Effects of salt and solidification treatment on the oil-contaminated soil: A case study in the coastal region of Tianjin, China

Presence of salt increases the system complexity of multi-phase oil-contaminated soil. The coastal area of Tianjin, China, is a representative zone full of oil-contaminated soil with salt. By considering initial water content, oil content and dry density, this paper focuses on soil-water reaction and mechanical strength to investigate effect of salt on oil-contaminated soil. Application prospect of solidified oil-contaminated saline soil is also analysed. Results indicate that there is a reverse moisture absorption competition between oil and salt, and the liquid limit and plasticity index of the oil-contaminated soil with salt are lower than those without salt. Salt increases the water repellency and leads to a higher water content of low-density soil in the desorption process. The soil-water characteristic curve of the oil-contaminated soil increases in a quadratic-parabola under the salt saturation and supersaturation. With salt, the curves of the maximum dry density and the optimal water content show poor symmetrical distributions. When the oil content is more than 8%, salt on the strength of oil-contaminated soil shows a significant effect. Based on solidification of lime and fly ash, the strength of oil-contaminated soil with salt increases by 17.9-5.7 times, which meets requirements for engineering applications (like subgrade filler). It is concluded that solidification is an effective treatment to clean contamination for oil-contaminated soil with salt.