| To investigate the relevant characteristics of compression and permeability of fresh municipal solid waste with process of the gradually filling,large numbers of the compression and permeability combined tests had been carried out.According to the major composition of municipal solid waste samples from the Tianziling landfill in Hangzhou,China,fresh municipal solid waste testing samples were prepared in geo-environmental laboratory.Besides,the theoretical analysis had also been done.The fresh municipal solid waste was divided into three parts which were difficultly biodegradable material,unbiodegradable material and easily biodegradable material.Three mixture proportions of samples were adopted.Six different vertical pressures which were 25,50,100,150,200 and 300 kPa were selected,and six compression times for every vertical pressure were 0,1,2,6,12 and 24 hours in the compression process.Besides,six hydraulic gradients which were 2.0,1.75,1.5,1.25,1.0 and 0.5 were adopted in the permeability process,while five hydraulic gradients which were 5,4,3,2 and 1 were adopted when the vertical pressure is 300 kPa.111 municipal solid waste samples,648 compression and permeability combined tests were used to investigate relevant characterists of compression and permeability.The compression testing results show that:?1?With the increasing of the compression time,the density presents a growth trend.The density and the logarithmic compression time can be fitting with linear relationship,and most of the fitted coefficients are greater than 0.90;?2?With the increasing of the vertical pressure,the density presents a growth trend.The relationship between the logarithmic density and the vertical pressure can be fitted to linear line,and the fitted coefficients are greater than 0.92;?3?The contents of biodegradable materials have a great influence on the compressibility of fresh municipal solid waste;The compression and permeability combined testing results show that:?1?Critical hydraulic gradient is existed,and the water can permeate through the test sample only when the hydraulic gradient exceeds the critical hydraulic gradient.The relationship between the permeation rate and the hydraulic gradient can be formulated as a linear line,and the fitted coefficients are greater than 0.99,this correlation following Darcy's Law;?2?The permeation rate is reduced gradually along with the increasing of vertical pressure.The relationship between the logarithmic permeation rate and the pressure can be formulated by a line model;?3?The permeation rate is reduced gradually along with the increasing of compression time.The relationship can be fitted to a line model;?4?The permeability coefficient is reduced gradually along with the increasing of vertical pressure.The relationship between the logarithmic permeability coefficient and the pressure can be formulated as a linear line;?5?The permeability coefficient is reduced gradually along with the increasing of compression time.The relationship between the logarithmic permeability coefficient and the compression time can be fitted to the form of an attenuation model;?6?The permeability coefficient is reduced gradually along with the increasing of density.The relationship between the logarithmic permeability coefficient and the density can be formulated as a linear line;?7?The permeability coefficient is reduced gradually along with the increasing of compressive strain.The relationship between the logarithmic permeability coefficient and the compressive strain can be formulated as a linear line;?8?The range of the permeability coefficient of the fresh municipal solid waste is obtained,which ranges from 10-5 cm/s to 10-2 cm/s.Considering the impact factors of the vertical pressure,compression times,density,compressive strain and hydraulic gradient in the geo-environmental laboratory,the research results are closer to the landfill site actual situation,and the test results can be reference for the permeability analysis of the municipal solid waste landfill. |
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