## 3 Mechanical Properties Analysis  
### Stress-Strain Curve Features  
The overall results of the laboratory tests are shown in Table 1. Due to small data deviations, the subsequent analysis was carried out by taking the average value or eliminating the abnormal value. The typical differential stress-axial strain curves under different confining pressures are shown in Figure 5, where \(\sigma_{1}\) is axial stress, \(\sigma_{3}\) is confining pressure, (\(\sigma_{1}\)-\(\sigma_{3}\)) is differential stress, and \(\epsilon_{1}\) is axial strain. The curves can be divided into the initial compaction stage (upper concave section), elastic deformation stage (straight line section), plastic deformation stage (non-linear section before peak value), and post-peak strain-softening stage. As the  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**No. **} & \multirow{2}{*}{ \begin{tabular}{c} **Confining** \\ **Pressure** \\ **(MPa)** \\ \end{tabular}  } & \multirow{2}{*}{ \begin{tabular}{c} **Water** \\ **Content (\%)** \\ \end{tabular}  } & \multirow{2}{*}{ \begin{tabular}{c} **Peak Differential** \\ **Stress (MPa)** \\ \end{tabular}  } & \multirow{2}{*}{ \begin{tabular}{c} **Average Peak** \\ **Differential Stress** \\ **(MPa)** \\ \end{tabular}  } & \multirow{2}{*}{\ \begin{tabular}{c} **Elastic Modulus** \\ **(GPa)** \\ \end{tabular}  } & \multirow{2}{*}{ \begin{tabular}{c} **Average Elastic** \\ **Modulus (GPa)** \\ \end{tabular}  } \\ \hline
1-1 & & 0.180 & 147.0 & & 31.84 & \\
1-2 & 0 & 0.204 & 141.0 & 146.0 & 31.09 & 31.36 \\
1-3 & & 0.184 & 149.0 & & 31.14 & \\
2-1 & & 0.190 & 191.4 & & 39.85 & \\
2-2 & 5 & 0.186 & 190.1 & 190.8 & 37.82 & 38.84 confining pressure increases, the initial compaction stage becomes smaller and smaller, indicating that the sample becomes denser under the action of confining pressure. With the increase in confining pressure, the plastic deformation stage before the peak becomes longer, indicating that the plastic properties of the sample are obvious with an increase in the confining pressure. The peak differential stress increases and the peak axial strain slightly increases with an increase in the confining pressure, indicating that an increase in the confining pressure makes the strength of the rock gradually increase. The granite samples showed obvious brittle failure under low confining pressure. When the confining pressure was 0 MPa, the peak strain of the sample was 0.60-0.65% and the peak axial stress was between 141-149 MPa. When the confining pressure was 5 MPa, the peak axial strain of the sample was 0.63-0.72% and the peak differential stress was between 190-192 MPa. As shown in Figure 5, under the condition of low confining pressure, as the confining pressure increased, the initial compaction stage became significantly smaller. That is, the initial concave part of the curve became significantly smaller. The granite exhibits characteristics of plastic failure under medium and high confining pressures. When the confining pressure was 10 MPa, the peak axial strain of the sample was 0.70-0.90% and the peak differential stress was 224-226 MPa. When the confining pressure was 15 MPa, the peak axial strain of the sample was 0.91-1.00% and the peak differential stress was 261-265 MPa. When the confining pressure was 20 MPa, the peak axial strain of the sample was 0.92-1.03% and the peak differential stress was 280-292 MPa. As shown in Figure 5, as the confining pressure increased, the initial compaction stage gradually decreased; that is, the initial upward concave part of the curve in Figure 5 gradually decreased; as the confining pressure increased, the peak axial strain of the sample gradually increased and the peak differential stress increased significantly. The microcracks in the sample were compressed gradually and closed, resulting in nonlinear deformation. As shown in Figure 5, the sample did not reach peak strength. It will be destroyed immediately but lost its bearing capacity once the strength decreased slightly.