Ibrahim Adewuyi Oyediran - Department of Geology, Faculty of Science, University of Ibadan, Ibadan, Nigeria
Nchewi Ideba Enya - Department of Geology, Faculty of Science, University of Ibadan, Ibadan, Nigeria

Sandy alluvial soils contaminated with crude oil were investigated with a view to understanding the effects of crude oil contamination on their engineering properties. Bulk samples of alluvial soils compacted in layers were admixed thoroughly with ۱۰% by volume of the contaminant and were cured for ۶۳ days under room temperature in the laboratory and outside in the open to simulate field conditions. Mineralogical and chemical compositions of soils were obtained using X-ray diffraction and X-ray fluorescence analyses, and specific gravity, hydraulic conductivity, and compaction tests were conducted on the soils before and after contamination. Results show that the soil is silica-rich with SiO۲ content of ۹۶.۲۴g/g. This is corroborated by the high quartz content (۹۶.۶۲%) observed from the mineralogical composition with minor amounts of kaolinite (۶.۰۴%), and trace amounts of haematite (۰.۰۲%).  The addition of crude oil resulted in an increase in maximum dry density (MDD) with a corresponding decrease in hydraulic conductivity, optimum moisture content (OMC), and specific gravity for both laboratory and outside cured samples. Hence, crude oil contamination can be said to modify the engineering properties of sandy soils, and the environment of samples’ emplacement also contributed to the alteration pattern observed.

Key words: Alluvial, Compaction, Contamination, Crude Oil, Hydraulic conductivity and Specific gravity