Effect of diesel-contamination on geotechnical properties of illite soil

Oil products contaminate the soil in a variety of ways. In addition to environmental hazards, petroleum pollutants change the geotechnical characteristics of the soils. Clayey soils have complicated behavior in the presence of organic liquids. To better understand the behavior of oil-contaminated clayey soils, an experimental laboratory investigation was performed on illite clay soil which was polluted by different amounts of diesel (0 to 20% by soil dry weight). In this paper, geotechnical properties of clean and contaminated illite specimens consist of compaction characteristics, compressibility, shear strength parameters and unconfined compression strength were evaluated through compaction, consolidation, direct shear and unconfined compression tests respectively. Additionally, the effect of diesel on the microscopic properties of the illite was studied by scanning electron and atomic force microscopes. The findings of this study indicated a decline in maximum dry density and an increase in optimum fluid content in presence of diesel. The compressibility of the soil increased when it was exposed to the organic fluid. Adding diesel content reduced cohesion, internal friction angle and unconfined compressive strength of the soil. Considerable changes of the geotechnical parameters of illite soil in the presence of diesel indicate the necessity of study of the oil-contaminated clayey soils before the implementation of engineering projects.