Characterization and mechanism analysis of stabilized/solidified oil-contaminated soils

Effective remediation of oil-contaminated soil is an essential environmental issue, and various techniques have been proposed/developed for this purpose. One of the practical and cost-effective methods is solidification and stabilization (S/S). Accordingly, the influences of stabilizing agent (including cement, lime, and nano-silica) on the geotechnical and leaching behaviors of stabilized/solidified oil-contaminated soils were investigated through a comprehensive laboratory experiment. Regarding the unconfined compressive strength (UCS) of samples, the UCS value improves with increasing oil content up to 5% and then reduces with any increase in oil content in all samples. In addition, the maximum UCS (130kPa) belonged to the sample with 5% oil content, which was stabilized/solidified by 5% cement. The results of direct shear test demonstrated that the friction angle ad cohesion improve with increasing the contents of stabilizing agent in all samples. Moreover, the highest friction angle (39.5°) was observed for the sample treated with lime (5%) at the oil content of 5%. The results of leaching test revealed that at a given oil content, the higher the stabilizing binder content, results in more reduction in leaching of total petroleum hydrocarbons (TPH). Cement shows superior performance on reduction of TPH leachability compared to the other studied binders. Addition of 1, 3, and 5 % cement to contaminated soil (with oil content of 20%) caused reduction of TPH leachability by 10.3, 13.7, and 16.8%, respectively. Therefore, the cement addition to contaminated sample not only is able to enhance the geotechnical characteristics, but also improves the reduction of TPH leachability.