Environmental constraints in providing landfills and pollution purgation of organic matter such as petroleum hydrocarbons from soil and water and optimum use of wastes need to provide modern and practical guidelines for improving soil quality. In this study, interaction effects of petroleum hydrocarbons and rice husk ash and coal ash amendments on soil mechanical properties was studied. oil from Isfahan refinery complex (Bakhtiardasht) with 0, 2 and 4% (by weight) pollution was used after passing through 2 mm sieve. Rice husk ash (RHA) and coal ash (a mixture of fly ash (FA) and bottom ash (BA) at a ratio of 1: 1) in three levels of 0, 4 and 8% by weight was mixed with contaminated and non-contaminated soils. The mixtures were put in 1 kg pots and incubated for 120-day with specified irrigation period then plasticity limit (PL), liquid limit (LL) and the shrinkage limit (SL) were measured. Penetration resistance (PR), compressibility index (Cc) and indirect tensile strength (TS) of Brazilian method was measured, as well. The results showed that with increasing petroleum hydrocarbons concentration, the Atterberg limits fell (excepted for shrinkage limit). With increasing the level of pollution up to 2%, LL and PL decreased significantly (from 11.8 to 4.3% respectively). Compressibility index (Cc) increased by the pollution level to 2%, but achieving pollution level up to 4%, caused a significantly decreasing in compressibility. The larger coal ash particle caused a higher friction reduction in soil compressibility. Cone Index (CI) decreased with increasing the levels of pollution (40.8% comparing 0 to 4% contaminants) and significantly increased with higher levels of ash. Also, by increasing the amount of ashes from 4 to 8%, the cone index increased by 43.03%. The results of tensile strength test (ITS) showed that with increasing pollution up to 2%, tensile strength increased by 15.7% but by achieving pollution to 4%, decreased by 150%. With increasing pollution levels to 4% cohesion between the particles reduced and so the soil resistance decreased. In general, petroleum hydrocarbons, rice husk ash and coal ash caused significant changes in mechanical properties and consistency limits. Keywords : Petroleum hydrocarbons, Rice husk ash, Coal ash, Atterberg limits, Penetration resistance, Cone index, Soil compressibility, In-direct tensile strength