## 4 Numerical Simulation Analysis of Knife Handle Working Face
### Evolution Rules of Support Pressure of Knife Handle Working Surface  
After the working face is mined, the stress of the coal and rock mass is redistributed; the stress concentration is formed in front and on both sides of the working face. In order to study the advancement distance of the knife handle working face and the evolution trend of the advanced support pressure, the measurement line is arranged at the position of \(x=135\) and \(z=111.5\) in the model. During the process of the working face advancing from 200 m to 400 m, the advanced support pressure was recorded every 20 m, analyzing the distribution characteristics of the leading bearing pressure when the width of the working face changed from 85 m to 137.8 m. It can be seen from Figure 6 that the peak value of the  
Figure 5: Numerical calculation model. advanced support pressure first decreases and then increases. Affected by the gob of the upper layer, the peak value of the advanced support pressure is smaller overall. When the width of the working face is 85 m, as the advancing distance of the working face increases, the peak value of the advanced bearing pressure gradually decreases from 10.75 MPa to 10.31 MPa. The change in advanced support pressure is small, and the influence range of the advanced support pressure is within 57 m in front of the working face; the peak value of the lateral support pressure dropps from 17.43 MPa to 17.23 MPa, and the change in the lateral support pressure is small. When the width of the working face is 137.8 m, the peak value of the advanced support pressure of the working face increases with the increase in the advancing distance of the working face. The peak value of the advanced support pressure increases from 10.31 MPa to 14.62 MPa. The increase in the advanced support pressure is 4.31 MPa. The stress concentration factor increased from 0.88 to 1.25, the peak value of the lateral support pressure along the crossheading on the working surface increased from 17.23 MPa to 24.67 MPa, and the lateral support pressure increased to 7.44 MPa, indicating that when the width of the working surface increases, the overlying rock migration of the roof of the working surface is severe. The vertical stress distribution characteristics when the working face is mined at 200 m are shown in Figure 7. After the coal seam was mined, obvious stress concentration appeared on the headgate and tailgate of the I010206 working face. Affected by the inclination angle of the coal seam, the vertical stress peak value on the headgate was greater than the tailgate. When the width of the working face is 85 m, the peak vertical stress at 10 m of the coal in front of the working face is 16.49 MPa, and the peak vertical stress at 60 m of the coal in front of the working face is 15.72 MPa. The vertical stress decrease is 5.7%. The vertical stress decreases slightly as the distance from the working surface increases. The vertical stress distribution characteristics of the working face when mining at 400 m are shown in Figure 8. As the working face advances, the geometry of the working face roof will affect the stress evolution law of the surrounding rock. When the width of the working face increases from 85 m to 137.8 m, the exposed area of the roof increases and the load transmitted by the overlying rock layer to the surrounding goat also increases, resulting in an increase in the peak vertical stress of the coal mass in front of the working face. The peak vertical stress at 10 m of the coal in front of the working face is 26.56 MPa; the peak vertical stress at 60 m of the coal in front of the working face is 17.87 MPa. The vertical stress decrease is 32.7%. The numerical calculation results show that the extreme value of vertical stress in the large slope is higher when the working face is mined with different widths. When the working face width is 137.8 m, the artificial mining disturbance causes the  
Figure 6: Support pressure distribution characteristics during working face advancement.