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垃圾填埋场中渗滤液运移数值分析

Numerical Analysis for Leachate Migration in Muncipal Solid Waste Landfill

【作者】 岳强

【导师】 张金利;

【作者基本信息】 大连理工大学 , 岩土工程, 2010, 硕士

【摘要】 现代卫生填埋场受降雨入渗与垃圾含水量影响,可产生一定量的渗滤液,为防止渗滤液在填埋场内大量积存,需要依据填埋场规模、气象条件等预估渗滤液产量,设计相应的导排系统将其导入渗滤液收集池或污水处理厂进行处理。因此,对特定导排系统,分析与研究渗滤液随时间变化规律,对于评估渗滤液导排系统有效性与可靠性具有重要的理论价值与广阔工程应用前景。在考虑降雨条件下,本文依据渗流理论,建立了垃圾土的渗流方程,采用数值方法计算与分析垃圾土中的非稳态渗流场变化过程,主要开展以下研究工作。1基于质量守恒与Darcy定律,建立了垃圾土中的饱和-非饱和渗流计算模型。依据文献资料,采用Brooks-Corey模型,通过参数拟合,分别给出处于填埋场不同层中垃圾土的土-水特征曲线与非饱和渗透系数曲线。2依据所建立的一维非饱和渗流计算模型,在考虑降雨入渗与自由排水边界条件下,计算与分析填埋场中不同深度处垃圾土的饱和度随时间变化过程。通过变动初始吸力分布与降雨强度参数,探讨与分析非饱和渗流过程的影响因素。之后又建立了渗透具有各向异性的垃圾土降雨入渗的计算模型,模拟计算了一定时间内的降雨入渗,分析了水分运动的特性。3针对垃圾填埋场分层填筑的实际情况,建立了包含有三层垃圾土、两层覆盖层、底部排水系统的二维的渗流计算模型。在计算模型中分别考虑垃圾土的各向异性与降雨条件。在一定降雨条件下,采用数值方法,计算与分析了垃圾堆体中渗流场随时间变化规律;垃圾土与覆盖层中的孔压随时间变化特性;浸润线的变化发展过程;对比分析了垃圾土的各向同性和各向异性对垃圾堆体渗流场的影响。

【Abstract】 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.

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