Effect of residues from a burnt oil refinery on the compaction parameters and strength of clayey sand

Soil contamination by petroleum contaminants and their derivatives has harmful effects on the environment, including groundwater and marine contamination and on the geotechnical properties of the soil. It decreases the soil strength, bearing capacity of foundations, and slope and trench stability. Petroleum contaminants can also alter the structure of cohesive granular soil. The present study examined the effect of acidic sludge and dirt filter contaminants from a burnt oil refinery on the compaction parameters and strength of clayey sand. Proctor compaction and direct shear tests were performed on soil samples containing 0%, 3%, 6%, and 9% of these pollutants. Direct shear tests were performed at different depths and stresses on soil samples from sandy soil contaminated with the residue from a burnt oil refinery. The results showed that with approximately 4 to 5% increase in pollution, the maximum dry soil unit weight increases and decreases with the addition of more contaminants. Also, the friction and dilatancy angles of the soil decreased. The sample containing 9% pollutants recorded the most significant decrease in these values. The effect of surface-active agents on acidic sludge caused an increase in the Van der Waals force between the particles, resulting in an increase in soil cohesion. Contamination with 47.7% SiO₂ from the dirt filter increased the soil cohesion parameter. Under similar experimental and loading conditions, an increase in the acidic sludge and dirt filter contents decreased the soil shear strength and dilatancy angle.