A GEOTECHNICAL STUDY ON TWO SELECTED OIL-CONTAMINATED SOIL SITES

Abstract

Oil contamination in soil represents a significant environmental challenge affecting soil properties and leading to a reduction in soil efficiency for use in engineering applications. To cover this gap of knowledge, the investigated soil in this study is an actual polluted soil taken from the Sabba oil field and the Nasiriyah oil field, which are both located in Thi-Qar Governorate, south of Iraq. The study aimed to provide realistic data showing the impact of oil contamination on the geotechnical behavior of soil. Two disturbed polluted samples were collected from a depth of 30-40 cm from oil field sites. The first sample corresponding to the Nasiriya oil field was named soil (A), while the second sample corresponding to the Sabba oil field was named soil (B). A series of lab experiments was executed on a contaminated soil, including particle size distribution, specific gravity, Atterberg limits, standard compaction, pH test, and vane shear test. It concluded that soil (A) was finer than soil (B). The maximum dry density of fine soil (soil A) was less than that of the coarser soil (soil B); oppositely, the optimum moisture content of soil (A) was far greater than that of soil (B). The results of the liquid limit, plastic limit, plasticity index, and specific gravity of both soils fit very well with previous literature. Since soil (B) was more polluted than soil (A), the pH value obtained for soil (B) was less than that of soil (A). Also, the pH of soil (A) decreases after washing with water for several weeks; that could reflect the inefficiency of soil washing as a treatment technique without using chemicals. The findings of the vane shear experiment, which was accomplished for soil (A), show that the undrained shear strength (Cu) is 20 kPa, which can be considered a moderate value. The outcomes of the tests, including particle size, liquid limit, plastic limit, plasticity index, specific gravity, pH, and undrained shear strength of both contaminated soils, are very well consistent with similar previous laboratory work and could be attributed to the degree of pollution and the soil texture.