Discussion on permeability characteristics of lime and fly ash solidified oil-contaminated soil and its engineering reuse

The permeability of treated contaminated soil is an important factor to consider when reusing polluted soil in engineering projects. In this study, lime and fly ash were chosen as solidification materials due to their ability to both adsorb and solidify contaminants. The permeability coefficients of petroleum-contaminated soil before and after solidification, as well as the residual petroleum content within the soil, was investigated under varying parameters such as confining pressure, osmotic pressure and contamination intensity. X-ray diffraction and scanning electron microscopy were used to analyze the evolution of permeability and the migration and diffusion patterns of pollutants, providing insights into the engineering reutilization potential of solidified petroleum-contaminated soil. The results showed that the adsorption effect of the solidified product on petroleum molecules weakened the hydrophobicity of the petroleum, increasing the effective permeation pathways in the soil. The permeability coefficient of solidified petroleum-contaminated soil was two orders of magnitude higher compared to non-solidified soil. Both solidified and non-solidified petroleum-contaminated soil exhibited decreased permeability due to the enhanced adsorption and interception capacity of the soil matrix for petroleum, as well as the elevated confining pressure, osmotic pressure, and contamination level, which intensified the interception among soil particles. The solidification process effectively controlled the migration and diffusion of petroleum contaminants under permeation conditions. The residual petroleum content in various locations closely approximated the initial content, reducing the risk of pollution through permeation, Considering the mechanical properties (compressive strength of 1 280.1 kPa, shear strength of 388.88 kPa), permeability (ranging from 4.28×10-6 cm/s to 7.39×10-6 cm/s), and migration control characteristics (fluctuation rate from 0.3% to 4.9%) of lime and fly ash, it can be concluded that lime and fly ash solidified petroleum-contaminated soil can be reused in the construction of subgrade materials that require impermeability. © 2024 Biodiversity Research Center Academia Sinica. All rights reserved.