## 2 Engineering Background
### Monitoring System and Sensor Arrangement  
The KJ550 stress monitoring system is primarily used for real-time stress monitoring within mine roadways and working faces. Utilizing high-sensitivity sensor devices, it collects data on surrounding rock stress changes, providing data support for early warning of mining-induced earthquakes and other geological disasters. The stress sensors used in this study are primarily designed to measure changes in the stress environment of the roadway and surrounding rock mass. These sensors operate based on the strain gauge principle, detecting deformations caused by stress changes. When stress acts on the rock mass, the strain gauge deforms, resulting in measurable changes in electrical resistance. These resistance changes are recorded and used to analyze the magnitude of the stress and its variation over time. These sensors are highly sensitive and capable of providing real-time data, which is crucial for identifying stress concentration areas and potential risk zones, especially under deep mining conditions. Its advantages lie in high monitoring accuracy and rapid response speed, enabling dynamic stress monitoring and real-time monitoring of stress concentration areas, thus assisting in disaster prediction.  
The arrangement of stress sensors in roadways plays a crucial role in monitoring stress distribution and identifying potential risk areas. In this study, the sensors were deployed to ensure even distribution and effectively cover stress concentration areas, allowing for accurate measurement of stress variations over time. This approach ensures that the collected data represent the broad conditions of the roadway and surrounding areas, which is essential for mine-induced earthquake prediction analysis. Furthermore, cost is an important consideration when deploying these sensors. While the cost of sensors is relatively low compared to other mining equipment, their number and placement are optimized to enhance data accuracy while avoiding unnecessary expenses. Therefore, the monitoring scheme not only ensures data precision and broad coverage but also takes budget constraints into account. Figure 3 shows the arrangement of KJ550 stress sensors in the 3308 working face.  
The SOS microseismic monitoring system, developed by the Polish Mining Research Institute, is widely applied in underground mining environments such as coal mines due to its high sensitivity and real-time data acquisition capabilities, meeting the demands of complex, high-stress mining areas. The SOS microseismic monitoring system used in the Yangcheng Coal Mine employs velocity-type sensors with a sampling frequency of 500 Hz. Through microseismic sensors positioned at various locations, it can accurately capture microseismic signals during coal and rock fracturing processes. Using algorithms such as the L1/L2 norm simplex and Newton iterative methods, the system performs source localization and energy calculations for microseismic events. This enables effective  
Figure 3: Online arrangement of KJ550 stress sensors at the 3308 working face.  
monitoring and early warning of coal and rock dynamic hazards (e.g., rockburst) and provides reliable support for predicting the development trends of dynamic phenomena like mining-induced earthquakes. Figure 4 illustrates the arrangement of effective microseismic sensors near the 3308 working face.