## 3 Results
### 3.3. Seepage Behaviour of SLA Samples
#### 3.3.2 Rocks with Coarse Pores  
Porous basalt with coarse pores has a high potential for CO\({}_{2}\) geological storage. This section investigates the feasibility of the SLA method to reconstruct the pore structures and to investigate the permeability of the porous basalt originating from Wudalianchi City in northeastern China. The CT scanning found that the diameter of most pores inside the rock is higher than 0.3 mm, which is suitable for the SLA method to replicate the pores.  
The SLA samples are cubic, measuring 30 mm \(\times\) 30 mm \(\times\) 30 mm. The porosities of all the samples were measured before seepage tests, as shown in Table 4. The porosities are relatively stable, reflecting the SLA technique's advantage in making parallel samples. They are slightly lower (about 7%) than the original rock, probably attributing the incapability of the print machine to the small pores. It is worth noting that the porosity measured by the vacuum pumping method in this paper is open porosity, which includes the ratio of the volume of interconnected pores to the sample volume. The sintering temperature is 70 \({}^{\circ}\)C to prevent the deterioration of the binder materials in 3 DP samples.  
Seepage tests were performed on 3 DP samples to determine their permeability. Three groups of specimens were tested, with each group consisting of three parallel specimens oriented along three seepage directions perpendicular to the cubic surfaces (designated as Faces A, B, and C in Figure 7), in order to investigate the anisotropy of the permeability. Due to the use of epoxy resin to fix and seal the other four surfaces, each specimen could only be tested in a single seepage test, and reuse was not possible. Consequently, the original rock sample was only tested along the seepage direction perpendicular to Face A. To ensure test reliability, three parallel tests were conducted for each seepage direction, and the average value was used to calculate the final permeability coefficient for that direction.  
\begin{table}
\begin{tabular}{c c c c c c} \hline
**Specimen** & **Porosity** & **Average** & **Seepage Face** & **K** & **Average K** \\
**No.** & **(\%)** & **Porosity (\%)** & **Seepage** & **(10\({}^{-4}\) cm/s)** & **(10\({}^{-4}\) cm/s)** \\ \hline Origin & 25.41 & 25.41 & A & 3.13 & 3.13 \\ \hline
1 & 22.97 & & & 2.74 & \\
2 & 27.78 & 24.90 & A & 2.91 & 2.77 \\
3 & 23.96 & & & 2.66 & \\ \hline
4 & 23.85 & & & 5.34 & \\
5 & 22.30 & 23.10 & B & 5.13 & 5.11 \\
6 & 23.14 & & & 4.87 & \\ \hline
7 & 23.86 & & & 9.85 & \\
8 & 22.73 & 23.24 & C & 10.75 & 10.28 \\
9 & 23.12 & & & 10.23 & \\ \hline \end{tabular}
\end{table}
Table 4: Porosities and permeability coefficients K of the natural basalt and its 3 DP replications.  
Table 4 presents the permeability coefficients of the original rock sample and the 3 DP replication samples. The permeability coefficients perpendicular to Face A for both the original rock and the replicated samples are very similar, differing by only approximately 10%. This result suggests that SLA 3 DP samples can be used to represent the permeability of coarse porous rocks accurately. However, the permeability coefficients differ significantly along the three flow directions, indicating the anisotropy of permeability. Despite the similarity in pore structure among specimens exposed to different surfaces, significant differences in permeability perpendicular to these surfaces were observed. Notably, the maximum permeability coefficient (perpendicular to Face C) was over three times higher than the minimum value (perpendicular to Face A).