Time-Dependent Behavior of Crude Oil-Contaminated Sands Under Static and Dynamic States

In the aging of oil-contaminated soils, the ambient conditions that the soils are naturally exposed to can affect soil properties over time while most studies stored the prepared samples in the laboratory with well-controlled environments. The tests on samples kept in the laboratory cannot thus reflect the actual behavior. This study compares the time-dependent characteristics of static and dynamic parameters of crude oil-contaminated sands stored in the laboratory and left in natural conditions using cyclic simple shear tests. Crude oil-contaminated samples prepared from sands with various gradations with 6% crude oil contamination were held in natural and laboratory environments for up to 24 months and tested at 3-month intervals under a constant void ratio and relative density of 60% to highlight the impacts of stored conditions of the samples in conjunction with the aging on shear modulus, damping ratio, and friction angle of sands. With the long investigation period in the study, the fluctuation of properties during the first year due to seasonal change can be seen. The testing results indicate that the impact of contaminants in the sands reduces with the aging effect. Both aging and stored conditions had the greatest effect on the static and dynamic parameters of coarse sand. While the smallest effect is seen for dynamic parameters of fine sand. The study provides useful information and necessary considerations for using oil-contaminated soils safely.