Clay soil behaviour due to long-term contamination by liquid petroleum fuels: microstructure and geotechnical properties

The article presents the results of qualitative and quantitative microstructural analysis, and the basic properties of clay soils subjected to long-term contamination by liquid petroleum fuels (LPF). Comparative study of undisturbed, contaminated in situ clay soil (CS) and reference uncontaminated soil (US) was performed. Soil contamination by these compounds causes transformation of microstructure and changes of geotechnical parameters. Microstructure is a key factor in the interpretation of soil properties. Microstructural analyses were performed with application of scanning electron microscope (SEM) and STIMAN software. It was estimated that contaminated soil is characterised by lower moisture content, plasticity, pH and zeta potential, and by higher bulk density and consistency index. Due to hydrocarbon contamination, soil microstructure changed from highly anisotropic mixed laminar-turbulent into uniform matrix type. Comparative quantitative analysis of the microstructure indicated redistribution of the pore space expressed by changes in porosity, pore number and shape, decrease of microporosity, and increase of elongated mesopores number.