# Experimental Study on the Bearing Capacity of Gas Oil-Contaminated Coastal Sand
## 2 Laboratory Investigation  
### Materials  
A typical fine-grained, gap-graded coastal sand was selected to be used in this study. The physical properties of the sand and its grain size distribution are presented in \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Research** & **Average Particle Size, D50 mm** & **Contamination Type** & **Classification (Unified)** & **Bearing Capacity** & **CBR** & **Friction Angle** & **Cohesion** \\ \hline [PERSON] et al. (1995) [2] & 0.43 & \begin{tabular}{c} Heavy and \\ Light Crude \\ Oil, Benzene, \\ Gas Oil \\ \end{tabular} & SP & - & Increase * & Decrease & - \\ [PERSON] and [PERSON] (1998) [16] & 0.04 & Crude Oil & Sand & - & - & Decrease & Increase * \\ [PERSON] and [PERSON] (2001) [7] & 0.6 & \
\begin{tabular}{c} Oman Crude \\ Oil \\ \end{tabular} & SP & Decrease & - & Decrease & - \\ [PERSON] et al. (2007) & 0.28 &
\begin{tabular}{c} SP \\ Cride Oil \\ \end{tabular} & SP & - & - & Decrease & Increase * \\ [PERSON] et al. (2013) [15] & 0.01 & Crude Oil & SP & Increase * & - & Decrease \\ Alhassan and Fagge (2013) & 100\% \(<\) 0.315 mm & LFPO & SC & - & Decrease & Shear Strength: Constant \\
[19] & 82\% \(<\) 0.315 mm & Vacuum Gas & Laterite & Increase * & Shear Strength: Increase * \\ Akinwumi (2014a) [17] & 0.05 & Nigerian & Sandy Lean & - & Increase * & - & - \\ Akinwumi (2014b) [18] & 0.05 & Crude Oil & Clay & - & Increase * & - & - \\  & 0.6 & \
\begin{tabular}{c} SP \\ SP \\ \end{tabular} & - & - & Decrease & Increase * \\ [PERSON] et al. (2015) [13] & 0.035 & Gas oil & ML & - & - & Decrease & Increase \\ Abtahi and Boushehrian & 0.026 &
\begin{tabular}{c} CL \\ \end{tabular} & - & - & Decrease & Increase \\ Abtahi and Boushehrian & 1.2 & Gas oil & SP & Decrease & - & Decrease & Increase \\ (2020) [10] & 1.2 & Kerosene & SP & Decrease & - & Decrease & Increase \\ Keerravi (2019) [22] & 0.36 & Gasoline & SM & Decrease & - & Decrease & Increase * \\ Joukar and Boushehrian & 1.2 & Gas oil & SP & Decrease & - & Decrease & Increase \\ (2020) [9] & 1.2 & Kerosene & SP & Decrease & - & Decrease & Increase \\ Ahmadi and Ebadi (2021) & \(\approx\)0.2 & SP-SC & - & - & Decrease & Increase \\
[14] & \(<\)0.2 & Crude Oil & SC-SM & - & - & Decrease & Increase \\  & \(<\)0.2 & CL-ML & - & - & Increase & Increase * \\ \hline \hline \end{tabular}  
* Increase to a specific saturation level, and then a decrease.  
\end{table} 
Table 1: A summary of studies on geotechnical properties of hydrocarbon-contaminated soils. Table 2 and Figure 2, respectively. The Chamkhale sand (from the coastline of the Caspian Sea) is classified as poorly graded (SP) according to the Unified Soil Classification System. The median particle size of the sand (i.e., D50) is 0.175 mm; therefore, no particle size effect on the results of the physical modeling is expected, as it provides a footing width (B) to median particle size (B/D50) of greater than 850, which is well above the minimum ratio recommended for avoiding possible particle size effects [30]. Drawing from records of hydrocarbon contaminations that occurred on the west coast of the United States between 2002 and 2015, [PERSON] and [PERSON] [31] identified gas oil as one of the most prevalent ground pollutants. Consequently, in our current study, we have selected gas oil as the focus of our soil contamination investigation. The key properties of gas oil are outlined in Table 3 for reference. guidelines. Before placing the soil into the box, the sand was mixed with a specific gravimetric gas oil content to achieve the desired level. To account for evaporation and gas oil loss during preparation, a slightly greater amount of gas oil was added to the mixture. After transferring the soil samples into the shear box, we employed the wet-tamping method to achieve specific relative densities of 30% and 70% at varying initial degrees of saturation. The control of the relative densities was accomplished through precise measurements of the specimen height in the direct shear box for a given specimen weight.