Study On Geoenvironmental Characteristics Of Clay And The Behavior Of Clay Liner In MSW Landfills

With the quantity of municipal solid waste increasing day-by-day, sanitary landfills for these waste are more and more in China. But there are still many problems of landfills in practice, e.g. the isolation and safe-contaminant systems of landfill. On the basis of the theory of contaminant migration in clay, the geoenvironmental characteristics of clay and their effects on the effectiveness of clay liners in landfill are studied in this thesis.Clay has become one of the most important barrier materials in landfill, because of their low hydraulic conductivity, high adsorption capacity against chemicals and retardation of chemicals transport. Some investigations on cation adsorption of clay have been carried out, via laboratory batch tests for the assessment of adsorption parameters. Then a new adsorption isotherm for these cations is presented, in order to consider the maximum adsorption capacity of clay. After the batch tests, geotechnical characteristics of cation contaminated clay are studied. It is found that adsorbed cation can induce Significant changes in the mechanical properties of clay.: To determine diffusion parameters of cations through clay, some laboratory tests are carried,out via horizontal and vertical diffusion tests. The results show that some factors, such as cation concentration, accompanying cation, flow rate, have significant effects on the diffusion of cation through clay.On the basis of the aforementioned tests, influences of the geoenvironmental characteristics of clay on the effectiveness of clay liners are analyzed in this thesis. The analysis results show that the technical code for sanitary landfill in China would satisfy the antipollution request of surrounding site and groundwater, on condition that the water level in landfills is limited to a small value. Meanwhile, the adsorption and diffusion characteristics of clay affect the contaminant transportation in clay liners obviously. Thus the effectiveness of clay liners can be improved by means of increasing adsorption capacity of clay or decreasing diffusion property through clay. Moreover, the recirculation of leachate in landfills is also studied to evaluate the potential influence on the effectiveness of clay liners. The results show that thequantity of recirculation leachate should be controlled to meet the demand of water level in landfills when the drainage system works well. And leachate recirculation can improve the decomposition rate of solid waste and shorten the stabilization time of landfill.