Hydraulic Performance Study For Cracking Compacted Clay Liner In Landfill

Landfill method is the most important method for municipal solid waste (MSW)disposal all around the world. This method can treat a large mount of waste and thetreatment technology is relatively simple. But it also has some environmental problems,such as leakage of landfill gas and leachate in the process of landfill. If not properlyhandled, these secondary pollutions will be harmful for the nearby public health. Howto take effective measures to prevent secondary pollution is an important issue wecurrently face.The liner system is an important part of the landfill. However, it can easily crackunder the influence of the external environment change. Cracks have importantinfluence on the hydraulic performance of liner system. So we must study the crackssystematically to make sure the reliability and validity of liner system. Using laboratoryexperiments, theoretical analysis and other methods, the article analyzed the cracksdevelopment law in the condition of dry-wet cycle, the hydraulic performance of linersystem under the effect of dry-wet cycle analog leachate. The main research contentsare as follows:(1)Laboratory test was conducted to study on the evolution law of the cracks of clayunder dry-wet cycles. The geometry elements of cracks were extracted with rasterimage vectorization technology. The action mechanism of cracks development and thevariation law of cracks were investigated from de-wet and dry-wet cycle processes.(2)In order to investigate the mechanism between leachate and soil preliminarily, theconsistency limits of different kinds of soil-bentonite mixture under solution wasdiscussed.(3)Laboratory test was conducted to study on the cracks effect on the hydraulicperformance of liner system. The hydraulic conductivity of cracks clay and no-crackclay was tested, with degassing water and several solutions as permeated liquids. Therelationship between hydraulic conductivity and consistency limits was discussed.(4)Pollution transport was calculated with the liner divided into crack part andnon-crack part. Using convection-dispersion equation, the effect of the extending depthof cracks, the thickness of liner and the hydraulic conductivity of two parts on linerperformance was discussed.