# Study on Mechanism of Static Blasting-Induced Hard Rock Fracture Expansion
## 6 Conclusions  
This study conducted RSAC crack propagation experiments and PFC numerical simulations to investigate the principles and mechanisms of static blasting. It aimed to elucidate the characteristics of crack propagation in hard rock under static blasting and analyze the impact of different parameters on crack propagation. The following conclusions were drawn:  
1. From the perspective of hydration reaction, the study revealed the expansion mechanism and generation of expansion pressure by the fracturing agent. It also examined the mechanical aspects of fracturing hard rock caused by expansion pressure. The results showed a positive correlation between expansion pressure and aperture size. Additionally, the study provided a detailed description of the fracturing processes, including the micro-cracking stage, fissure development stage, and fracture stage in RSAC.
2. Using PFC2D software, a numerical model of dual-porosity specimens was established to simulate the expansion fracturing under confining pressure. The simulation revealed internal dynamic effects, microscopic particle motion laws, macroscopic fracture morphology, and crack propagation characteristics during the fracturing process. The study clarified the release of simulated expansion pressure resulting from changes in cracks within the dual-porosity specimens. Furthermore, it determined the magnitude of expansion pressure during complete penetration and rupture of specimens under different conditions.
3. The study analyzed the development trends of expansion fracturing in dual-porosity specimens considering various aperture sizes, spacing, and confining pressures. The findings indicated a positive correlation between aperture size and fracturing effect, while spacing and confining pressure exhibited a negative correlation. Moreover, the study revealed a negative correlation between aperture size and the magnitude of expansion pressure, while spacing and confining pressure presented a positive correlation.  
The research findings mentioned above significantly contribute to the development of environmentally friendly and efficient methods for fracturing hard rock in underground mining. These findings provide robust evidence regarding the effectiveness of static fracturing agents and introduce a novel approach for rapidly excavating hard rock in coal mines.  
Methodology, Y.C.; Software, S.H.; Formal analysis, L.T.; Writing--original draft, Z.X.; Writing--review & editing, C.L. All authors have read and agreed to the published version of the manuscript. This research was funded by National Natural Science Foundation of China (NSFC): 52374140.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
Data Availability Statement: All data, models, or codes that support the findings of this study are available from the corresponding author upon reasonable request.  
Conflicts of Interest: The authors declare that they have no known competing financial interest or personal relationships that could have appeared to influence the work reported in this paper.