Study On The Permeability And The Permeable Mechanism Of The Municipal Solid Waste

To investigate the permeability and the permeability mechanism of fresh municipal solid waste(MSW), a series of constant head permeability experiments were carried out by using two different of large-scale permeability model slot test apparatuses in the geo-environmental laboratory.According to the major composition of MSW samples from the Tianziling landfill in Hangzhou,China, fresh MSW testing sample. Three mixture proportions of samples were adopted and different of initial density were selected for each mixture proportion. The above experiments had been carried.Besides, the theoretical and analysis also been done.The fresh MSW was divided into three parts which were easily biodegradable material,difficultly biodegradable material, unbiodegradable material. Three mixture proportions were used to simulate the three stages of urban economic development those were underdeveloped, developing,and developed. The initial density of the samples were selected as 0.5、0.6、0.7、0.8、0.9、1.0 and1.1g/cm3 were prepared to investigate the vertical and horizontal permeability test.Based on the horizontal permeability test, following conclusions had been gained for the MSW.Permeation rate increases with increasing of the saturation degree of the fresh MSW, the relationship can be formulated as a polynomial function, and the fitted coefficients are greater than0.99; Permeation rate decreases gradually with the increasing of the initial density of the fresh MSW,the relationship can be formulated linear line, and the fitted coefficients are greater than 0.99; The relationship of the initial density and the permeability coefficient can be formulated linear line, the formulate can be used in the prediction the permeability coefficient of the newly landfill; Three mixture proportions of samples were adopted and the initial density ρ=1.1g/cm3 were selected for the long time the permeability test. The different Relationship between permeability coefficient of MSW and time can be formulated by exponential model, and the fitted coefficients are about 0.80.The range of the permeability coefficient of the fresh MSW is obtained, which ranges from 10-3cm/s to 10-2cm/s.Furthermore the following conclusions had been drawn for the vertical permeability test.The permeation rate and seepage and the initial density of MSW having the correlation, the permeate speed rate of saturated sample increases with the permeation rate increasing in the same initial density sample, this correlation following Darcy’s Law. The permeation rate decrease gradually with the increase of the initial density of the fresh MSW. The critical hydraulic gradient were found to increase with the initial density, the critical hydraulic gradient of different mixtureproportions MSW and the content of organics having the proportional, the range of the permeability coefficient were found to decrease with the increase of the content of organics.The permeability coefficient of three mixture proportions of samples is: The first permeability coefficient of the mixture proportions of sample is k=9.7×10-4~8.22×10-3cm/s, the second of that is k=1.19×10-3~1.02×10-2cm/s, the third one is k=1.59×10-3~ 1.17×10-2cm/s. The permeation rate decreases gradually with the increasing of the initial density of the fresh MSW, the changing of the porosity and the composition of MSW is the main reason of the permeability coefficient changing. The range of the permeability coefficient of the fresh MSW have a relationship with the mixture proportions of samples, the range of the permeability coefficient were found to decrease with the increase of the content of organics.The testing results show that the size effect of test apparatuses having a influence of the fresh MSW, the vertical permeability test apparatuses had more effected than that of horizontal one, the permeability coefficient of the same mixture proportion MSW having a same changing trend, the results can be provided reference for seepage analysis in landfill.