A multi-aspect application of microwave radiation on rehabilitating and improving the geotechnical properties of polluted-sand-clay mixture

Abstract

Crude oil products are among the most common pollutants of soils which can drastically affect the engineering properties of soils. In the current study, a series of laboratory tests were conducted to investigate the interaction between crude oil and sandy soil with clay and the effect of crude oil, crude oil residence time, absorbent additives type and content, microwave power, specimen weight, maximum grain size and fine grain fraction on the removal efficiency of pollution through microwave radiation to extract optimum values for potential and high efficiency in hydrocarbon removal. The present study also investigated geotechnical properties, including cohesion, internal friction angle, shear strength in three conditions before and during pollution and after cleanup utilizing direct shear and static triaxial tests. The results showed that the presence of clay particles, oil content and saturation effect in the soil could significantly control the engineering soil behavior. In the presence of 4% crude oil in direct shear tests, the whole oil content is accumulated on clay particles due to the high specific area of clay particles, reducing the cohesion and the internal friction angle. By contrast, beyond the 4% of crude oil, sand particle in the soil was the controlling factor of the whole behavior of the mixture. In triaxial tests, the trend of soil parameters is almost similar to direct shear tests by increasing crude oil, except that, with an increase of 4% of oil, the friction angle of the soil increases due to the presence of a large number of flocculated clay particles.