## 2 Similarity Simulation Experiment Design
### Experiment Data and Methods  
After the model is established and each monitoring system is prepared, the test stage of the model test is formally entered, including simulation of initial in situ stress field, installation and commissioning of the monitoring system, excavation of roadway, phased excavation of stope face, and loading impact dynamic load, etc. The specific process is as follows:  
1. Start the electric control loading system and control the hydraulic cylinder to apply a uniform load on the top of the model to simulate the initial ground stress field;
2. Connect the pressure sensor connection line with the static resistance strain gauge acquisition channel one by one according to the number in the layout scheme, calibrate and zero the reading of the pressure test system, and start recording. A total of 40 pressure sensors are installed;
3. According to the layout plan, the four acceleration sensors are arranged in the designated positions respectively, and the acceleration sensors relate to the vibration signal acquisition instrument. After the quasi-static excavation is completed, the recording starts before the impact dynamic load is applied;
4. Adjust the optimal position of the dynamic high-speed camera system, and start recording before the impact dynamic load is applied;
5. Excavation roadway, section size of 80 mm \(\times\) 60 mm (height \(\times\) length). Then, the stope face is excavated step by step, with a total length of 900 mm. For the excavation  
Figure 1: Structure size of similar model test.  
method of driving in the opposite direction and stopping face, the driving face is first excavated, and then the stopping face is excavated after standing for 8 h. Each cycle of excavation is 5 cm, representing the actual advancing distance of the stopping face is 5 m. A total of 18 cycles of excavation are completed. At the same time, the internal pressure, surface displacement, and roadway deformation and failure characteristics of the model were observed;
6. After the mining face excavation is in place, the electric control system controls the pendulum falling freely from different heights to simulate the impact dynamic load. At the same time, the internal pressure, surface displacement, roadway deformation and failure characteristics, acceleration, and velocity of the model are observed and recorded until the surrounding rock of the roadway is destroyed, and the test is finished.  
By adjusting the pendulum falling from different heights to simulate the impact dynamic load of different strengths, according to the design data of the platform, the weight of the pendulum is 20 kg, the length of the pendulum is 1.0 m, and the maximum height that the pendulum can be lifted is 2.0 m. Therefore, the maximum gravitational potential energy that can be input is, and according to the energy similarity ratio of \(1.67\times 10^{4}\), the maximum potential energy that can be simulated in practice is about 6.55 \(\times\) 10\({}^{6}\) J, which is roughly equivalent to the value of the maximum mine shock energy generated by the rock burst during on-site production. Therefore, the impact dynamic load can effectively simulate the external mine shock disturbance in the process of coal mine production. Pendulum height and simulated energy are shown in Table 2.