Effect of oil-contamination and water saturation on the bearing capacity and shear strength parameters of silty sandy soil

Abstract

This study investigates the effect of oil contamination and water saturation on the geotechnical properties of silty sandy soil. The silty sandy soil (SM) in this study was obtained from Prachuap Khiri Khan Province, Thailand, and the contaminant product was 95 octane gasoline. The SM soils were prepared in a tank model under the conditions of dry soil, soil with a water level, gasoline-contaminated soil of 2%, and gasoline-contaminated soil of 4%. A laboratory experiment (direct shear test) and a field experiment (lightweight penetration test) were performed on SM soil for all conditions. The lightweight penetration test results indicate that the ultimate bearing capacity in the case of soil with water saturation decreases by 90% on average compared to the dry soil condition. The ultimate bearing capacity for the gasoline-contaminated SM soils of 2% and 4% decrease by 30% and 52%, respectively, on average compared to the dry soil condition. Moreover, the internal friction angle obtained from the direct shear test linearly decreases with the gasoline content and reduces by at least half in the case of water saturation. The cohesion of the oil-contaminated SM soils increases with increasing oil content as according to the second-order polynomial regression, and the dry soil and saturated soil have similar cohesions. These results reveal that the oil contamination and water saturation cause the loss of shear strength and reduce the ultimate bearing capacity of SM soil.