Pre- and post-cyclic behaviour of an unsaturated clayey soil contaminated with crude oil

Besides adverse impacts on the environment, pollution with hydrocarbon compounds such as crude oil affects the geotechnical parameters like deformation modulus and shear strength. The present research involves evaluation of clayey soil properties changes in an unsaturated state due to application of cyclic loads before and after contamination with crude oil. A series of constant water content (CW) static and dynamic triaxial tests were conducted on samples that were compacted to the same dry density but different degrees of saturation and net confining pressures. The soil studied was provided from a place near an oil refinery located in Iran's capital city and was artificially polluted with 3%, 6% and 9% crude oil. Deformation modulus reduction due to cyclic loads application was considerably more than reduction of shear strength. Also, these parameters increased due to increasing net confining pressure and initial matric suction. Several chemical tests and techniques were employed to investigate the chemical variations in soil structure and the role of different chemical components of crude oil on quantitative variations of soil characteristics.