## 5 The \"Overall-Local\" Coal Burst Prevention and Control Strategy of Isolated Working Face  
### Local Coal Burst Prevention and Control Strategy  
Through the analysis of rock mechanics and mine pressure theory, it is concluded that the primary reason for the overall stability and local instability of the isolated working face is its relative width and sufficient bearing strength. The stress transferred from the goat on both sides to the working face is substantial, resulting in local conditions where \(\sigma_{x}\) > R\({}_{x}\)  
\begin{table}
\begin{tabular}{c c c} \hline
**Local Stability (B)** & **Stable (A\({}_{1}\))** & **Unstable (A\({}_{2}\))** \\ \hline
**Stable (B\({}_{1}\))** & Stable (A\({}_{1}\) + B\({}_{1}\)) & Overall coal burst (A\({}_{2}\) + B\({}_{1}\)) \\ \hline
**Unstable (B\({}_{2}\))** & Local coal burst (A\({}_{1}\) + B\({}_{2}\)) & Coal burst (A\({}_{2}\) + B\({}_{2}\)) \\ \hline \end{tabular}
\end{table}
Table 3: “Overall-local” coal burst types of isolated working face.  
while the overall working face maintains \(\sigma<R\), thus forming an overall stable working face with local instability.  
For coal burst types primarily involving localized coal bursts, pressure relief measures are usually taken on the coal [32]. Common pressure relief methods include drilling pressure relief and hydraulic fracturing. In addition to drilling pressure relief and hydraulic fracturing, other methods such as destress blasting have also been considered and, in certain cases, used to prevent coal bursts in coal seams. Destress blasting creates controlled fractures within the coal seam to release accumulated stress, thereby preventing sudden stress release that could trigger coal bursts. Typically, destress blasting is used in combination with drilling to enhance the effectiveness of coal burst prevention in high-stress areas. However, in the case discussed in this study, destress drilling was the primary method used, mainly due to the specific geological conditions and operational considerations of the mine. The decision to focus on drilling pressure relief was based on local experience and the demonstrated effectiveness of this method in similar conditions.  
Taking drilling pressure relief as an example, as shown in Figure 10, the diagram shows the following parameters: \(L_{b}\) is the drilling depth (m), \(R_{b}\) is the drilling diameter (mm), \(d_{b}\) is the drilling spacing (m), \(D_{x}\) is the distance between the drilling and the working face (m), \(d_{x}\) is the distance between the drilling and the bottom plate (m), and \(k\)' is the risk correction coefficient of the pressure relief drilling spacing, which is related to the drilling powder discharge. \(d\) is the diameter of the drill bit for pressure relief drilling construction (mm), \(K\) is the deformation modulus index, \(K=\lambda/E\); \(\lambda\) is the post-peak softening modulus of the stress-strain curve; \(E\) is the elastic modulus before the peak of the stress-strain curve (MPa).  
Drilling pressure relief induces controlled structural damage to the coal, transferring high stress from the edge of the coal to the deeper regions of the isolated working face [33] thereby achieving localized pressure relief. Specifically, a larger drilling diameter results in a larger pressure relief zone and a more pronounced pressure relief effect; smaller drilling spacing facilitates the formation of penetrating cracks between the holes, enhancing the pressure relief effect; deeper drilling depth allows higher stress near the roadway to be transferred to a deeper location [34]. The main parameters for drilling pressure relief are shown in Table 4 [35; 36].  
Figure 10: Drilling pressure relief diagram.