Experimental investigation of Strength and Microstructural behavior variations of oil contaminated clay (Area: Masjedsoleyman)

Global oil production exceeds two million tons per year, contaminating the soil around oil facilities. Consequently, the soil’s geotechnical properties are modified. Since Iran is an oil-rich country with numerous refineries and oil extraction facilities, it is crucial to study the mechanical behavior of contaminated clay soils. This study examines the stabilization of oil-contaminated clay (CH) soils in the Masjedsoleyman contaminated clay soils by adding lime. To this end, laboratory tests were conducted to determine the chemical properties, Atterberg limits, standard compaction, and unconfined compressive strength (UCS) of the soil and conduct a microstructural analysis. As a result, 144 contaminated soil samples (76 mm in height and 38 mm in diameter) containing 0, 4, 7, and 10% oil were synthesized by adding 0, 3, 6, and 9% lime. The samples were subjected to unconfined strength tests and microstructural analyses after 1, 14, and 28 curing days. The results of the standard compaction test revealed that the optimum moisture content (OMC) of samples with greater oil contamination decreased by 44.4%, while their maximum dry density (MDD) increased. The unconfined compressive tests indicated that adding 6% lime resulted in the highest unconfined strength (416.6%) compared to other cases. As curing time increased for lime-stabilized samples, the unconfined compressive strength of the samples improved due to the cementation of lime particles with clay soil. The microstructural analysis results demonstrated that the 7% oil-contaminated clay soil had a laminar and discontinuous structure and numerous porous spaces between soil particles. However, longer curing times reduced the porosity and cavities in samples stabilized with different lime percentages. This confirmed the high cation exchange capacity of lime and the presence of pozzolanic reactions, which increased the unconfined compressive strength of the samples. Overall, this study demonstrates the efficacy of adding lime in stabilizing the contaminated clay and the potential use of stabilized contaminated clay as an alternative construction material and practice in the environmental protection of sites.