# Anisotropy and Directivity Effects on Uniaxial Compression of Carbonaceous Slate Form Jinman Mine
## 3 Results and Discussion
### Loading Effect of Mechanical Parameters
#### 3.2.1 Effect of Slate Structure on Peak Strength  
The peak strength for vertical loading and parallel loading conditions were evaluated based on the results of uniaxial compression tests of different slate samples as shown in Figures 4 and 5. As observed in Table 1, the overall rock structure stability is relatively high due to the series relationship of the slate structure due to vertical loading. The peak strength of the gray samples at fracture is 45.02-63.45 MPa and the average peak strength is 58.34 MPa. The peak strength of the cinerous samples is 22.41-70.19 MPa, with an average peak strength of 53.93 MPa which is approximately 92.44% of gray samples. The expansion \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Sample** & \(\sigma_{c}\)**/MPa** & \(\sigma_{cd}\)**/MPa** & \(E\)**/MPa** & \(\epsilon_{zz}\times\mathbf{10^{-4}}\) & \(\epsilon_{xx}\times\mathbf{10^{-3}}\) & \(\epsilon_{yy}\times\mathbf{10^{-3}}\) & \(\epsilon_{\
u}\times\mathbf{10^{-3}}\) \\ \hline No. 1 Gray sample & 53.26 & 39.03 & 40.55 & 3.27 & \(-\)0.061 & \(-\)0.886 & \(-\)0.620 \\ No. 2 Gray sample & 55.43 & 43.56 & 88.55 & 6.26 & \(-\)0.570 & \(-\)2.691 & \(-\)2.635 \\ No. 3 Gray sample & 47.95 & 28.99 & 54.70 & 5.11 & \(-\)0.623 & \(-\)2.879 & \(-\)2.991 \\ No. 4 Gray sample & 34.15 & 29.52 & 41.14 & 5.78 & \(-\)0.071 & \(-\)0.670 & \(-\)0.163 \\ Average & 47.70 & 35.28 & 56.24 & 5.11 & \(-\)0.331 & \(-\)1.782 & \(-\)1.602 \\ \hline No. 1 Cinerous sample & 54.88 & 48.89 & 41.11 & 1.44 & \(-\)0.035 & \(-\)3.507 & \(-\)3.398 \\ No. 2 Cinerous sample & 28.92 & 23.73 & 62.08 & 1.50 & \(-\)0.087 & \(-\)3.182 & \(-\)3.119 \\ No. 3 Cinerous sample & 50.52 & 46.38 & 78.28 & 1.58 & \(-\)0.020 & \(-\)1.892 & \(-\)1.854 \\ No. 4 Cinerous sample & 12.98 & 8.64 & 50.62 & 1.29 & \(-\)0.015 & \(-\)1.254 & \(-\)1.140 \\ Average & 36.83 & 31.91 & 58.02 & 1.45 & \(-\)0.039 & \(-\)2.459 & \(-\)2.378 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Mechanical Parameters for Parallel Loading. strength of the slate samples in the yield deformation stage shows a similar variation, i.e., the greater the peak strength, the greater the expansion strength. The expansion strength of the cinerous samples is approximately 92.41% of that of gray samples. This indicates that the cinerous samples underwent dilation and rupture earlier in the yield deformation stage than the gray samples under vertical loading conditions, which is related to the physical properties of the diagenesis effect [24; 25]. The slate structures changed from a series relationship to a parallel relationship when the slate samples were subjected to parallel loading. The superimposed action of the slate strata caused the rock samples to exhibit a rock column effect [22; 25; 26]. The rock samples exhibited significant expansion deformation due to the tensile deformation of weak bedding surface, and the bearing capacity was significantly deteriorated compared with the vertical loading condition. A buckling failure occurred near the peak strength due to insufficient bearing capacity [27]. Table 2 shows that under parallel loading conditions, the peak strength of the gray samples at brittle fracture is 34.15-55.43 MPa with an average peak strength of 47.70 MPa, which is reduced by 18.24% compared with vertical loading. The peak strength of cinerous samples at brittle fracture is 13.98-54.88 MPa, and the average peak strength is 36.83 MPa, which is 31.70% lower than that for vertical loading. The expansion strength of slate samples also deteriorated significantly as shown in Tables 1 and 2, the expansion strength of the gray samples and the cinerous samples with yield deformation decreased by 25.87% and 27.44%, respectively, compared with the expansion strength under vertical loading conditions. It can be seen that the slate peak strength and expansion strength are consistently correlated with the slate structure, i.e., the greater the bearing strength, the greater the expansion strength of the slate sample in yield deformation.