EFFECT OF WETTING AND DRYING CYCLES ON THE COMPRESSIVE STRENGTH OF OIL-CONTAMINATED SOIL TREATED WITH LIME AND FLY ASH

In the northern coastal area of China, the alternated phenomenon of rainy season and dry-windy weather is threatening the soil stability. It needs to improve the mechanical properties of treated soil under dry and wet cycles before utilization. The mechanical distribution of oil contaminated soil treated with lime and fly ash are studied in this manuscript. Unconfined compressive strength index is chosen. Wet and dry cycle process is simulated. Results indicate the follows. (1)The quality of treated oil contaminated soil decreased with wet-dry cycle process. It presented small fluctuations in 6 times, then decreased significantly during 7-8 times, and stabilized finally after 9 times. The maximum decrease is 4.5%. (2)The compressive strength of oil contaminated soil treated with lime and fly ash increased first and then decreased with the increasing of dry and wet cycles. It reached the maximum at 3 times. It stabilized after 7 times. The residual strength was more than 70% of initial strength. So the oil contaminated soil treated with lime and fly ash had good water stability. (3)The water stability of treated oil contaminated soil reduced with the increasing of oil contamination levels. The failure gradually tended to hardening type with wet-dry cycle. The best proportion of lime and fly-ash was 0.75. Therefore, the oil-contaminated soil can be used as roadbed fill to achieve the purpose of recycling contaminated soil.