heterogeneity of the municipal solid waste (MSW), the pores in the unsaturated MSW are divided into matrix pores and fractures. A transient dual-porosity model was then developed to analyze the pumping test results. The first and second boundary conditions considering the effect of cover layers of landfills was involved. The results show that the gas flow rate can be increased by 14-37% due to the drawdown of the leachate level. Compared with the single pore model, the dual-porosity model can better predict the field results, indicating that the preferential flow in the landfill caused by the heterogeneity of MSWs is very important. As the pumping pressure increases by a factor of 5, the ratio of fractures to pores w can be decreased by a factor of 4.4. This may be due to the fact that the fractures will be compressed when the effective stress was increased as the negative pumping pressure was applied. The pumping pressure and the anisotropy value of the MSWs have the greater influence on the well radius of influence. The proposed model can be used for effective design of the field gas pumping experiments. The obtained gas generation rate, gas permeability of the dual porosity MSWs can be useful for gas transport analysis and gas pumping well design for the high-kitchen food content landfills.
在一个渗滤液水位高的餐厨垃圾大型填埋场进行了一次现场气体抽提试验。降低了渗滤液水位以提高抽水效率。考虑到城市固体废弃物（MSW）的非均质性，非饱和MSW中的孔隙被分为基质孔隙和裂隙。然后建立了一个瞬态双孔隙模型来分析抽水试验结果。涉及了考虑填埋场覆盖层影响的第一和第二边界条件。结果表明，由于渗滤液水位下降，气体流速可提高14% - 37%。与单孔隙模型相比，双孔隙模型能更好地预测现场结果，这表明MSW非均质性导致的填埋场优先流非常重要。当抽水压力增大5倍时，裂隙与孔隙的比值w可减小4.4倍。这可能是由于施加负压抽水时有效应力增加，裂隙会被压缩。抽水压力和MSW的各向异性值对影响井半径有较大影响。所提出的模型可用于现场气体抽提试验的有效设计。得到的双孔隙MSW的产气率、气体渗透率可用于高餐厨垃圾含量填埋场的气体运移分析和抽气井设计。
