## 2 Experimental Work  
### Sample Collection and Preparation  
The granite specimens used in this test were cut from natural stones by a cutting machine and then processed by a sander to make their edges smooth enough to meet the mechanical test specifications for such rocks. In order to reduce the dispersion of the experimental results caused by individual differences in rock specimens and improve the comparability of the test, the granite samples were all taken from one intact rock mass, so the lithologic parameters of the samples can be considered to be approximately the same.  
Based on the recommendations of the International Society of Rock Mechanics, the main mechanical parameters in Table 1 were obtained by the uniaxial compression test, Brazilian tensile test, and shear test.  
According to previous research [27; 28; 29], when the ratio of the depth of the plastic zone to the width of the sample is less than \(1/6\), the size effect can be ignored. Therefore, according to the cavity expansion model [30], the relevant parameters are expressed by the following equations:  
\[(1+\mu)\xi^{(1+K_{d})/K_{d}}-\mu_{\xi}^{(K_{p}-1)/K_{p}}=\gamma \tag{1}\]  
\[K_{d}=\frac{1+\sin\phi}{1-\sin\phi};K_{p}=\frac{1+\sin\psi}{1-\sin\psi} \tag{2}\]  
\[\mu=\frac{\lambda K_{p}}{K_{d}+K_{p}} \tag{3}\]  
\[\lambda=\frac{\left(K_{p}-1\right)(K_{d}-1)+(1-2v)\left(K_{p}+1\right)(K_{d}+ 1)}{2K_{p}} \tag{4}\]  
\[\xi=\frac{r_{*}}{t} \tag{5}\]  
where \(\gamma\) is a characteristic parameter for the shape of the disc cutter, for the blunt cutter used in this test \(\gamma=0\), \(r_{*}\) is the critical radius of the plastic zone, \(t\) is the penetration depth, and \(\phi\) and \(\psi\) are the rock friction angle and dilatancy angle, respectively, the dilatancy angle is equal to the friction angle in this test.  
Based on the analysis above, the samples used in this test were tabular specimens with a size of 250 mm \(\times\) 200 mm \(\times\) 100 mm (length \(\times\) height \(\times\) width). By substituting the rock mechanics parameters in Equation (1) into Equation (5), it has been determined that the ratio of the radius of the plastic deformation zone to the minimum size of the specimen is far less than \(1/6\). So, the rock sample size is reasonable.  
All the samples were placed in an oven at 115 \({}^{\circ}\)C, and the mass was weighed at predetermined intervals until the mass reduced to a constant value. At that time, the sample was considered to be in a \"completely\" dry state. Then, the dry samples were immersed in pure water for different times to achieve different water contents. Figure 1 shows the water content of the specimens during the saturation processes. It can be seen that a dry granite specimen reached its saturated state after about 24 h, and the maximum water content of the specimen could be 0.43%. Therefore, five sets of water content levels (i.e., 0, 0.11, 0.22, 0.32, and 0.43%) were designed for the tests. The water absorption of a rock specimen could be calculated by the weight variation:  
\[w_{w}=\frac{m_{w}-m_{d}}{m_{d}}\times 100\% \tag{6}\]  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Density** & **Water** & **Compressive** & **Tensile** & **Elastic** & **Friction** & **Poisson** \\
**(g\(\cdot\)cm\({}^{-3}\))** & **Content (\%)** & **Strength (MPa)** & **Strength (MPa)** & **Modulus (GPa)** & **Angle (\({}^{\circ}\))** & **Ratio** \\ \hline  & 0 & 105.1 & 8.4 & 20.1 & 49.5 & 0.21 \\  & 0.11 & 96.6 & 7.6 & 18.5 & 45.2 & 0.23 \\
2.97 & 0.22 & 92.9 & 6.9 & 17.7 & 41.1 & 0.26 \\  & 0.32 & 81.9 & 6.0 & 15.7 & 38.2 & 0.24 \\  & 0.43 & 76.1 & 5.1 & 14.5 & 35.6 where \(w_{w}\) (%) is the water content of the specimen and \(m_{w}\) (g) and \(m_{d}\) (g) are the wet and dry masses of the specimen, respectively.