Geotechnical issues on waste disposal and waste landfill design

从岩土工程的角度对垃圾处理场进行基于性能的结构设计，对于有效缓解渗滤液渗漏对地面和地下水的污染是必不可少的。本研究从降低环境风险的角度考察了粘土和废弃物在填埋场复盖和底衬系统中的适用性。本研究取得的主要成果如下：(1)通过渗透试验、保水试验等一系列室内试验，评价了废渣对填土覆盖层的适用性。在此基础上，从水量平衡的角度探讨了填埋场覆盖的有效性。(2)由于填埋场的入渗量显著减少，因此设置填埋场可以促进废弃层的厌氧条件。通过实验室间歇浸出和柱浸试验，考察了厌氧条件下无机污染物的浸出行为。结果表明，在低ORP条件下，即使在酸性条件下，重金属的浸出也会减少。因此，通过设置填土覆盖系统，可以最大限度地减少垃圾中重金属的淋失。(3)对土工合成粘土衬里和渗透了无机溶液的膨润土的化学相容性进行了评价，探讨了它们作为填埋底衬材料的适用性。在考虑预水化效应和无机溶液中阳离子浓度的情况下，研究了无机溶液对其导水性和膨胀性的影响。(4)提出了垃圾填埋场衬层(土工膜、粘土衬层、钢板桩)性能的评价方法，重点研究了双层衬层体系的有效性。在参数研究的基础上，提出了适合内陆和近海填埋场的衬砌结构。

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.