Geotechnical issues on waste disposal and waste landfill design

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Performance-based structural design for waste disposal site from the geotechnical viewpoint is essential for the effective mitigation of ground and groundwater contamination due to the leachate leakage. This study examines the applicabilities of clay and waste materials to the land fill cover and bottom liner system in aspects of environmental risk reduction. The main results obtained in this study can be summarized as follows :(1) The applicability of waste sludges to land fill cover layer was evaluated through a series of laboratory experiments such as hydraulic conductivity tests and water retention tests. Based on these experimental results, the effectiveness of land fill cover was discussed from the viewpoint of water balance.(2) The installation of land fill cover could promote the anaerobic condition in waste layer because the infiltration amount is significantly reduced. Leaching behavior of inorganic contaminants under anaerobic condition was examined through the laboratory batch and column leaching tests. It can be concluded that the leaching of heavy metal is reduced under the condition of low ORP even in acidic condition. Hence, the leaching of heavy metal from waste can be minimized by the installation of land fill cover system.(3) The chemical compatibilities of geosynthetic clay liners and bentonite permeated with inorganic solutions are evaluated to discuss their applicabilities as land fill bottom liner materials. The influence of inorganic solutions on their hydraulic conductivities and swelling behaviors are investigated considering the prehydration effect and the concentrations of cations in inorganic solutions.(4) The methods for evaluating the performance of landfill liners (geomembrane, clay liner, steel sheet pile) are proposed with the focus on the effectiveness of the double liner system. An appropriate liner structure of the inland and offshore land fill sites is proposed based on the parametric studies using the proposed methods.