## 3 Analysis of the Tensile Strength  
### Stress-Strain Curve  
The longitudinal stress-strain curves of sandstone samples with different bedding angles and strengths were drawn as shown in Figure 3. It can be seen from the figure that the longitudinal stress-strain curves of the sandstone samples in each group have similar changing trends, which have experienced an elastic deformation stage, yield stage, brittle failure stage, and residual failure stage. The curves are all straight lines at the beginning, and the stress and strain are proportional, in contrast to the experimental results of previous scholars. This is because there is a compaction stage in the conventional experimental compression process, and the compression structure of sandstone samples is denser under the action of the pressure head, so the curve is an arc curve rather than a straight line. With the continuous loading of displacement, the slope of the curve decreases somewhat, but it is not obvious. When the peak value is reached, the curve drops sharply. Brittle failure occurs in the sandstone sample at this time, and then it enters the residual failure stage, at which point the whole failure process ends. The slope of the curve decreases with continuous displacement loading, but it is not very obvious; when the peak is reached, the curve drops steeply; obviously, the sandstone specimen suffers brittle damage at this time, and then after entering the residual damage phase, to the end of the entire damage process. \begin{table}
\begin{tabular}{c c c} \hline
**Number of Bedding Plane** & **Left Vertex Coordinates** & **Right Vertex Coordinates** \\ \hline
1 & (0.0004, 0.0094) & (0.0206, 0.0296) \\
2 & (0.0002, 0.0084) & (0.0216, 0.0298) \\
3 & (0.0031, 0.0050) & (0.0279, 0.0298) \\
4 & (0.0040,  
Figure 3: \(Cont.\)  
Figure 3: _Cont._  
By comparing the stress-strain curves of ultra-weak bedding (bedding strength of 0.3 times the sandstone strength), weak bedding (bedding strength of 0.6 times the sandstone strength), strong bedding (bedding strength of 1.5 times the sandstone strength), and homogeneous sandstone (bedding strength of 1 times sandstone strength), we found the following: (1) With the change in the bedding angle, the strength of the ultra-weak sandstone decreases obviously. However, the variation is not linear; from 0\({}^{\circ}\) to 15\({}^{\circ}\), the variation range is small, but when the bedding angle is greater than 30\({}^{\circ}\), the strength of the ultra-weak sandstone decreases sharply, to only half of the strength of homogeneous sandstone, and reaches the minimum value at 60\({}^{\circ}\), which is about 1/3 of the strength of the homogeneous sandstone. The observation of the strain value of sandstone when the fracture occurs shows that the strain of homogeneous sandstone is about 1% when the fracture occurs, while that of the ultra-weak sandstone is 0.85% when the bedding angle is 0\({}^{\circ}\) and drops to 0.6% when the bedding angle is 30\({}^{\circ}\), and then decreases slowly with the increase in the angle until it reaches the minimum value at 60\({}^{\circ}\); when the strain is less than 0.4%, the sandstone has fractured. (2) With the increase in the angle of the bedding, the change in the strength of the weakly bedded sandstone is relatively small, and there is an obvious weakening of the strength only after 45\({}^{\circ}\), and the weakening is significantly smaller than that of the ultra-weak bedded sandstone; the strength of the weakly bedded sandstone decreases by 20% compared with that of the homogeneous sandstone, but it is also far beyond that of the ultra-weakly bedded sandstone, at about 1.5-2 times the strength of the latter. At the same time, the change law of strain and the strength of different layer angles are essentially the same. (3) Strong sandstone (bedding strength of 1.5 times that of sandstone) has no strength difference from homogeneous sandstone, which is somewhat stronger than the mean strength of sandstone.