| Landfills are the most widely used method for municipal solid waste（MSW）disposal method in China.The degradation and stabilization of landfilled MSW is a complex and long-term process of biological and physicochemical reactions,resulting in a large amount of landfill gas left in the MSW,which is very easy to induce environmental disasters such as landslide and‘piping’.Further study of microbial community diversity and liquid-gas flow can improve the ability of disaster prevention and control in landfills.Therefore,the core of this study is the microbial community structure of MSW and the multi-phase flow in landfills considering the characteristics of pore structure（dual-porosity）and fluid properties（foam）.Based on previous studies,this paper aims to（1）Investigating the microbial community structure of landfills by high-throughput sequencing,and predict the relative abundance of functional genes;（2）Configure artificial solid waste and test its basic geotechnical characteristics.Monitoring the dynamic change of pore gas pressure and pore water pressure during foam or liquid-gas displacement by improved pore pressure sensor;（3）Constructing the model slope with the artificial MSW and sand to study the effects of injected gas on the pore-gas pressure,pore-water pressure,soil pressure and slope instability;（4）Bulding the mathematical model of dual porosity considering foam flow to simulate the high pore-gas pressure distribution of landfills.The main conclusions of this study are as follows:（1）Firmicutes,Bacteroidota,and Thermotogota were the dominant bacteria phyla in landfills.Defluviitoga,hydrogenispora,lentimicrobium,and caldicoprobacter were abundant in MSW samples;Methanothermobacter,and methanomassiliicoccus,which had the highest relative abundance in archaea,only used H2/CO2 to produce CH4.Metabolic function genes still accounted for a relatively high proportion in aged MSW,and most metabolic pathways were related to carbohydrate metabolism,amino acid metabolism and energy metabolism.（2）The test of the basic characteristics of artificial MSW,including water content,bulk density,void ratio,particle gradation,permeability and strength characteristics showed that the artificial MSW configured in this test is close to real MSW.Based on the high pressure range（30～200 k Pa）pore gas pressure sensor developed jointly,the pore gas pressure in the displacement process was successfully tested.The steady pore air pressure obtained by foam flow was about 180 k Pa,which was significantly higher than the limit pore gas pressure 64 k Pa in the process of water-gas displacement.（3）The mass model experiment showed that the gas（or foam）injection lead to high pressure and last for a long time and formed landslide and‘piping’.The foam sprayed on the toe of the slope,and the shear-slip occurred on the top of the spout area.The pore gas pressure at the time of failure reached 0.8～1.5 times of self weight stress.（4）Numerical simulation showed that the dual-porosity model considering foam seepage could simulate the high gas pressure distribution of landfill.The results showed that the existence of foam leads to further reduction of relative permeability of gas phase,increasing the peak value and duration of high gas pressure,which affects the stability of the slope. |
