Stabilization of crude oil-contaminated Bushehr carbonate sand: physical and chemical study

Liquefaction, a vital issue in geotechnical engineering, is often due to cyclic stress leading to the effective stress in the soil mass reaching zero. This phenomenon depends on several aspects, including the soil type. Most previous research has focused on the liquefaction behavior of silicate sands, which significantly differ from carbonate sands in terms of static and dynamic resistance. Therefore, this study investigates the liquefaction behavior of clean Bushehr carbonate sand (CBCS), crude oil-contaminated Bushehr carbonate sand (COCBCS), and stabilized crude oil-contaminated Bushehr carbonate sand (SCOCBCS). The stabilization process uses three additives, i.e., Nano clay (NC), Portland cement (PC), and silicon dioxide (SD). The study finds that the addition of 4% NC has the highest impact on stabilizing the liquefaction of Bushehr carbonate sand, causing an 8.5-fold increase in the number of cycles required for liquefaction to occur compared to when the sand is contaminated with crude oil. Among the additives, 2% SD is the least effective, resulting in only a 2-fold increase in dynamic resistance. SEM and XRD results show that the structure and particle size of the sands do not change when mixed with different percentages of crude oil. The chemical analysis results indicate that PC (due to its chemical composition) can more effectively alter the characteristics of treated samples. However, due to higher surface area, NC stabilizes the liquefaction potential of oil-contaminated Bushehr carbonate sands more efficiently than other stabilizer agents.