Abstract
Construction of a waste disposal site requires an effective barrierthat separates waste from a sub-base and minimizes the migrationof contaminants from the site to an aquifer. Barrier layers mostoften used are natural clayey deposits or compacted clay liners andPEHD geomembranes. However, some regions, the Croatian karstfor example, are mostly short of clay. For this reason, the use ofpulverized stone, the by-product in the building-stone industry – as apotential liner material was investigated. Considering diffusion is animportant mechanism of contaminant transport through barriers, thispaper describes the method and apparatus for determining the diffusioncoefficient of pulverized stone. Measured diffusion values wererelated to sample compaction and compared with the physical propertiesof clay, geosynthetic clay liners and PEHD geomembranes. Otherphysical properties of pulverized stone such as the filtration coefficient,density and particle size distribution are also presented. Finally,the suitability of pulverized stone for barrier construction is discussedbased on the results obtained.
Highlights
Construction of a waste disposal site necessarily involves implementing an effective barrier which is intended to isolate waste from the sub-base and minimize the transport of contaminants from the site to an aquifer
Considering diffusion is an important mechanism of contaminant transport through barriers, this paper describes the method and apparatus for determining the diffusion coefficient of pulverized stone
As the measuring technique was found to be suitable for this research, the diffusion coefficient tests were carried out for the samples of clay from the Novačica site, pulverized stone, TRISOPLAST® and the geosynthetic clay liner (GCL)
Summary
Construction of a waste disposal site necessarily involves implementing an effective barrier which is intended to isolate waste from the sub-base and minimize the transport of contaminants from the site to an aquifer. Natural clayey deposits and compacted clay liners with PEHD geomembranes are the barrier liners that are generally used. In some regions, the Croatian karst for example, clay is not available in sufficient quantities and, other natural materials should be considered. The properties of pulverized stone were compared to those of the Novačica clay (the clay which was used for the barrier liner applied in the Jakuševec landfill) and of a geosynthetic clay liner (GCL), the material which is usually used in “clayless” regions. The transport of contaminants through porous media such as clay, pulverised stone and a GCL, which are used as barriers, may be the result of only two physical processes, namely convection and molecular diffusion. Since migration of chemical substances through barriers caused by convection is negligible, diffusion is a dominant mechanism of contaminant transport. The transport (caused by diffusion) of an observed tracer in a solution can be described by Fick’s first law (DAGAN, 1989):
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