## 4 Influence of Advance Rate on Front Abtment Pressure
### Field Monitoring of Microseismic Event Distribution in the 12308 Working Face  
During the advancing process of Panel 12308, the KJ768 microseismic monitoring system was deployed to monitor and warn against rockburst hazards. When internal stresses exceed local strength limits in rock masses during mining or geological activities, microscopic fracturing (e.g., crack propagation, grain boundary slip) occurs, releasing elastic strain energy. This energy propagates as elastic waves (P-waves and S-waves), forming microseismic events. The KJ768 system detects these elastic wave signals to invert fracture locations, energy magnitudes, and rock mass damage levels. The layout of microseismic monitoring points is shown in Figure 19. The system configuration includes two microseismic monitoring substations, eight geophones, and ancillary equipment. One substation was installed in the power supply chamber of the 12308 belt entry and the other at the entrance of the 12308 return airway. Sensor groups were arranged as follows: Starting 150 m outward from the open-off cut along the belt entry and return airway, the first group of monitoring points was deployed. Four sensor groups were installed in the belt entry (on the non-mining side), with a spacing of 150 m between each group. Similarly, four sensor groups were installed in the return airway (on the mining side), also spaced 150 m apart. As the working face advanced to approximately 40 m ahead of the first sensor group, additional sensor groups were added in both entries. Data signals were transmitted from underground substations to the surface ground pressure monitoring room, enabling 24 h continuous monitoring. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Stage** & **Support Position** & **Weighting Frequency** & **Periodic Weighting Interval(m)** & **Support Load During Weighting(/kN)** & **Remarks** \\ \hline Low-speed & Upper & 13 & 10.2 & 14,091.6 \\  & Middle & 12 & 10.3 & 14,454.6 \\  & Lower & 12 & 10.5 & 14,133.9 \\  & & 12.3 & 10.3 & 14,226.7 \\  & Upper & 9 & 15.4 & 14,235.7 \\ High-speed & Middle & 8 & 15.5 & 14,529.4 \\ mining phase & Lower & 9 & 14.4 & 14,231.4 \\  & & 8.7 & 15.1 & 14,332.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Summary of relationships between working face advance rates and periodic weighting characteristics. Figure 19: Layout of microseismic monitoring points. Microseismic events during mining were classified using maximum energy (E\({}_{\max}\)) and peak frequency as critical thresholds to distinguish between rockburst-free and rockburst-prone conditions. The microseismic early-warning classification is detailed in Table 7.  
Integrated with actual field production activities, the correlation diagrams between the daily face advancing rate, daily microseismic event frequency, and daily total microseismic energy at Panel 12308 are presented in Figures 20 and 21, categorizing microseismic behaviors into low-speed and high-speed advancing phases. Analysis of the data presented in Figures 20 and 21 reveals the following outcomes: During the low-speed advancing phase, a total of 82 microseismic events were recorded, averaging 1.4 events per day, while the high-speed advancing phase exhibited 502 microseismic events, averaging 3.4 events per day. The cumulative energy of microseismic events during the low-speed phase measured 5.46 \(\times\) 10\({}^{5}\) J, with a daily average energy of 9.4 \(\times\) 10\({}^{3}\) J, whereas the high-speed phase demonstrated a significantly higher cumulative energy of 3.33 \(\times\) 10\({}^{6}\) J and a daily average energy of 2.2 \(\times\) 10\({}^{4}\) J. Comparative characteristics of microseismic event distribution patterns across different advancing phases are systematically summarized in Table 8.