Saudi Cultural Missions Theses & Dissertations
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Item Restricted Investigating the Mechanical Characteristics of Clay Contaminated with Engine Oil(University of Technology Sydney, 2024-08-25) Omar, Khalid; Fatahi, BehzadGeotechnical engineers face the challenge of enhancing soil properties impacted by oil contamination, which disrupts the soil's natural composition and negatively affects its physical and mechanical characteristics. Oil-contaminated soils pose environmental hazards to ecosystems, necessitating innovative and environmentally friendly remediation strategies to eliminate hazardous pollutants and facilitate site redevelopment. This study investigates the effects of oil contamination on the mechanical properties of soft clay and its treatment using cement. The influence of pre-contamination moisture content (PMC) on soil contaminated with used engine oil was examined. The mechanical properties of oil-contaminated soil treated with various cement contents (0%, 5%, 10%, and 20%) were investigated. Additionally, the behaviour of low-plasticity clay contaminated with fresh engine oil was studied to understand oil contamination's effects on soil plasticity. An extensive experimental program was implemented, including SEM microstructural analysis, Atterberg limits and linear shrinkage tests, unconfined compressive strength (UCS) testing, bender element analysis, direct shear testing, and amplitude sweep tests. Tests were performed on high and low-plasticity clay mixed with various oil concentrations (0% to 16%), including fresh and used engine oil. Results showed that adding used engine oil with different PMC negatively affected high-plasticity soil, reducing UCS by 64% when oil content increased from 0% to 6%. Linear shrinkage and plastic limit increased while the liquid limit decreased. Similar observations were made in low-plasticity soil contaminated with fresh engine oil, where increasing oil contents increased Atterberg limits. Mechanical properties, including shear strength and shear modulus, decreased with increased contamination contents for both low and high-plasticity soil contaminated with used and fresh engine oil. Cement addition substantially improved the mechanical properties of high-plasticity clay contaminated with oil. Cement significantly increased the liquid limit and linear shrinkage value at various oil contents, enhancing the soil's shear strength, shear modulus, friction angle, and cohesion. Laboratory results showed that treating oil-contaminated soil with cement improves its mechanical properties. Cement hydration creates a gel-like coating that binds particles and reduces permeability, forming a strong matrix that encapsulates oil droplets and slows their mobility. This treatment changes pollutant acidity, pH, and solubility through pozzolanic reactions, improving the mechanical properties of contaminated soil. This thesis thoroughly examines the effects of used and fresh engine oil contamination on soil, focusing on its impact on low and high-plasticity soils. The study also investigates the influence of cement treatment on the mechanical properties of expansive soil contaminated with used engine oil, finding cement stabilization to be a viable remedy for building and roadway infrastructure construction.16 0