Evaluation of Oil Contamination Effect on Permeability and Shear Strength of Sandy Soils

Oil contamination in soil affects the geotechnical properties of soil and may lead to hazards. In this research, the effect of oil contamination on shear strength and permeability of sandy soils has been studied. To perform geotechnical tests, four sandy soil samples including poorly graded sand, well graded sand, muddy sand and clayey sand have been produced, then standard proctor test, atterberg limit test, direct shear test and permeability test have been carried out on samples. Crude oil used as the oil contaminant has been taken from Tehran Refinery and has been added to specimens with weight ratio of 12, 8, 4 and 16 percent by dry weight of soil. Total of 60 sandy specimens have been produced with different crude oil percentage, and geotechnical tests have been carried out on each specimen. Results of direct shear tests have showed that friction angle in all of sandy specimens is reduced by increasing oil content. The results also showed that oil contamination in well graded sand, poorly graded sand and muddy sand creates an artificial cohesion and decreases cohesion of clayey sand. Effect of oil components’ evaporation on shear strength has been studied on %16 contaminated specimens and direct shear test results have been discussed. Permeability tests showed that by increasing the crude oil, permeability coefficient of clayey sand increases permanently, while permeability coefficient in poorly graded sand, well graded sand and muddy sand first increases and then begins to decrease.