## 3 Results and Discussion
### Influence of Gas Seepage on Outburst-Coal Breaking
Thereafter, free gas in pore-crack networks will obtain more kinetic energy for moving, wherein a great gas pressure gradient will be generated. From Equation (10), the seepage force scales linearly with gas pressure gradient as defined, indicating that elevated \(\partial p/\partial x\) means stronger seepage force applied to pore surface, which further intensifies coal fragmentation and pore-crack network propagation. Thus, a self-reinforcing cycle effect between gas seepage and coal fragmentation was established under these interactions when a coal and gas outburst occurred, where each process amplifies the others in cycle. This self-reinforcing cycle effect will play a significantly stimulative role in outburst initiation, and development and outburst could enhance this cycle's effect in turn. Finally, enhanced outburst process will further exacerbate excavation  
Figure 8: The self-reinforcing cycle effect of gas seepage on outburst-coal breaking. disturbance and stress unloading in turn, thereby restarting another self-reinforcing cycle. This finding of self-reinforcing cycle effect was supported in the recent studies [29; 31], in which permeability evolution during unloading was found to be non-monotonic and tied to microcrack coalescence, and it was also verified in the Multiphysics modeling studies [6]. As revealed by the experimental results in this study, different structural coal seams exhibited distinct levels of the cycle effect. Tectonic and soft coal seams exhibited stronger feedback gains compared to intact hard coal seams, driven by higher fracture density and smaller geo-forming stress. From Figure 8, we can find that the self-reinforcing cycle comprised two semi-cycle feedback mechanisms and one sub-cycle feedback. In the first semi-cycle, coal fragmentation during destabilization propagated the pore-fracture network, increasing permeability and accelerating gas seepage. The second semi-cycle predicated that enhanced gas pressure gradient elevated the gas seepage force applied on pore surface, exacerbating coal fragmentation, further increasing permeability, and accelerating gas seepage. And in the sub-cycle, gas seepage promoted faster desorption and diffusion. The resulting greater gas expansion energy elevated the pressure gradient, which indirectly raised permeability, finally accelerating gas seepage in turn. Without doubt, these interdependent sub-cycle mechanisms would synergistically enhance the self-reinforcing cycle's capacity to facilitate coal fragmentation and outburst escalation. The self-reinforcing cycle effect is a significant finding for in-depth understanding of the initial and developed mechanisms of coal and gas outburst. It could apply a theoretical mechanism basis for further research on methods of outburst prevention and early warning. In practice, prior to a coal and gas outburst, many precursory changes in stress state, coal structures, mining circumstance, and some key parameters will appear. Such as stress concentration, coal fragmentation, sudden temperature drop on workforce, sharp explosion sound, abnormal gas emission, and so on. Early warning of coal and gas outbursts can be achieved by real-time monitoring these precursor changes. The self-reinforcing cycle effect found in this study contains the key parameters of permeability, pore propagation extent, and gas emission amount. They can be quantitatively monitored in real-time through integration into an AI-driven big data monitoring system for proactive coal and gas outburst prevention and warning.