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<p>Hydrocarbon contamination significantly influences the dynamic behavior of calcareous sands, yet quantitative data remain scarce. In this study, 42 resonant column and cyclic triaxial tests were conducted on Heleylah calcareous sand under confining pressures of 75, 150, and 300&#xa0;kPa, with contamination levels of 0, 4, 8, and 12% using light crude oil and gas oil. Crude oil contamination consistently increased the small-strain shear modulus (G) and reduced the damping ratio, whereas gas oil produced the opposite effect. Increasing the confining pressure from 75 to 300&#xa0;kPa elevated G by 69.5% in clean sand, by 52–61% in crude-oil-contaminated sand, and by 80–101% in gas-oil-contaminated sand. The influence of crude oil was most pronounced at 4%, where stiffness improvement was maximized; higher contamination levels produced only marginal additional changes. At 75&#xa0;kPa, the linear threshold strain rose from 0.00135% in clean sand to 0.00155% with 4% crude oil and 0.00172% with 4% gas oil. Microstructural analyses confirmed that these trends arise from both the viscous and adhesive nature of crude oil, which generates artificial cohesion, and the formation of oil–mineral aggregates that reinforce interparticle bonding, whereas gas oil primarily acts as a lubricant. A modified hyperbolic model, expressed as a function of confining pressure and contaminant percentage, reproduced the measured modulus-reduction curves with R² &gt;0.999 and RMSE &lt; 0.0005. Overall, the findings establish a predictive framework that enhances the reliability of geotechnical design for infrastructures located in hydrocarbon-polluted coastal zones.</p>

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Strain-Dependent Dynamic Behavior of Hydrocarbon-Contaminated Heleylah Calcareous Sand

  • 期刊论文

  • 发表日期：

    2026年1月9日

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  • Mahdi Yoosefi Taleghani,
  • Alireza Saeedi Azizkandi,
  • Mehran Karimpour-Fard,
  • Kamyar Bakhshi

摘要

Hydrocarbon contamination significantly influences the dynamic behavior of calcareous sands, yet quantitative data remain scarce. In this study, 42 resonant column and cyclic triaxial tests were conducted on Heleylah calcareous sand under confining pressures of 75, 150, and 300 kPa, with contamination levels of 0, 4, 8, and 12% using light crude oil and gas oil. Crude oil contamination consistently increased the small-strain shear modulus (G) and reduced the damping ratio, whereas gas oil produced the opposite effect. Increasing the confining pressure from 75 to 300 kPa elevated G by 69.5% in clean sand, by 52–61% in crude-oil-contaminated sand, and by 80–101% in gas-oil-contaminated sand. The influence of crude oil was most pronounced at 4%, where stiffness improvement was maximized; higher contamination levels produced only marginal additional changes. At 75 kPa, the linear threshold strain rose from 0.00135% in clean sand to 0.00155% with 4% crude oil and 0.00172% with 4% gas oil. Microstructural analyses confirmed that these trends arise from both the viscous and adhesive nature of crude oil, which generates artificial cohesion, and the formation of oil–mineral aggregates that reinforce interparticle bonding, whereas gas oil primarily acts as a lubricant. A modified hyperbolic model, expressed as a function of confining pressure and contaminant percentage, reproduced the measured modulus-reduction curves with R² >0.999 and RMSE < 0.0005. Overall, the findings establish a predictive framework that enhances the reliability of geotechnical design for infrastructures located in hydrocarbon-polluted coastal zones.