Effect of Crude Oil Contamination on Compaction and Consistency of Some Clay Soils from Parts of Yenagoa, Bayelsa State, Nigeria

Abstract

Bayelsa state is the southernmost part of the crude oil prolific Niger Delta region of Nigeria where oil exploration and exploitation activities have resulted to the pollution of its land, water, and air. Most parts of the area have experienced crude oil contamination of one form or the other, and the effects on man and the ecosystem are wide ranging. This study has examined the effect of oil contamination on the compaction behaviour of two clay samples obtained at shallow foundation depths in Yenagoa. The two clay samples, A and B are classified according to the unified soil classification system (USCS) as high plasticity inorganic sandy fat clay, and sandy lean clay, respectively. 4, 8, and 12 % crude oil by mass of dry soil were used to mix with the soil samples and left to cure in plastic bags for 48 hours before testing. In sample B, liquid limit (LL) was found to increase by about 9% for all proportions of crude oil while plastic limit (PL) was increased by 13%, 15%, and 27% for 4, 8, and 12 % oil content, respectively. These increase in LL and PL also brought about an increase in plasticity index except for 12% crude oil treatment. However, in all, a low plastic soil was changed to a slightly high plastic one as plotted on the Casagrande chart. The maximum dry density (MDD) of the two samples was also reduced by oil contamination with an increasing oil content exacerbating the reduction of MDD. It is therefore, recommended that care be taken during construction when dealing with clay soils within a potential crude oil contaminated region.