| Rapid urbanization has led to an increased year-on-year waste output.How to effectively reduce,reuse and harmless treatment of Municipal Solid Waste(MSW)has been a hot topic for researchers.In order to make up for the shortcomings of traditional waste treatment methods,Tianziling landfill in Hangzhou China,first introduced Germany’s Mechanical Biological Treatment(MBT)technology as a pilot project for the treatment of Hangzhou Tianziling waste,the processed product is called MBT waste.Compared with the fresh municipal solid waste,the physical and mechanical properties of MBT waste have changed significantly.When MBT is landfilled,the design and operation of MBT landfill cannot be analyzed by the physical and mechanical characteristics of traditional municipal solid waste.Due to the lack of research on MBT waste in China,there is no design code and standard for MBT landfill.If the landfill is piled up randomly,it is easy to cause disastrous consequences such as uneven settlement and landslides of the landfill,and at the same time,it will bring serious economic loss and ecological pollution.So it is very important to study the physical and mechanical properties of MBT waste.This paper have studied the compression characteristics of MBT waste,supported by the National Natural Science Foundation general program "Research on strength characteristics and strength characteristics of municipal solid waste based on MIBT technology"(51678532)and”Research on correlation and interaction mechanism of MBT permeability and deformation"(51978625).Based on the study of the physical characteristics of MBT waste,such as composition,particle,moisture content,specific gravity and so on,a series of laboratory compression tests were carried out on MBT waste.The compression characteristics of MBT waste and the rebound characteristics after unloading were studied by considering the components of waste,load,sample size,saturation,compression time,temperature and other factors.Finally,according to the compression curve and the summary of the existing literature,the unsaturated long-term compression calculation model of MBT waste is obtained.The results show that:1.Physical test(1)MBT waste is mainly composed of paper,rubber plastic,textiles,wood,ceramic rubble,glass,metal,soil and indistinguishable materials,and the percentage content of rubber plastic component in MBT waste is the largest,while the percentage content of paper is the lowest.(2)The nonuniformity coefficient Cu of MBT waste is greater than 5,the curvature coefficient Cc is between 1 and 3,and the gradation is good.The moisture content of M1 and M2 is 20.21%and 15.41%respectively,and the specific gravity is 1.58 and 1.38 respectively.2.Compression test2.1 Multistage short-term compression-rebound test:(1)The immediate compression time of MBT waste is close to 24 hours.(2)In the multistage rebound compression test,the relationship between the void ratio and the logarithm of the load in the compression and rebound stage is in accordance with the first-order function.(3)The primary compression index Cc of MBT waste were 1.001,0.986;and the modified primary compression index C’c of MBT waste were 0.223,0.251.(4)The compression coefficient a and compression moduli Es are affected by the stress range.(5)The compressive strain of MBT waste mainly consists of plastic deformation and negligible elastic deformation.2.2 Single stage short-term compression test:(1)The relationship between the logarithm of compression time and the compression strain in the process of compression of unsaturated and saturated samples accords with the first-order function.(2)The compressive strain of unsaturated and saturated samples is a composite function of pressure P and time t.But the compressibility of the saturated sample is greater.2.3 Single stage long-term compression test:(1)The long-term compression process can be divided into immediate compression stage,mechanical creep stage and bio-induced compression stage.The immediate compression stage is mainly caused by the applied load,the mechanical creep is caused by the creep effect,and the bio-induced compression stage is mainly caused by the degradation of organic matter components in MBT waste.(2)The coefficient of secondary compression C’ac obtained in this paper is 0.022 and 0.015 respectively.The secondary compression coefficients C’ab in the bio-induced compression stage of MBT waste samples obtained in this paper are 0.174 and 0.127,respectively(3)The relationship between compression coefficient and temperature is shown as follows:in the stage of mechanical creep,the coefficient of secondary compression C’ac increases slightly with the increase of temperature,while in the stage of bio-induced compression,it increases rapidly,and the relationship between C’cb and temperature can be expressed by exponential model.(4)The compression of MBT waste is very little affected by the size,which can be ignored.(5)According to the test results and literature summary,the single-stage long-term compression calculation model of unsaturated MBT waste is obtained.In this paper,the compression characteristics of MBT waste and the rebound characteristics after unloading are studied by considering the components of waste,loading mode,sample size,saturation,compression time,temperature and other factors.Based on the compression characteristic parameters of MBT waste,the unsaturated long-term compression calculation model of MBT waste is obtained.The results can provide reference for settlement prediction and storage capacity estimation of MBT landfill. |
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