Numerical Simulation Of Uneven Settlement Of Municipal Solid Waste Landfill By FLAC 3D

With the rapid development of economy,the ever-increasing amount of waste output brings about serious pollution problems,so finding a green and economical solution is the key.At present,most of the cities in China still prolong the technology of sanitary landfill in the last century to dispose of rubbish.However,there are still various deficiencies in the establishment of a standardized urban landfill at this stage,for example,calculation of rubbish volume expansion rate,internal flammable gas collection,leachate treatment,the eventual closure of the cover,the uneven size of the settlement of the re-use of the problem and so on.At present,the accurate calculation of uneven settlement of landfill is the most concerned and the most outstanding problem for scholars at home and abroad..This paper calculates the settlement of Suzhou Landfill(Phase I)using the standard calculation method of landfill settlement and FLAC 3D numerical simulation.Based on the comparison with the actual settlement data,the paper introduces the calculation of Nanshan landfill in Jinzhou Subsidence and non-uniformity after closure,and give the main factors affecting the settlement calculation of landfill.In calculating the settlement of landfill,the geotechnical parameters of landfill soil with age were obtained by field drilling experiments.The parameters can reflect the characteristics of soil organic matter in different biodegradation stages.Finally,The iterative simulation obtains the non-uniform settlement within 20 years of the closure period,and obtains the following main conclusions:(1)When using the canonical method to calculate the settlement of Suzhou Landfill(Phase I),the main settlement increases with the increase of burial depth,and the ratio of the main settlement to the calculated height changes from the initial 2.4%to about 20.7%While the subsidence is divided into landfill period and closure stage,the ratio of subsidence to calculated height during landfilling changes from the initial 7.8%to about 17%.Subsidence after closure is 7.63m,which is 7.79%of the initial landfill height.The final total landfill settlement is 45.53%of the initial landfill height,and the total subsidence is slightly higher than the main subsidence.(2)When using FLAC 3D to simulate the landfill and sealing settlement of Suzhou landfill(Phase I),the ratio of landfill settlement size to actual landfill height of 94.91m during the landfill period reached 45.96%The ratio of the settlement of 6.17m to the actual landfill height of 46.91m before sealing was 13.15%,the settlement nonuniformity was large all around,the middle nonuniformity was low,the maximum settlement nonuniformity was about11%,and the landfill performance for the dome shape.(3)When using FLAC 3D to simulate the settlement of landfill stage of Nanshan landfill in Jinzhou,the subsidence gradually increases with age,but the rate will be more and more moderate.The maximum subsidence after 20 years of closure will reach 9.11m,Which is15.71%of the maximum elevation.However,the nonuniform sedimentation rate of the slope at the four locations of the landfill is larger,the maximum uneven settlement angle reaches 45~°,and the middle position is smaller and approaches 0~°.(4)The settlement of the landfill is related to annual landfill height and velocity.The final subsidence after closure is related to the organic matter content and stratification.The uneven subsidence rate has a great relation with the compaction status of the landfill when the landfill is closed.It is suggested that the landfill should be flattened and paved before the final closure.