# Geotechnical Evaluation of Diesel Contaminated Clayey Soil
## 2 Materials and Methods
### Test Methods  
The evaluated properties of the soil are summarized in Table 2 and were executed as indicated in the corresponding standards. The \"water content\" of the contaminated soil was obtained by applying the same standard used for the natural soil. However, the term \"water content\" was transformed to \"liquids content\" to consider the difference in specific gravity between diesel and water [17].  
To determine the modified free swell index (MFSI) for both soil conditions, 10 g of oven-dried (\(105\pm 1\)\({}^{\circ}\)C) soil passing a No. 40 (425 \(\upmu\)m) sieve were poured into a 100-mL graduated cylinder filled with distilled water. The soil was manually mixed with the distilled water and left undisturbed for the soil to swell/settle and achieve an equilibrium state of volume. The MFSI was calculated as the ratio of the equilibrium sediment volume to the dry weight of the oven-dried soil.  
The liquid limit was evaluated by the fall cone method as indicated in the standard procedure adopted. Distilled water was gradually added to the soil--both natural and contaminated--to obtain a semiliquid consistency. The soil and the added water were thoroughly mixed until a homogeneous mass was obtained. This mass was poured into a sealed container. It was stored in the controlled-temperature chamber for 24 h to allow the added water to permeate through the soil before the cone penetrometer tested the sample. For both soil conditions, the liquid limit was evaluated by considering the equivalent water content of the samples.  
The direct shear test was executed in a 100 mm \(\times\) 100 mm shear box at a shear velocity of 1 mm/min. Normal stresses applied were 50, 100, and 200 kPa. Matric and total suction  
\begin{table}
\begin{tabular}{c c} \hline
**Parameter** & **Value** \\ \hline Flash point (\({}^{\circ}\)C) & \(\geq\)45 \\ Density (kN/m\({}^{3}\)) & 8.16 \\ Specific gravity & 0.832 \\ Kinematic viscosity at 40 \({}^{\circ}\)C (mm\({}^{2}\)/s) & 1.9-4.1 \\ Cetane index & \(\geq\)48 \\ Sulfur content (ppm) & \(<\)500 \\ Aromatics content (\%, in volume) & \(\leq\)30 \\ Water and sediments (\%, in volume) & \(\leq\)0.05 \\ \hline \end{tabular}
\end{table}
Table 1: Applied diesel fuel specifications [14].  
of the soils were evaluated by the filter paper method, using the calibration curves for wetting the filter paper, Whatman No. 42.  
The pH and the electrical conductivity (EC) of the soils were measured with a pH/EC/DO/ISE multiparameter (Orion Versa Star Pro, Thermo Scientific, Waltham, MA, USA) with automatic temperature compensator, equipped with a glass electrode for pH measurements and an EC sensor. Before each natural and contaminated soil sample set's pH measurement, the equipment was calibrated with the traceable to the National Institute for Standards and Technology (NIST) buffer solutions of pH 4, pH 7, and pH 10 obtained from Thermo Fisher. The equipment calibration was repeated until a correlation coefficient of the calibration curve of the multiparameter was at least of 0.98. For the EC measurements the equipment was calibrated with the traceable to NIST standard solutions of 100 \(\mu\)S/cm and 1413 \(\mu\)S/cm obtained from Thermo Fisher (Austin, TX, USA).