## 3 Results and Analysis
### Anisotropic Mechanical Properties of Lamellar Shale  
Figure 3 shows the complete stress-strain curves of the dry samples of lamellar shale and bedding shale [32]. The complete stress-strain curves of dry lamellar shale samples are obtained by testing the samples for \(\beta\) = 0\({}^{\circ}\), 30\({}^{\circ}\), 60\({}^{\circ}\) and 90\({}^{\circ}\), respectively, under confining pressure of 15 MPa. The complete stress-strain curves of dry bedding shale samples are obtained by testing the samples for \(\beta\) = 0\({}^{\circ}\), 30\({}^{\circ}\), 45\({}^{\circ}\), 60\({}^{\circ}\) and 90\({}^{\circ}\), respectively, under confining pressure of 10 MPa. The complete stress-strain curves of both lamellar shale (Figure 3a) and bedding shale (Figure 3b) present a significant elastic deformation characteristic with a long elastic strain increment. Their differences are mainly manifested in: (1) The compaction stage of bedding shale is not obvious, while the compaction stage of lamellar shale is significant, especially for the sample with \(\beta\) = 90\({}^{\circ}\). This may be due to the fact that more fractures and larger interfaces near the rock matrix and clay minerals in the lamina can lead to a significant micro-fracture closure process in the early loading stage. (2) The residual stress of the lamellar shale after the failure decreases slower with the increase in strain compared with that of the bedding shale. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**No.**} & \multirow{2}{*}{**Sample Types**} & **Axial Direction and** & \multicolumn{3}{c}{**Compressive Strength (MPa)**} & \multicolumn{3}{c}{**Elastic Modulus (GPa)**} \\ \cline{3-8}  & & **Lamina (Bedding)** & **Dry** & **24-h Hydration** & **48-h Hydration** & **Dry** & **24-h Hydration** & **48-h Hydration** \\  & & **Angles (\({}^{\circ}\))** & **Samples** & **Samples** & **Samples** & **Samples** & **Samples** \\ \hline
1 & 0 & 116.18 & 102.63 & 97.43 & 16.51 & 15.46 & 14.69 \\
2 & 30 & 107.33 & 96.56 & 92.95 & 12.55 & 11.44 & 10.73 \\
3 & Bedding shale & 60 & 119.45 & 109.21 & 103.54 & 12.12 & 11.19 & 10.03 \\
4 & 90 & 123.54 & 113.71 & 110.21 & 11.83 & 10.76 & 9.88 \\ \hline
1 & 0 & 83.49 & 76.94 & 73.18 & 12.31 & 10.91 & 9.72 \\
2 & 30 & 71.21 & 61.17 & 57.34 & 9.07 & 8.11 & 7.65 \\
3 & Lamellar shale & 60 & 83.12 & 73.41 & 69.97 & 8.79 & 7.74 & 6.96 \\
4 & 90 & 94.91 & 81.14 & 78.13 & 8.47 & 7.32 & 6.84 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Uniaxial compression test results. Comparing the complete stress-strain curves of the lamellar shale samples for each \(\beta\), it is found that the compaction stage is more obvious and the elastic deformation stage is shorter when \(\beta\) is closer to 30\({}^{\circ}\). For example, when \(\beta\) = 30\({}^{\circ}\), the axial strain increments in the compaction stage and the elastic deformation stage are 0.26% and 0.69%, respectively; when \(\beta\) = 0\({}^{\circ}\), the axial strain increments in the compaction stage and the elastic deformation stage are 0.17% and 0.87%, respectively. This indicates that lamellar shale would be more like elastic and brittle rock while \(\beta\) is closer to 0\({}^{\circ}\) or 90\({}^{\circ}\), and would be more like plastic rock when \(\beta\) is closer to 30\({}^{\circ}\). This may be due to the fact that while \(\beta\) is closer to 30\({}^{\circ}\), shear failure would be more likely in the clay minerals lamella. In this case, the rock would present a plastic deformation because of that the deformation and failure of the lamina mainly show plastic characteristics due to that it is mainly composed of silty, tufaceous or argillaceous minerals. Figure 4 shows the change curves of the compressive strengths (deviatoric stresses) of dry shale samples with various \(\beta\). From Figure 4, it can easily be seen that the confining pressure has a great influence on the compressive strength of lamellar shale, showing that the greater the confining pressure is, the higher the compressive strength will be.