掩埋場覆蓋層透氣性研究

Abstract

臺灣地區每年所製造出的一般廢棄物與事業廢棄物總量達2300萬公噸，而以86年度而言，其中有74%以上的垃圾是以掩埋方式處理，而近年也因為垃圾處理引發了許多的問題，其中最顯而易見的就是民眾對垃圾處理設施新建或延長使用的抗拒，長久以來，掩埋場的設計與施工品管的審核與查驗制度均非常草率，絕大多數的掩埋場都未能完全依據現行法規設置，造成民眾對政府失去信心，顯現出近乎非理性的抗爭，當然如何建造一個「與世隔絕」的掩埋場，是一個土木工程師引以為傲的，因此最終覆蓋系統的阻隔層設計就扮演著相當關鍵的角色。 而掩埋場阻隔層材料包括天然的黏土、地工□土毯、以及地工止水膜等，但是過去的研究多著重於阻隔層阻水的能力，對於其氣體的阻隔功能，卻未多與著墨，尤其是在經過乾濕循環、冰凍解凍、甚至是差異沈陷後，所產生的裂縫將引起透氣性的大幅上升，而本研究將焦點放在覆蓋層中之阻隔層，並探討其乾縮行為對覆蓋層透氣性行為之影響。 實驗結果中發現，不論是夯實黏土或是地工□土毯，在乾燥環境之下，皆無法抵抗乾縮變形而產生裂縫，且50cm的覆土亦不足以保護其下的材料，因此建議在乾燥地區掩埋場覆蓋層阻隔層的設計應加上地工止水膜，當作阻隔氣體的材料，以避免掩埋場中所產生的氣體，溢散至大氣之中，造成對環境的危害。

The amount municipal solid waste and industrial waste has increased to 23 million tons per year in Taiwan. In 1997, 74% of the wastes were disposed in landfills. There have been numerous buproar of uproar of citizens against the building of new landfills or extension of the service of old landfills. Not enough attention has been paid on the design and construction of the landfills. Most of the landfills. Most of the landfills in Taiwan have not been built to meet the standards set by current regulations. As a result, the design and construction of a modern landfill is a very challenging task for civil engineers in Taiwan. In addition for hundreds of old landfills without appropriate bottom lining system, the role of the final cover system becomes especially critical. The hydraulic barrier material used in landfills includes natural clay, geosynthetic clay liner, and geomembrane. Most of the research have been fooused on the ability of these barrier materials to retard the migration of water. The migration of gas has not gather very much attention. However, Iiners such as compacted clay and geosynthetic clay liner tend to crack due to wet/dry cycles and freeze/thaw cycles. For compacted clay liner, there is additional concern on the tension cracks caused by differential settlement. The research focus on the effect of desiccation on the change of gas permeability of hydraulic barrier in cover system.