竖井抽水下垃圾填埋场渗滤液运移规律研究

Investigation into leachate transport in MSW landfills under pumping of vertical wells

城市固废由于组成成分的多样性及分层填埋等原因,导致渗滤液运移存在明显的优先流及各向异性现象。在成都某填埋场开展多口竖井抽水及水位恢复试验,同时结合高密度电法技术（ERT）现场大尺度研究渗滤液分布及运移规律。多口竖井水位恢复试验显示填埋体内渗滤液运移具有明显的不均质性,表现为同一填埋场不同位置的竖井抽排性能差异较大,竖井周围垃圾渗透系数值分布范围为2.35×10-5-3.90×10-4 cm/s。竖井抽水下周围监测井的水位异常变化表明渗滤液补给存在明显优先流特征。ERT监测渗滤液抽水及回灌过程中堆体内电阻率变化,进一步揭示了现场渗流存在显著的各向异性和优先流特征,主要渗流路径与水平向呈0-30°。

Owing to the composition diversity of MSW and the compacted nature in landfills, the leachate transport in landfills is found to be dominated by the preferential flow and shows significant anisotropy（i.e., horizontal permeability higher than vertical one）. The vertical well pumping and leachate level recovery tests are conducted at Chengdu landfill. Meanwhile, the leachate distribution and transportation characteristics are examined quantitatively and qualitatively using electrical resistivity tomography（ERT）. Through the vertical well pumping and leachate level recovery tests, it is found that the leachate transport in landfills is highly heterogeneous. The performance of vertical wells at different regions of this landfill shows great difference, and the hydraulic conductivity of the surrounding waste ranges from 2.35×10-5 to 3.90×10-4 cm/s. The leachate levels in the surrounding monitoring wells change unusually under pumping of vertical wells. It is mainly due to the existence of preferential flow in the leachate transportation process. In addition, the monitoring results on changes of waste resistivity in the process of leachate pumping and recirculation by ERT further reveal that there are significant anisotropy and preferential flow characteristics in leachate transportation. And the angle between leachate seepage path and horizontal direction is found to be 0-30°.