Experimental study on the movement of oil spill under freeze-thaw action

Oil leakages cause environmental pollution, economic losses, and even engineering safety accidents. In cold regions, researchers urgently investigate the movement of oil spill in soils exposed to freeze-thaw cycles. In this study, a series of laboratory model experiments were carried out on the migration of oil leakage under freeze-thaw action, and the distributions of the soil temperature, unfrozen water content, and displacement were analyzed. The results showed that under freeze-thaw action, liquid water in soils migrated to the freezing front and accumulated. After the pipe cracked, oil pollutants first gathered at one side of the leak hole, and then moved around. The pipe wall temperature affected the soil temperature field, and the thermal influence range below and transverse the pipe wall (35-40 cm) was larger than that above the pipe wall (8 cm) owing to the soil surface temperature. The leaked oil's temperature would make the temperature of the surrounding soil rise. Oil would inhibit the cooling of the soils. Besides, oil migration was significantly affected by the gravity and water flow patterns. The freeze-thaw action would affect the migration of the oil, which was mainly manifested as inhibiting the diffusion and movement of oil when soils were frozen. Unfrozen water transport caused by freeze-thaw cycles would also inhibit oil migration. The research results would provide a scientific reference for understanding the relationship between the movement of oil pollutants, water, and soil temperature, and for establishing a waterheat-mass transport model in frozen soils.