Numerical Analysis For Leachate Migration In Muncipal Solid Waste Landfill

Modern sanitary landfill waste will produce a certain amount of leachate because of the rainfall infiltration and the changing of the water content in the waste soil. In order to prevent the accumulation of leachate in the landfill, the drainage systems should be design based on the landfill size, weather conditions and other effects expecting the production of leachate. So, for the specific drainage system, analysis and studying on the change of the leacheate in the landfill is very important theoretical value and broad application prospect to assess the effectiveness and reliability.Based on unsaturated-saturated seepage analyses theory, the seepage model of the waste soil was established under the condition of rainfall. The method of finite element simulated and analysis the process of the changes of seepage field in the waste soil. The main contents and conclusions are as follows.1,Based on the mass conservation and Darcy's law, the saturated-unsaturated flow model was established. And three boundary conditions are introduced. The soil-water characteristic curves and the hydraulic conductivity function of the three kinds of waste soil are fitted according to Brook-Corey model.2,According to the calculation model of the one-dimensional seepage flow, the process of the rain infiltration in kinds of waste soils was simulated, which showed the changes of distribution of pore water pressure in the solid waste. By changing the initial conditions and the intensity of rainfall conditions, the factors of affecting water movement in the waste soil were discussed. Then unsaturated seepage analyses were carried out to investigate the movement of water in the anisotropic waste soil.3,According to the actual situation of the landfill established the model of two-dimensional seepage flow, which consists of three floors of waste soils, two floors of interim soil covers and the drainage system at the bottom. The saturated-unsaturated analyses were carried out to investigate the movement of water in the isotropic landfill and the anisotropic landfill. The obtained results show that the por water pressure of the soils and covers in the isotropic landfill and the anisotropic landfill changes. And the process of the phreatic line at the bottom of the landfill and the wate head at the covers in the landfill change and development process was shown in the isotropic landfill and the anisotropic landfill. These derived the difference of the water movement in the isotropic landfill and the anisotropic landfill.