## 4 Results and Discussion
### Influence of Different Parameters on the Deformation of Surrounding Rock  
(1) Shallow borehole diameter  
From Figure 7, it can be seen that when there is without pressure relief borehole in the roadway, the maximum deformation of the two sides is 287.5 mm, and the maximum deformation of the roof is 330.7 mm. The shallow borehole diameter and the deformation of the two sides show a positive correlation, and the roof and floor convergence is also positively correlated.  
When the diameter of shallow boreholes is between 0 and 120 mm, the displacement of two side coal walls is slightly reduced, mainly because the boreholes provide deformation space for two sides of the surrounding rock. After the diameter of shallow boreholes is larger than 120 mm, the deformation of roadway sides begins to increase, and the growth rate increases with the increase in diameter of shallow boreholes. The deformation of the roof-to-floor convergence of the roadway increases with the increase in the diameter of the shallow borehole, and the rate of increase is unchanged.  
Figure 6: The vertical stress distribution curve of surrounding rock under different borehole spacing: (**a**) vertical stress, (**b**) stress peak and location, and (**i**-**vi**) vertical stress simulation cloud diagram.  
Figure 7: The curve of roadway deformation under different shallow borehole diameters: (**i**–**v**) horizontal displacement.  
(2) Deep borehole Diameter  
As can be seen from Figure 8, the connection between the change of the deep borehole diameter and the surface deformation of the roadway surrounding rock is weaker; although it shows a positive correlation, the increase is small. From this, it can be seen that the influence of deep borehole diameter on the roadway surface deformation is small, mainly because the location of the variable borehole diameter is outside the anchorage zone of the roadway, and the diameter of the boreholes in the anchorage zone is small, which has a small influence on the weakening of the strength of the surrounding rock. It also explains that the main factor affecting the surface deformation of the roadway is the boreholes in the anchorage zone.  
(3) Variable aperture position  
As shown in Figure 9, the deformation of roadway sides is reduced by 103.6 mm, 168.6 mm, 174.7 mm, 184.2 mm, and 191.0 mm, respectively, when compared with the position of variable borehole is 0 m. When the position of the variable borehole is in the anchorage area, the influence on the deformation of the roadway is larger. Therefore, the position of variable borehole diameter should be located outside the anchorage zone.  
(4) Borehole spacing  
As shown in Figure 10, as the spacing of the variable diameter boreholes increases, the deformation of the roadway surrounding rock decreases, indicating that the damage to the surrounding rock is smaller when the spacing of the boreholes is larger. In the case of spacing of 0.5 m, the increase in the surrounding rock deformation is larger, indicating that  
Figure 8: The curve of roadway surface deformation under different deep borehole diameters: (i-v) horizontal displacement.  
Figure 9: The curve of roadway surface deformation under different variable aperture positions: (i-vi) horizontal displacement.  
in this state, the overall support structure of the roadway surrounding rock is damaged, resulting in a significant increase in deformation.