Investigation of engineering geological behavior of surface oil hydrocarbons contaminated soils in Tabriz oil refinery area

Infiltration of oil materials into the soils has environmental impacts and changes engineering geological properties of soils. This paper has investigated the engineering geological behaviour of contaminated soils from the Tabriz Oil Refinery. The oil materials contaminations were alkenes hydrocarbon that had more than 14 carbon atoms (C14) and is classified in the solid – phase. Based on the results of particle size analysis, there were two types of contaminated soils including silty sand (SM) and lean clay (CL). The results of Atterberg test on CL sample show that the plasticity index (PI) decreased for more contamination and all of SM samples were none plastic. In standard compaction tests, the samples with more contamination was reached to maximum dry unite weight in lower optimum water content. Also, the CBR test results show that with increase of contamination, the CBR was decreased and the reduction for CL sample was more than the SM sample. Based on obtained data from direct shear and consolidation tests, the shear strength parameters (cohesion and internal friction angle) were decreased and the consolidation settlement was increased, respectively.