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A eld gas extraction experiment is carried out at a high-kitchen food large-scale land ll site with high leachate level. The leachate level was decreased to improve the gas extraction e ciency. Considering the heterogeneity of the municipal solid waste (MSW), the voids 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 rst and second boundary conditions considering the effect of cover layers of land lls was involved. The results show that the gas ow rate can be increased by 14%-25% due to the drawdown of the leachate level. Compared with the single pore model, the dual-porosity model can better predict the eld results, indicating that the preferential ow in the land ll caused by the heterogeneity of MSWs is very important. As the pumping pressure increases by 5 times, the ratio of fractures to pores w f can be decreased by 4.4 times. 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 in uence on the well radius of in uence. The proposed model can be used for effective design of the eld 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 land lls.

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No abstract

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 gas extraction efficiency. Considering the heterogeneity of the municipal solid waste (MSW), the voids 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%-25% 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 5 times, the ratio of fractures to pores wf can be decreased by 4.4 times. 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.