The Effect of Aging on Hydrocarbon-Contaminated Soils with Different Clay Content

Hydrocarbon contamination is regarded as one of the most crucial soil pollution incidents, altering the geological features of soils. Oil is a complex mixture of hydrocarbons, which gradually penetrates through the soil and spreads. Oil derivatives undergo physical and chemical changes in soil due to evaporation, absorption, and biodegradation by soil microorganisms, making this type of pollution one of the challenging topics in geotechnical engineering. While several studies have investigated the effect of various amounts of oil and its derivatives on the geotechnical properties of different soils, only a few studies have focused on the impact of hydrocarbon aging. On the other hand, the effect of clay content on aging of hydrocarbon-contaminated soils has not been fully studied before. To fill this gap and evaluate the importance of contaminated soil aging, compaction, triaxial test, unconfined compression strength, Water Holding Capacity, pH, and Scanning Electron Microscopy experiments are performed in this study on sand-kaolinite mixtures containing different clay to sand ratios, and contaminated with 6% used motor oil by dry weight of the soil. The experiments were carried out instantly, 1 week, 1 month, 2 months, 6 months, 12 months, and 24 months after contamination. The results indicate that the compaction parameters change significantly for the soil with a high percentage of clay (50% clay), over the course of time. Moreover, cohesion and internal friction angle increase and compression strength changes due to the stiffening and variations of used motor oil. Aging is observed to be highly dependent on clay content.