Effects of diesel contamination on clayey sand properties

This study examines how diesel contamination affects the compaction and shear strength of clayey sand, filling a gap in understanding the long-term impact of hydrocarbons on soil. It uniquely assesses diesel-soil interactions using a modified drying protocol (vacuum drying at 40 °C) to minimize diesel evaporation. Soil samples were prepared with 0%, 5%, and 10% diesel contamination by dry weight and compacted to densities of 1.5 g/cm³ and 1.8 g/cm³ at 15% water content. Compaction, Atterberg limits, and direct shear tests were performed, and Scanning Electron Microscopy (SEM) was used to analyze microstructural changes. Results show that 5% diesel contamination initially enhances particle arrangement, increasing maximum dry density from 1.72 g/cm³ to 1.82 g/cm³ in pure sand and plasticity index by 12%. However, 10% contamination weakens soil structure, reducing dry density by 8% in bentonite-rich mixtures, cohesion by 39% (from 18 kPa to 11 kPa), and the internal friction angle from 36° to 29°. SEM images confirm these findings, revealing particle coating and increased pore space (up to 15% void ratio rise), indicating reduced interparticle bonding. Effects stabilize after ~ 10 days due to volatile component dissipation. Denser soils (1.8 g/cm³) were more resistant to contamination than less dense soils (1.5 g/cm³), with bentonite-rich soils (45%) showing 25% greater shear strength retention, suggesting a remediation approach. These results highlight the mechanical deterioration and microstructural changes in diesel-contaminated soils, emphasizing the need for specific geotechnical evaluations in hydrocarbon-affected regions.