## 2 Identification of Mechanical Parameters of Rock Samples in Static Tests
### Porosity Measurements  
In the tomographic assessment, both visual evaluation and the results of porosity analysis were considered. In the visual assessment, a varied quantity of pores was observed \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**No**} & \multirow{2}{*}{**Name**} & **Volumetric** & **Compressive** & **Tensile** & **Young** & **Young** & **Porosity, \%** & **Energy** \\  & & **Density** & **Strength** & **Strength** & **Modulus** & **Modulus** & **CoV\({}_{\text{EA}}\), \%** & **(CV\({}_{\text{WA}}\)), \%** \\ \hline
1. & Apricot & 0.73 & 14.65 & 21.68 & 19.21 & 18.23 & 1.03 & 12.21 \\ \hline
2. & Barwald & 0.37 & 26.46 & 24.58 & 17.91 & 15.01 & 14.49 & 21.08 \\ \hline
3. & Kandla & 0.29 & 11.93 & 25.33 & 16.62 & 16.12 & 25.53 & 17.58 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Summary of the coefficient of variation of physico-mechanical parameters determined for the tested samples. Figure 5: Results of volumetric density testing (**a**), UCS and BTS testing (**b**,**c**), the modulus of elasticity (Tangent Young’s modulus) testing (**d**). in three sandstone groups. The most porous structure was evident in Apricot Pink samples, where these pores were significantly larger than in other cores while maintaining a substantial pore quantity. The pore structure tended to form channels, and these interconnected pores created voids with a volume of up to 3.5 mm\({}^{3}\) (Figure 6). These voids are visible in 3D visualization by adjusting color to the scale corresponding to a larger pore volume. Upon analyzing Barwald samples, a significant reduction in pores was noted (Figure 7). The tendency for pores to connect remained limited, but interconnected clusters of pores were still visible. These connections took the form of elongated voids with a volume not exceeding 0.16 mm\({}^{3}\). The situation for Kandla Grey samples was different (Figure 8). Pores had a volume of no more than 0.01 mm\({}^{3}\) and did not exhibit a tendency to group together. The porosity of Kandla Grey was notably lower. In the tomographic cross-sections, air pores are represented in black. Another visible feature is the inclusions on cross-sectional drawings, appearing as bright spots. Inclusions naturally occur in sandstone and involve the presence of denser inclusions. Apricot Pink, in this regard, exhibits notably fewer inclusions. Figure 6: Results of tomographic imaging for Apricot Pink sandstone (UCS = 126.7 MPa, porosity = 8.32%): (**a**) vertical cross-section of core A; (**b**) 3D view with an analysis of core A’s porosity; (**c**) vertical cross-section of core B; (**d**) 3D view with an analysis of core B’s porosity; (**e**) vertical cross-section of core C; (**f**) 3D view with an analysis of core C’s porosity. Figure 7: Results of tomographic imaging for Barwald sandstone (UCS = 78.8 MPa, porosity = 0.65 %): (**a**) vertical cross-section of core A; (**b**) 3D view with an analysis of core A’s porosity; (**c**) vertical cross-section of core B; (**d**) 3D view with an analysis of core B’s porosity; (**e**) vertical cross-section of core C; (**f**) 3D view with an analysis of core C’s porosity. On the charts in Figure 9, the relationship between the number of pores and their size is presented in an averaged manner for the sample group. Due to the scale of the chart, the largest pores were omitted. In the case of Apricot Pink samples, an average total of 381,846 pores was determined, with 386,604 for Barwald, and 20,072 for Kandla Grey. An average total of 381,846 pores was determined for Apricot Pink samples, with 386,604 for Barwald, and 20,072 for Kandla Grey. The charts demonstrate a significant variation in the occurrence of pores of specific sizes.