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- Composite liner system (2) (entfernen)
Composite liners (a geomembrane in intimate contact with a mineral liner) are frequently used to line landfills and contaminated sites. It is therefore very important to characterise the behaviour of these systems even under extreme conditions.
An investigation was undertaken to determine the influence of a mixture of concentrated organic contaminants on composite liner materials taken from test cells that had been dismantled after a 12-year permeation test.
The organic hydrocarbons had permeated the HDPE-geomembrane and had then migrated or had been adsorbed within the mineral liners, depending on their properties. The obtained concentration profiles of the contaminant mixture components indicate that the various mineral layer materials have selective retardation abilities which correspond to the different parameters of the organic compounds as well as of the mineral layer.
In addition, contaminant transport in the composite liners tested was modelled and the results of the model analysis compared with measurement data. An example (acetone) illustrates the calculated spatial and temporal contaminant concentration.
The composite liners investigated exhibit a very good sealing capacity against the concentrated organic contaminants used.
The fabric of mineral liner materials that had been exposed to organic compounds over a 12-year period was investigated as part of a wider research project. Macromorphological and micromorphological changes in the fabric were identified using computed tomography and polarisation microscopy.
Special care was taken to ensure artefact free sampling and sample preparation, in particular, the drying method used, has a substantial influence on the quality of the thin sections.
Fabric changes due to contaminant permeation over several years are, by and large, relatively small and their intensity is material specific. Silty clay CML1, in particular, contains a somewhat greater number of fissures and voids in comparison with the original material. The superposition of various processes in both test procedures and sample preparation may lead to fabric changes which can impede interpretation of the results.