Evaluation of clay soils’ permeability: A comparative study between the natural, compacted, and consolidated clay soils

Abstract

Many cities in Turkey use groundwater in order to meet their need of drinking water. Municipal solid waste landills in all of the cities are major threat for groundwater. Low permeability clay soils by landill operators are used as a standard practice. However, it has been shown that certain contaminants change the structure of clay soils, making them highly permeable. A lot of investigators have demonstrated that concentrated organic chemicals can alter compacted clays and cause increase in permeability. In this study, the effects of leachates on permeability and the treatment capabilities of the natural, compacted-consolidated, and compacted clay soil have been investigated. Clay soil samples were obtained from the Sile-Komurcuoda landill area on the Asian side of Istanbul. In the experimental studies, Standard Proctor compaction tests and consolidation tests were applied to the clay soil obtained from the same area. The clay soil samples have permeability k of between 1.10 -7 and 1.10 -9 m/s. In order to determine the removal rate of the natural, compacted-consolidated, and compacted clay soil, Pb, Cr, Mn, and Fe are measured in the inluent and efluent of the lab-scale reactor. The effects of leachates on the permeability of the natural, compacted-consolidated, and compacted clay soil samples have been analyzed. Initially, some decrease has been observed in the clay soil permeability associated with the contamination. The suspended solid matters in the leachates have illed the spaces between the particles of the clay soil pores and this caused a decrease in the permeability. After some time, it is shown that leachates may cause increase in the permeability. The treatment capabilities of the natural, compacted-consolidated, and compacted clay soil samples were quite high. The highest removal rates and the lowest permeability are obtained in natural clay, compacted-consolidated clay, and compacted clay, respectively.