## 5 Blasting Scheme Design and Effect Evaluation
### Evaluation of the Pressure Relief Effect of Long-Distance Drilling Blasting  
Since mining of the 2412 working face began in April 2023, the process has been divided into two stages according to the pressure relief methods in different areas. The first stage was the roof deep hole blasting mining stage, and the second stage was the long-distance drilling blasting mining stage. Micro seismic activity reflects the characteristics of micro seismic activity in a certain period of time in a certain area. A distribution cloud diagram of micro seismic activity before and after pressure relief of long-distance drilling blasting was selected for analysis to evaluate the pressure relief effect of long-distance drilling blasting. The time span of each stage was two months, allowing us to evaluate the pressure relief effect of long-distance drilling blasting.  
According to Figure 12, during the mining period of the working face, the micro seismic activity in front of the mining area was high, and the micro seismic energy in front of the mining area was relatively concentrated. By comparing the micro seismic activity cloud maps of the three stages of long-distance drilling blasting and roof deep hole blasting before and after the implementation of long-distance drilling blasting, it can be seen that in the initial roof deep hole blasting stage, the micro seismic activity index in front of the mining area reached 0.5. After the implementation of long-distance drilling blasting pressure relief, the activity was significantly reduced, indicating that after long-distance drilling blasting, the energy had been released in time to reduce the rock burst danger caused by the accumulation of a large amount of energy in the roof strata.  
Figure 11: Drilling Construction Drawing.  
Figure 10: Schematic diagram of long-distance drilling and blasting area.  
Finally, according to the measured micro seismic data, a comparison diagram of energy and frequency changes of micro seismic events before and after long-distance drilling blasting was drawn, as shown in Figure 13.  
According to Figure 13, after the implementation of long-distance drilling blasting, the frequency and energy of micro seismic events showed a significant downward trend. The daily average energy was reduced from 370 J to 250 J. The energy of events with micro seismic energy between 1.0 \(\times\) 10\({}^{2}\) J and 1.0 \(\times\) 10\({}^{4}\) J was greatly reduced after the implementation of long-distance drilling blasting pressure relief. The frequency of micro seismic events with energy between 1.0 \(\times\) 10\({}^{3}\) J and 1.0 \(\times\) 10\({}^{4}\) J was reduced by 61.7% after the implementation of long-distance drilling blasting pressure relief, and there was no event with micro seismic energy greater than 104 J, indicating that long-distance drilling blasting effectively reduces the accumulation of large energy events. The energy was released in time to minimize the risk of rock bursts caused by sudden releases.  
Figure 12: Cloud map of activity distribution in the working face.  
Figure 13: Micro seismic changes in long-distance drilling and blasting during construction. (**a**) Energy. (**b**) Frequency.  
According to the measured data of the roof displacement of the two entries in the working face before and after the implementation of long-distance drilling blasting, the average values of the roof surface displacement in the three stages were compared, and the displacement changes were drawn, as shown in Figure 14. According to the figure, after the implementation of long-distance drilling and blasting, the displacement of the roof surface of the return airway and the transportation entry was reduced by 15 mm before the measures were taken, indicating that long-distance drilling and blasting effectively reduced the deformation of the entry and avoided the entry itself. The roof caused a greater degree of damage and ensured the safe mining of the working face.