## 2 Experimental Setup and Procedure
### Testing Procedure  
As shown in Figure 4, three different forms of mining-induced disturbance load application schemes are designed. The vertical direction is the maximum principal stress used to apply static, cyclic, and transient loads. The horizontal X-axis direction is the intermediate principal stress, while the horizontal Y-axis direction is the minimum principal stress. The unloading is realized through the forced drop bar to simulate the free surface in the mining process.  
Table 1 shows the mining disturbance load experimental scheme with different influence factors. The control variables of static loads include different disturbance stress growth rates: 0.1, 0.2, 0.3, 0.4, 0.5 MPa/s, and different initial stress levels: 10, 12, 14, 16, 18 MPa. The control variables for cyclic loads include different cyclic amplitudes: 2, 4, 6, 8, 10 MPa, and different cyclic frequencies: 0.2, 0.4, 0.6, 0.8, 1 Hz. The control variables for transient loads include different transient increments: 1, 2, 3, 4, 5 MPa, and different initial stress levels: 10, 12, 14, 16, 18 MPa.  
The entire mining stress path under different mining-induced disturbance loads is shown in Figure 5. The disturbance process of each type of load was divided into six stages namely:  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Load Types** & **Testing Group** & **Control Variables** & **Variables Range** \\ \hline \multirow{2}{*}{Static load} & S-V & Disturbance rate & 0.1, 0.2, 0.3, 0.4, 0.5 MPa/s \\  & S-L & Stress level & 10, 12, 14, 16, 18 MPa \\ \multirow{2}{*}{Cyclic load} & C-A & Cyclic amplitude & 2, 4, 6, 8, 10 MPa \\  & C-F & Cyclic frequency & 0.2, 0.4, 0.6, 0.8, 1.0 Hz \\ \multirow{2}{*}{Transient load} & T-I & Transient increment & 1, 2, 3, 4, 5 MPa \\  & T-L & Stress level & 10, 12, 14, 16, 18 MPa \\ \hline \hline \end{tabular}
\end{table}
Table 1: Different types of coal samples and their numbers.  
Figure 4: Different types of load disturbance.  
Figure 3: Coal burst characteristics.  
(1) Initial load stage I: the loads were first increased to the equivalent initial stress environment at a rate of 0.05 MPa/s, \(\sigma_{1}\) = 8 MPa, \(\sigma_{2}\) = 6 MPa, \(\sigma_{3}\) = 4 MPa.  
(2) Initial load holding stage II: the loads in the three directions were kept constant for the 30 s.  
(3) Roadway excavation stage III: the \(\sigma_{3}\) direction side is unloaded instantaneously to simulate the actual situation of sudden unloading of stress on one side of the coal body during roadway excavation. While \(\sigma_{1}\) and \(\sigma_{2}\) were kept constant for the 30 s.  
(4) Working face mining stage IV: \(\sigma_{2}\) was slowly unloaded to 4 MPa at a disturbance rate of 0.1 MPa/s, \(\sigma_{1}\) was loaded to different stress levels (10, 12, 14, 16, 18 MPa) at a disturbance rate of 0.2 MPa/s to simulate the actual situation of radial unloading and axial loading during working face mining period.  
(5) Load holding stage V: the loads in the three directions were kept constant for the 30 s.  
(6) Mining disturbance stage VI: \(\sigma_{1}\) was loaded at different static load disturbance rates (0.1, 0.2, 0.3, 0.4, 0.5 MPa/s), different cyclic perturbation amplitudes (2, 4, 6, 8, 10 MPa), different cyclic perturbation frequencies (0.2, 0.4, 0.6, 0.8, 1.0 Hz), different transient increments (1, 2, 3, 4 5 MPa) while \(\sigma_{2}\) was kept constant until the coal sample is destroyed, and the experiment ends.