Study On The Shear Strength Of Municipal Solid Waste Consider The Moisture Content And Landfill Age

Due to the accelerated urbanization process,the urban population has increased significantly,and the production of municipal solid waste is increasing.As waste continues to be added to landfills and the height of the pile increases,the slope becomes steeper.With the increase in landfill age,the proportion of components will change greatly,thus affecting the stability of landfill,and large-scale sliding failure may occur in the middle of the landfill and the late sealing period.For the many landfills that have adopted bioreactors,the moisture content of municipal solid waste also increases during leachate recharge.The strength characteristics of municipal solid waste are very important for the design and operation of landfill and landfill accidents can also be effectively prevented and controlled.However,there are relatively few studies related to the relationship between municipal solid waste shear strength parameters,landfill age,and moisture content.In this study,samples of municipal solid waste from a waste landfill in Xi’an,China were collected through on-site drilling.In the environmental geotechnical laboratory,we conduct wet unit weight test,composition test,moisture content test,specific gravity test,particle analysis test,organic matter test,and field moisture capacity test.Considering the effects of six normal stress(25,50,100,150,200,and300 k Pa),nine landfill ages(1,2,3,11,12,13,21,22,and 23 y)and six moisture contents(natural,20,40,60,80,and 100%),324 groups of municipal solid waste were tested in the laboratory using a direct shear test apparatus.The results of the basic characteristics of municipal solid waste show that:(1)The wet unit weight of municipal solid waste range was 7.65–13.5 k N/m~3,and wet unit weight increases with an increase in landfill age.(2)Low-age municipal solid waste has a higher plastic content.As the landfill age increases,the amount of plastic content decreases and soil content increases.(3)The main distribution range of the moisture content of municipal solid waste is30–50%,and the natural moisture content of municipal solid waste does not appear to have a significant relationship with landfill age.(4)The specific gravity range of municipal solid waste was 1.512–2.338,and specific gravity increases with an increase in landfill age.(5)With the increase of landfill age,the proportion of small-size materials of municipal solid waste increased.(6)With an increase in landfill age,the organic materials of municipal solid waste gradually decomposed and the field moisture capacity of municipal solid waste decreases.The results of the direct shear test of municipal solid waste show that:(1)With an increase in horizontal shear displacement,the shear stress of municipal solid waste gradually increases without a peak stress phenomenon,which is a displacement hardening curve.(2)With an increase in landfill age,the cohesion decreases of municipal solid waste and the internal friction angle increases,and the shear strength of municipal solid waste increases.(3)With an increase in moisture content,the cohesion and internal friction angle of municipal solid waste increases,and the shear strength of municipal solid waste increases.The experimental data in this paper are compared and analyzed with those of related references,and the shear strength characteristics of municipal solid waste are discussed.The results of this paper can provide references for the design,operation and stability analysis of landfills.