# Study on the Law of Mine Pressure Manifestation in Three-Soft Coal Seam Isolated Working Face
## 5 Simulation Study of Mine Pressure Law in Gudao Working Face
### Evolution Analysis of Plastic Zone of Roadway Surrounding Rock During Mining  
The evolution process of the plastic zone is directly related to the long-term stability and safety of the roadway. With the advance of the working surface, the stress of the surrounding rock is constantly adjusted, and the plastic zone gradually expands and redistributes. In-depth analysis of the evolution law of the plastic zone of the surrounding rock of the roadway not only helps to reveal the instability mechanism of the surrounding rock but also provides an important basis for reasonable support design and mine pressure control. The variation range of the plastic zone under different advancing distances is shown in Table 4.  
Figure 12 illustrates the evolution of the plastic zone in the roof of the isolated working face at different advancing distances. During the advancement process, the roof strata are significantly affected by shear and tensile forces, leading to the formation and expansion of the plastic zone. This evolution is closely related to the progression of the working face, gradually altering the structure and mechanical properties of the roof. As the isolated working face begins to advance, the roof strata, under the combined influence of the support system and their own weight, gradually transform into a cantilever beam structure. With continued advancement, the cantilever beam undergoes a periodic process of \"stability-instability-restabilization,\" which is characterized by the formation of \"O-X\" fracture patterns along the advancing direction. Specifically, during the initial advancement stage \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Advance Distance (m)** & **Evolution Law of Plastic Region** & **Fracture Pattern** & **Change Trend and Analysis** \\ \hline \multirow{4}{*}{40–120 m} & The plastic zone of the roof continues to expand, and the shear and tensile failure are significant & \"O-X” type fracture & The “O-X” type structure formed after the roof is broken gradually increases, the force concentration effect is significant, and the damage risk is high. Special attention should be paid to the effectiveness of supporting measures and the strategies to prevent the roof instability. \\ \hline \multirow{4}{*}{120–160 m} & The plastic zone continues to expand, the damage gradually increases, and the structure continues to be in an unstable state & “O-X” type fracture & The risk persists as the plastic zone expands and causes stress redistribution and larger-scale breakage. \\ \cline{2-4}  & The plastic zone begins to shrink, the roof structure tends to be stable, and the risk of failure is reduced & “O-X” type fracture & The plastic zone of the roof is reduced to form a more stable bearing mode, the periodic failure is gradually reduced, and the roof is adjusted to a more stable state after long-term promotion and failure. \\ \hline \hline \end{tabular}
\end{table} 
Table 4: The variation in plastic zone at different advancing distances. (from 40 m to 120 m), the shear and tensile failures of the roof lead to the continuous expansion of the plastic zone. After each roof fracture, the scale of the \"O-X\" fracture structure becomes progressively larger than before. The stress concentration effect on the roof strata becomes increasingly pronounced, and with every additional distance advanced, the redistribution of stress and changes in the extent of the plastic zone trigger new, larger-scale fractures. When the isolated working face advances to 160 m and beyond, the evolution of the plastic zone in the roof exhibits a new trend. The \"O-X\" fracture structure formed in the roof no longer increases in size as it did previously but instead begins to shrink. This change may be attributed to mechanical adjustments in the strata caused by prolonged advancement and repeated fracturing. During the process of plastic deformation and periodic failure, the roof gradually develops a more stable load-bearing mode.