Wastewater contamination of fine-grain soils in urban aquifers leads to considerable changes in chemical, physical, and strength properties of this type of soil. This phenomenon is important because the contamination of foundation soils in an urban area by rising of the water table due to infiltration of wastewater may result in the loss of soil strength and structural damage. The main purpose of this study is investigation of the influence of wastewater contaminants on the geotechnical properties of a silty clay sampled from the central part of Mashhad city in northeast of Iran. For this propose, different tests including Atterberg limits, electrical conductivity, resistivity, and unconfined uniaxial compressive strength were carried out on the 148 original and artificially contaminated samples. Samples saturated with various wastewater concentrations of 0, 10, 50, and 100% and duration of 0, 4, 6, and 9 months. The results showed that increase of the wastewater concentration and saturation period leads to decrease in UCS, electrical resistivity, and EC, while Atterberg limits and PH increase.

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