Abstract: In this study, the nano-SiO2 (NS)and lime were used to solidify the coastal petroleum-contaminated soil. The effects of nano-SiO2 and lime on the solidification of coastal petroleum-contaminated soil(PCS) were studied through Atterberg limits tests, unconfined compressive strength tests and pH tests. The microstructure and mineral composition of typical modified petroleum-contaminated soil were analyzed by scanning electron microscopy and X-ray diffraction tests. The results indicate that the unconfined compressive strength of petroleum-contaminated soil with 5% petroleum content modified by NS-lime increases significantly. By adding 1% or 2% NS to the 3% lime-modified petroleum-contaminated soil, the 7-day saturated unconfined compressive strength of lime-modified petroleum-contaminated soil reaches 421 kPa and 727 kPa, respectively, more than 3 times and 5 times of that without NS. Meanwhile, adding NS reduces the pH of lime-modified petroleum-contaminated soil and the harm of lime to the environment. Furthermore, the scanning electron microscope test and X-ray diffraction test also prove that, compared with adding lime alone, when NS and lime are combined, the NS accelerates the hydration reaction of lime, promotes the formation of hydrated calcium silicate, and greatly improves the strength of coastal petroleum-contaminated soil.

Key words: NS-lime, petroleum-contaminated soil(PCS), unconfined compressive strength, microstructure