## 4 Results and Discussion  
### Influence of Different Parameters on Vertical Stress Distribution in the Surrounding Rock  
(1) Shallow borehole diameter  
From Figure 3, it can be seen that when there is no pressure relief borehole in the roadway, the vertical stress peak of the roadway side surrounding rock is 15.3 MPa, which is located on the roadway side at about 6.5 m, and the stress concentration area is larger. With the increase in the diameter of the shallow borehole (80 mm \(\rightarrow\) 300 mm), the peak stress is transferred to the deep part (16.5 m \(\rightarrow\) 16.9 m from the roadway side), the peak vertical stress shows an increasing trend (15.9 MPa \(\rightarrow\) 17.6 MPa), and the vertical stress at the position of the original peak vertical stress shows a decreasing trend (8.6 MPa \(\rightarrow\) 7.6 MPa). The reduction in vertical stress at the original peak location is limited. It shows that the shallow borehole diameter has less influence on the vertical stress of the roadway surrounding rock, mainly because the shallow borehole depth is 4 m, which is in front of the stress peak of the roadway, and has little influence on the stress transfer effect. (2) Deep borehole diameter  
From Figure 4, it can be seen that as the diameter of deep borehole increases (80 mm \(\rightarrow\) 300 mm), the stress peak is transferred to the deeper part (6.6 m \(\rightarrow\) 15.9 m from the roadway side), and the vertical stress peak now shows an increasing trend (14.6 MPa \(\rightarrow\) 16.9 MPa), and the vertical stress at the location of the original vertical stress peak shows a decreasing trend (14.3 MPa \(\rightarrow\) 8.5 MPa). After the diameter of the deep borehole exceeds 250 mm, the reduction in vertical stress at the original vertical stress peak is limited, indicating  
Figure 3: Variation diagram of vertical stress distribution in surrounding rock under different shallow borehole diameters: (**a**) vertical stress, (**b**) stress peak and location, and (**i-vi**) vertical stress simulation cloud diagram. that the pressure relief zones formed by the borehole have penetrated each other, and the stress reduction effect has reached the limit. The main reason why the diameter of the deep borehole has a greater influence on the vertical stress of the surrounding rock is that the location of the variable borehole diameter is at 4 m of the roadway side, and the deep borehole is in the stress concentration area of the roadway surrounding rock. The larger the diameter of the deep borehole, the larger the plastic zone is formed, and the greater the influence on the effect of the stress transfer on the surrounding rock. From Figure 5, with the increase in the distance between the variable aperture position and the roadway side (0 m \(\rightarrow\) 16 m), the position of the stress peak is gradually closer to the roadway side (16.9 m \(\rightarrow\) 6.6 m), and the present peak vertical stress shows a decreasing trend (17.6 MPa \(\rightarrow\) 14.6 MPa), and the vertical stress at the original peak vertical stress position shows an increasing trend (7.6 MPa \(\rightarrow\) 14.3 MPa). When the position of the variable borehole is located in the roadway before the peak vertical stress without pressure relief (\(\leq\)4 m), the original peak vertical stress is reduced to 8.6 MPa, with a reduction of 44.4%. When the variable aperture position is located around the peak vertical stresses in the roadway without pressure relief (6 m), there are two vertical stress concentration zones, and the original peak vertical stress is reduced to 11.9 MPa, with a reduction of 22.2%. When the position of the variable borehole is located after the peak vertical stress position of the roadway (\(\geq\)8 m), the vertical stress at the original peak position is reduced to 13.8 MPa, with a reduction of 9.8%.