# Geotechnical Evaluation of Diesel Contaminated Clayey Soil
## 4 Conclusions  
The geotechnical properties of unsaturated diesel-contaminated soil were evaluated and compared with the ones obtained for the soil under natural condition. Diesel concentration in the soil was gradually increased from 0% to 14%; however, the soil could only retain 12.62% \(\pm\) 0.27% of the added diesel, which corresponded to a saturation rate of 79.46% \(\pm\) 1.03%. This result indicated that the soil only retained the necessary diesel to fulfil its hydration demands.  
Diesel contamination of soil reduced its calcium content and caused a decrease in the pH of the soil. Diesel promoted the agglomeration of fine-grain-sized particles of the soil and changed the particle size distribution of the contaminated soil.  
The cohesion of contaminated soil decreased by 20%, while its internal friction angle increased by 30%. Although the matric suction of contaminated soil was considerably lower than the one obtained for natural soil; its osmotic suction was considerably higher. This contributed to an increase in the shear strength of the contaminated soil as compared to the natural soil. However, before considering that the contaminated soil quality improved due to its higher shear strength, the consolidation behavior of the contaminated soil should be assessed.  
Conceptualization, C.E.H.-M.; experiment set up, C.E.H.-M.; investigation, P.G.R. and C.E.H.-M.; writing-original draft, C.E.H.-M.; writing-review & editing, P.G.R., O.C.A. and C.E.H.-M.; project administration, C.E.H.-M.; funding acquisition, C.E.H.-M. and O.C.A. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Consejo Nacional de Ciencia y Tecnologia (CONACYT), grant number 270161, and by the Universidad Autonoma de Queretaro, grant number FIN-2020-03 (FONDEC-UAQ-2019).  
Not applicable.  
Data Available Statement: Data presented is contained within the article.  
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.  
Appendix A Statistical analysis of the concentration of the chemical elements of the soil reported on Table 4. The analysis was executed in Excel for Microsoft 365 with the \"Data analysis\" tool.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multicolumn{2}{c}{**Summary**} & & & & \\ \hline _Groups_ & _Account_ & _Sum_ & _Average_ & _Variance_ & \\ \hline Mg—Natural soil & 3 & 2.887 & 0.962333333 & 0.74157633 & \\ Mg—Contaminated soil & 3 & 1.768 & 0.58933333 & 0.01989033 & \\ \hline ANALYSIS OF VARIANCE & & & & & \\ \hline _Origin of variances_ & _Sum of squares_ & _Degrees of freedom_ & _Mean of squares_ & \(F\) & _Probability_ & _Critical value for F_ \\ \hline Between groups & 0.2086935 & 1 & 0.2086935 & 0.54813562 & 0.500182374 & 7.708647422 \\ Within groups & 1.522933333 & 4 & 0.380733333 & & & \\ Total & 1.731626833 & 5 & & & \\ \hline \hline \end{tabular}
\end{table}
Table 10: Aluminum.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multicolumn{2}{c}{**Summary**} & & & & \\ \hline _Groups_ & _Account_ & _Sum_ & _Average_ & _Variance_ & \\ \hline Ca—Natural soil & 3 & 22.247 & 7.415666667 & 0.02434433 & \\ Ca—Contaminated soil & 3 & 16.195 & 5.39833333 & 0.21904633 & \\ \hline ANALYSIS OF VARIANCE & & & & & \\ \hline _Origin of variances_ & _Sum of squares_ & _Degrees of freedom_ & _Mean of squares_ & \(F\) & _Probability_ & _Critical value for F_ \\ \hline Between groups & 6.104450667 & 1 & 6.104450667 & 50.1617482 & 0.002097894 & 7.708647422 \\ Within groups & 0.486781333 & 4 & 0.121695333 & & & \\ Total & 6.591232 & 5 & & & \\ \hline \hline \end{tabular}
\end{table}
Table 6: Calcium.