## 2 Analysis of Rockburst Manifestation Characteristics
### Analysis of Rockburst Manifestation in Roadway Surrounding Rock
#### 4.2.3 Plastic Zone Evolution Characteristics  
To further examine plastic failure behavior, the plastic zone development in the xy-plane under different schemes was compared. Figure 10 displays the outcomes.  
Figure 10: Evolution of plastic zones in the xy-plane under different hydraulic fracturing schemes: (**a**) No pressure relief; (**b**) Scheme 1; (**c**) Scheme 2; (**d**) Scheme 3; (**e**) Scheme 4; (**f**) Scheme 5; (**g**) Scheme 6; (**h**) Scheme 7; (**i**) Scheme 8; (**j**) Scheme 9.  
As shown in Figure 10a, without any pressure relief measures, the plastic failure areas on the roadway's two sides are mainly distributed approximately 1.5 m to 2.0 m from the sidewalls, where initial shear failure of the surrounding rock has occurred. This indicates that under the influence of mining-induced stress, local regions have entered an intense plastic stage, showing a clear tendency toward instability. At this stage, internal stresses in the surrounding rock remain unreleased, which may lead to energy accumulation and further roadway damage.  
From Figure 10b-j, it is evident that after implementing hydraulic fracturing pressure relief measures, the extent and distribution of plastic zones in the surrounding rock change significantly, displaying varying degrees of expansion and evolution.  
In Scheme 1, the plastic zone extended to a range of 3.5-5.5 m. Although the extent of failure increased, the distribution was uneven and the degree of fracture development remained weak. Scheme 2 exhibits further expansion of the plastic zone to 5.5-6.5 m, with improved fracture connectivity indicating enhanced pressure relief effectiveness. Schemes 3 and 4 both display plastic zones extending from 2.0 to 10.0 m, characterized by relatively continuous failure regions. This suggests that the hydraulic fractures had formed well-connected channels within the roof structure, thereby facilitating efficient stress release. In Scheme 5, the plastic failure zone was concentrated within the 2.5-8.5 m range, with a deeper concentration of damage likely due to an unfavorable fracture propagation direction that limited lateral pressure relief. Scheme 6 demonstrates the smallest plastic zone, confined to 4.0-4.5 m, indicating that fracture development paths were restricted and effective pressure relief channels could not be formed. Scheme 7 shows a plastic zone between 2.5 and 10.0 m, with a relatively balanced distribution. Scheme 8 produces the widest plastic zone, reaching 4.0-12.0 m. However, regions of intense failure were observed, raising concerns regarding potential structural instability. In contrast, Scheme 9 results in a concentrated plastic zone within the 8.5-12.5 m range, without the emergence of new high-intensity failure areas. This indicates that the fracture network had fully developed, stress had been adequately released, and the surrounding rock had reached a relatively stable state. These results suggest that Scheme 9 offers the most favorable plastic zone evolution, achieving effective stress dissipation while avoiding widespread plastic damage to the surrounding rock, thus providing strong pressure relief protection for both sides of the roadway.