# Study on Strength and Microstructure of Red Clay Reinforced by F1 Ionic Soil Stabilizer
## 3 Results and Discussion
### Unconsolidated Undrained Triaxial Compression Test Results  
The shear strength parameter is an important mechanical index of F1 reinforced red clay. As demonstrated in Figure 5, in combination with the UU test results, the (\(\delta_{1}\)-\(\delta_{3}\))\({}_{f}\)-\(\varepsilon\) curve was drawn for red clay samples with different F1 doses. When the confining pressures were 50, 100, 200, and 400 kPa, respectively, the deviator stress of red clay with different F1 contents increased with increasing axial strain, and the relationship between them was approximately hyperbolic. According to the specification [29], when there is no obvious peak, the principal stress difference corresponding to 15% axial strain is taken as the failure stress.  
The relationship between the maximum deviator stress of F1 reinforced red clay and F1 content under various confining pressures is displayed in Figure 6. The maximum deviator stress of F1 reinforced red clay under different confining pressures increased at first and then decreased in response to F1 dose. Clay samples with 0.3 L/m\({}^{3}\) F1 exhibited 1.13-fold, 1.41-fold, 1.50-fold, and 1.12-fold higher maximum deviator stress at 50, 100, 200, and 400 kPa confining pressures, respectively, compared to virgin red clay. Under the same parameters, clay samples with 0.5 L/m\({}^{3}\) F1 exhibited 1.67-fold, 1.69-fold, 1.97-fold, and 1.46-fold higher maximum deviator stress. At an F1 dose greater than 0.5 L/m\({}^{3}\), the maximum deviator stress decreased. According to the analysis results in Table 2, 0.5 L/m\({}^{3}\) was the best F1 dose for reinforced red clay.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**F1 Dosage/L-m\({}^{-3}\)** & **Plastic Limit/\%** & **Liquid Limit/\%** & **Plasticity Index** & \begin{tabular}{c} **Optimum** \\ **Moisture** \\ **Content/\%** \\ \end{tabular} & \
\begin{tabular}{c} **Maximum Dry** \\ **Density/g-m\({}^{-3}\)** \\ \end{tabular} &
\begin{tabular}{c} **Permeability** \\ **Coefficient/cm-s\({}^{-3}\)** \\ \end{tabular} \\ \hline
0 & 18.8 & 43.8 & 22.6 & 19.76 & 1.71 & \(15.72\times 10^{-9}\) \\
0.3 & 24.0 & 41.4 & 19.8 & 21.34 & 1.74 & \(9.32\times 10^{-9}\) \\
0.5 & 27.4 & 40.1 & 12.7 & 22.18 & 1.81 & \(9.15\times 10^{-9}\) \\
0.7 & 24.8 & 41.3 &Figure 6: Relationship between maximum deviator stress of red clay and F1 content.  
The molar stress circle of F1 reinforced loess sample under different confining pressures at the time of failure was drawn, and the cohesion \(c\) and internal friction angle \(\varphi\) of reinforced red clay with different F1 doses were obtained as illustrated in Figure 7. The cohesion and internal friction angle of red clay initially increased and then decreased alongside the F1 dose. The 0.3 L/m\({}^{3}\) F1 clay exhibited 1.32-fold higher cohesion and 1.12-fold higher internal friction angle, while the 0.5 L/m\({}^{3}\) F1 clay exhibited 1.64-fold higher cohesion and 1.30-fold higher internal friction angle. The increase in cohesion and internal friction angle was because F1 can effectively reduce particle spacing and water film thickness, thereby increasing cohesion and soil compactness and, in turn, increasing the soil's shear strength parameters.