The effect of light crude oil contamination on the geotechnical properties of kaolinite clay soil

Crude oil is of economic importance to any nation. However its poor management and disposal method has resulted in oil spillage and ground contamination. Most emphasis on crude oil contamination on the environment has been on surface and ground water pollution, as well as plants and animals with little or no attention paid to the engineering properties of the contaminated soil. This research is thus aimed at investigating the effect of light crude oil contamination on the geotechnical properties of kaolinite clay soil. This research is a laboratory based experiment in which the contaminated soil was prepared by adding different percentages of light crude oil (2%, 5%, 8%, 10%, 15% and 20%) measured by weight of the dry soil sample and mixed until a uniform mixture was obtained. The British Standard Test Methods for Civil Engineering purposes BS 1377: 1990 (EUROCODE 7: EN 1997: 2-5) was adopted with few modifications. The calculations were based on the fact that the pore space in the contaminated soil is occupied by water and crude oil so water content was calculated from the fluid content and the rate of evaporation of crude oil during oven drying was also considered. The classification results showed that crude oil contamination caused an increase in linear shrinkage, liquid limit, plastic limit and plasticity index between 0% to 20% contaminations. The compaction result showed that there was an increase in maximum dry density while the optimum moisture content decreased between 0% and 15% of crude oil contamination. The result showed that the soil could not compact at 20% contamination and above. Also, the coefficient of permeability increased with increase in the percentage of crude oil contamination while the coefficient of consolidation value (Cv) increases with increase in the percentage of contamination. There was a decrease in the cohesion value and the frictional angle due to the introduction of the crude oil into the soil. Although crude oil altered the geotechnical properties of the kaolinite clay soil and reduced its strength, the soil can still be used for geotechnical purposed after remediation.