## 2 Experimental Materials and Methods
### Laboratory Tests
#### 2.3.2 Geotechnical Properties  
Geotechnical properties of the soil before and after treatments were estimated in the physical and mechanical aspects; physical properties (Afterberg limits, particle-size  
\begin{table}
\begin{tabular}{l l} \hline \hline
**Descriptions** & **Conditions** \\ \hline GC Instrument/Detector & Varian, 450-C/300-MS \\  & Agilent CP-Sil 8 CB; \\ Column & Ultra-2 (Cross-linked 5\% phenyl methyl silicon) \\  & Injection 300 \({}^{\circ}\)C \\ Temperature & Detector FID 320 \({}^{\circ}\)C \\  & 12 \({}^{\circ}\)C/min rate to 310 \({}^{\circ}\)C for 18.33 min hold \\ Carrier gas/flow rate & Helium (2.0 mL/min) \\ Injection volume & 2 \(\mu\)L \\ Split ratio & 10:1 \\ Ultrasonic extractor model & Bandelin, Sonoplus UW3100 \\ Type of filters & ADVANTEC, Quantitative Filter Paper 5B 110 mm \\ \hline \hline \end{tabular}
\end{table}
Table 6: Descriptions and conditions of gas chromatography (GC).  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Treatment Temperature (\({}^{\circ}\)C)** & **Treatment Time (min)** & **Residual TPH Concentration (mg/kg)** & **Removal Efficiency (\%)** \\ \hline  & 0 & \({}^{\
abla}\) 26,063 & - \\  & 5 & 5490 & 78.3 \\
400 & 10 & 2866 & 88.7 \\  & 15 & 1846 & 92.7 \\  & 0 & 25,325 & - \\
500 & 5 & 3626 & 85.7 \\  & 10 & 1995 & 92.1 \\  & 15 & 1383 & 94.5 \\  & 0 & 26,600 & - \\
600 & 5 & 2512 & 90.6 \\  & 10 & 652 & 97.6 \\  & 15 & 38.2 & 99.9 \\ \hline \hline \end{tabular} \({}^{\
abla}\) Calculation procedures are shown in Tables A1 and A2.  
\end{table}
Table 5: Residual TPH concentration and removal efficiency by treatment temperature and time.  
distribution, permeability, maximum dry density and optimum moisture content, etc.) related to the movement process of the pollutants and mechanical properties (cohesion and internal friction angle) were concerned with soil stability.  
Attereberg limits are defined as critical water contents of fine-grained soil (silt and clay). Soil appears in one of liquid, plastic, semisolid and solid states depending on its water content, and water contents at the boundary between each state are known as Atterberg limits, which are divided into the liquid limit, plastic limit and shrinkage limit (ASTM D-4318) [31].  
Sieve analysis is often used for determining particle-size distribution of coarse-grained soil. A set of sieves is used to measure particle-size distribution defined as relative weight amount of soil particles remaining in a sieve in % (ASTM D-6913) [28].  
The constant head permeability test (ASTM D-2434) was the method used to identify the relationship between water level variation and time elapsed when the water penetrates the soil sample with a certain diameter and length [33].  
The compaction test (ASTM D-698) was the method used to improve the soil properties by increasing the density using artificial energy. In the process of testing, the air in the voids is discharged when tamping the soil so that the density is increased, and the ratio of void between particles is decreased. Plotting the values of dry density on the y-axis and the moisture contents on the x-axis through a series of compaction tests, maximum dry density and optimum water content can be easily determined from the smooth compaction curve connecting the plotted points [30].  
Direct shear test (ASTM D-3080) determines the shear strength of soil under the consolidated drained condition. The test was performed by horizontally deforming a soil specimen at a controlled strain rate, each under a different normal load condition. Using the Mohr-Coulomb failure envelope, indicating the relationship between shear strain and maximum shear stress, shear strength (cohesion and internal friction angle) of the soil was finally determined [38].