Geotechnical Properties of Plastic Marl Contaminated with Diesel

The reported study was conducted to assess the geotechnical properties of plastic marl contaminated with diesel. The geotechnical properties of the uncontaminated soil, including gradation, Atterberg limits, compaction characteristics, angle of internal friction, cohesion and unconfined compressive strength (q_u) , were initially evaluated. Thereafter, the soil was contaminated with four dosages of diesel (3, 6, 9 and 12% by weight of the dry soil) and the changes in the geotechnical properties, due to the contamination, were assessed. The liquid limit increased with an increase in the contamination level of up to 9%. A further increase in the contamination level decreased the liquid limit. A similar trend was noted in the plasticity index. However, no significant changes were noted in the compaction characteristics, namely the maximum dry density and optimum moisture content. A large increase in the unconfined strength was measured in the soil contaminated with 3% diesel. However, the strength decreased up to 9% contamination and thereafter an increase in this strength was noted. A similar trend was noted in the cohesion value. This trend in the unconfined compressive strength and cohesion may be ascribed to the agglomeration of soil particles at low contamination levels, while the lubrication effect dominates at high contamination levels, as noted in the scanning electron micrographs. Energy-dispersive X-ray spectroscopy analysis was carried out to measure the elemental composition of the contaminated soil, and a high percentage of carbon was observed as an indication of the presence of hydrocarbons.