## 7 Coal Burst Control and Verification of 76 Working Face in Wuyang Mine
### Numerical Simulation Verification of Drilling Pressure Relief Effect  
Based on the actual geological conditions of Wuyang Mine, a numerical model was established using the finite difference software FLAC\({}^{\mathrm{3D}}\) v9.0 to analyze the vertical stress on the isolated working face. The finite difference method (FDM) was used to solve the governing equations of stress and deformation in the rock mass. The dimensions of the model are: length = 995.0 m, width = 400.0 m, and height = 373.0 m, as shown in Figure 15.  
The model consists of 119,400 grid cells and 1,231,200 nodes. The upper boundary is defined as a stress boundary, where a vertical load is applied to simulate the weight of the overlying strata. The horizontal direction serves as a sliding and stress boundary. The sides of the model restrict horizontal movement, and the bottom restricts vertical movement. The simulation depth is 605.0 m. The post-mining space in the FLAC\({}^{\mathrm{3D}}\) simulation was modeled as a null model, representing fully excavated areas. The simulated post-mining space had a strike length of 200 m and a dip length of 295 m, consistent with the actual mining geometry. Based on the relationship between the actual burial depth of the coal seam and the height of the model, a vertical equivalent load of 13.5 MPa is applied to the upper surface of the model. The model adopts the Mohr-Coulomb constitutive model overall. After achieving in situ stress balance, the coal seam on both sides of the working face is excavated, followed by drilling and depressurization of the coal seam. The specific mechanical parameters, based on the drilling data from the 76 working face at Wuyang Mine and indoor rock mechanical strength tests, are shown in Table 6.  
The vertical stress distribution obtained from the FLAC\({}^{\text{3D}}\) simulation for the 76 working face is shown in Figure 16 with the corresponding vertical stress curve in Figure 17.  
Initially, the vertical stress on the working face increases, then decreases, and finally stabilizes from the coal wall to the coal seam depth. The stress concentration is mainly around 30 m on both sides of the working face, with the peak stress reaching 30.6 MPa. After implementing drilling pressure relief measures, the peak stress decreases and significantly shifts deeper into the working face, alleviating the stress concentration. These results are in close agreement with the previous theoretical analysis.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Rock Stratum** & \begin{tabular}{c} **Density** \\ **/kg\(\cdot\)m\({}^{-3}\)** \\ \end{tabular} & \begin{tabular}{c} **Bulk Modulus** \\ **/GPa** \\ \end{tabular} & \begin{tabular}{c} **Shear Modulus** \\ **/GPa** \\ \end{tabular} & \begin{tabular}{c} **Cohesion** \\ **/MPa** \\ \end{tabular} & \
\begin{tabular}{c} **Internal Friction** \\ **Angle (\({}^{\circ}\))** \\ \end{tabular} &
\begin{tabular}{c} **Tensile** \\ **Strength /MPa** \\ \end{tabular} \\ \hline Coal 3 & 1400 & 2.5 & 0.9 & 1.5 & 28 & 0.9 \\ Fine sandstone & 2460 & 5.6 & 4.4 & 2.9 & 35 & 1.8 \\ Sandy mudstone & 2000 & 3.1 & 1.8 & 1.6 & 32 & 1.5 \\ Coarse sandstone & 2530 & 7.3 & 5.2 & 4.1 & 32 & 3.3 \\ Silstone & 2450 & 4.8 & 3.4 & 1.9 & 32 & 1.3 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Mechanical parameters of coal and rock.  
Figure 16: The supporting stress cloud diagram before and after pressure relief of 76 working face: (**a**) Before pressure relief (Unit: Pa), (**b**) after pressure relief (Unit: Pa).  
Figure 15: Numerical simulation model.