Study On Fly-ash Modified Loess As Landfill Liner

With the increase of people's living standard, the emission of municipal solid waste is increasing with each passing day. Hence, the sanitary landfills technology as a method of final disposal of waste has been widely used. Leachate of landfill has high concentration and complicated composition, which caused serious harm to surrounding environment of landfill site as well as underwater. The liner system plays an important role on protecting the underwater. At present, synthetic materials are mostly used for landfill in order to meet the liner requirement in loess area as the natural ones can not meet the requirement. A lot of researcher modified the natural material to seeking something which are accord with the standard requirement. At the present time, studies on liner are mainly focused on modification of clay, there are almost not researches that based on the Ma Lan loess which is special in loess area foundation layer as the bedding course.Based on the engineering practice, this paper modified Ma Lan loess with fly-ash and adopted landfill leachate from landfill of Lanzhou as the permeable liquid. Through compaction test and permeability test, the hydraulic conductivity of loess under the maximum dry density was determined. Simultaneity, the changing regularity of hydraulic conductivity in natural loess, compacted loess and fly-ash modified loess were mainly discussed and the feasibility of loess and fly-ash modified loess used as the liner of landfill and the optimal proportion relationship between them were primary analyzed.The experiment results show that the hydraulic conductivity of the natural loess with leachate is less than 1.0×10^-5cm/s,but it cannot be used as the protection layer of landfill, even more to be the liner of landfill as its compactness cannot meet the need of requirement; The hydraulic conductivity of the compacted loess with leachate is between 1.0×10^-5 cm/s and 1.0×10^-7 cm/s, it can be used only as the protection layer. The hydraulic conductivity of compound soil, in which the content of fly ash is 10%, could be less than 1.0×10^-7cm/s,it can be used as the landfill liner.The hydraulic conductivity of soil samples are affected by many kinds of factors such as void-ration, gradation, the mixing amount of fly ash, permeability liquid and the interaction between leachate and loess et al.The experiment results from the determination of the major pollutant in leachate such as COD,NH₃-N show that the soil samples have certain removal effect on COD and NH₃-N.