Influence of Gas Oil Contamination on Geotechnical Properties of Fine and Coarse-Grained Soils

Contamination of soil by the leakage of gas oil may affect its physical, chemical and mechanical properties. There are many ways which could enhance the leakage of gas oil including; corroded storage tanks, processing plants and petroleum transportation. The aim of this paper is to consider the effect of gas oil contamination on the geotechnical properties of some soil specimens such as poorly graded sand (SP), low plasticity clay and silt (CL, ML). The uncontaminated specimens have undergone some basic laboratory tests such as plasticity, compaction, unconfined compression strength (UCS) and direct shear tests. The samples artificially contaminated with 3, 6 and 9 % of gas oil in relative to their dry weight. Results indicate a decrease in the friction angle and an increase in the cohesion of the soils with the increase of gas oil content. In addition, a reduction in the maximum dry density and optimum moisture content observed during the conduction of compaction test. The increase of gas oil percentage also showed a direct effect on the increases of liquid and plastic limits of clay and silt soils. On the other hands, the increase of gas oil percent reversely effect on the UCS of silt soil. According to the field emission scanning electron microscopy study, it can be stated that the increase of clay particles extends the rate of fabric flocculation is a key factor for increasing the unconfined compression strength in clayey soil.