The Study of Uncertainty in the Effect of Oil Contamination on Geotechnical Behavior of Sandy Soil Beneath Oil Storage Tanks

A leakage from oil storage tanks result in pollution of a large amount of soil by gasoil. Physical and chemical reactions between soil and the contaminant lead to a change in the geotechnical soil behavior. If it yields a negative effect, the strength of the soil may decrease and the stability of the storage tanks may weaken and resulting in the seeping of a large amount of the contaminant in the soil and groundwater. In concern with lack of information about precise leakage of oil, the precise level of pollution and changes in geotechnical parameters couldn’t be accessible. So, the application of the certain analysis together with the probability analysis could be helpful. In this study, the direct shear test was conducted on silica sand samples contaminated with 2, 4, 6, 12 and 16% of gasoil and the stability probability analysis was evaluated by Monte Carlo method. The results showed that increasing the contaminant fraction led to reduction of internal friction angle and bearing capacity of the soil. This trend was observed with a slight reduction up to 6% and then with a sharper decline. In addition, two probability criteria of reliability and rapture probability (RP) were studied by Monte Carlo and then compared with factor of safety (FS).