## 4 Study on Mining Layout Pattern Based on Numerical Simulation
### Influence of Panel Mining Scale on the Stability of Panel-Isolated Coal Pillar  
When the width of the panel-isolated coal pillar is 200 m and 250 m, the vertical stress tendency slice contour and elastic strain energy plane distribution contour of the panel-isolated coal pillar area after excavation in the second and third panels under different panel mining scales are shown in Figures 12 and 13. With the increase in the mining scale in the third panel, the degree of stress concentration and energy accumulation in the panel-isolated coal pillar area intensifies. Under the condition of a 200 m-wide panel-isolated coal pillar, when the mining scale in the third panel is less than 400 m, the degree of stress concentration and elastic strain energy accumulation in the panel-isolated coal pillar area is relatively low. There is only a stress concentration area near the goat on both sides. When the mining scale in the third panel exceeds 520 m, the degree of stress concentration and elastic strain energy accumulation in the elastic core area in the middle of the isolated coal pillar area becomes higher, and the stress concentration area gradually develops to the top of the coal seam. Under the condition of a 250 m-wide panel-isolated coal pillar, when the mining scale in the third panel reaches 700 m and 730 m, the stress and energy accumulation area gradually evolve towards the elastic core area in the middle of the coal pillar. When the mining scale in the third panel reaches 760 m, the degree of stress concentration and elastic strain energy accumulation in the elastic core area in the middle of the panel-isolated coal pillar area becomes higher, and a stress concentration area appears in the roof rock layer. Draw the stress variation curve along the inclination of the isolated coal pillar area under different panel mining scale, as shown in Figure 14. With the increase in the panel mining scale, the degree of stress concentration in the panel-isolated coal pillar area increases. Under the condition of a 200 m-wide panel-isolated coal pillar, the stress peak increases from 51.55 MPa to 54.98 MPa, and the stress concentration factor increases from 2.17 to 2.31. When the width of the mining scale of the panel is 550 m, the vertical stress peak in the panel-isolated coal pillar area is 54.08 MPa, exceeding the uniaxial compressive strength of three times the coal, which is 54 MPa. At this point, the isolated coal pillar in the panel area was in a critical and unstable state. Under the condition of a 250 m-wide  
Figure 12: Slice contour of vertical stress tendency in the panel-isolated coal pillar area under different mining scales of panel. (**a**) 200 m-wide panel-isolated coal pillar. (**b**) 250 m-wide panel-isolated coal pillar. isolated coal pillar, the stress peak increases from 49.78 MPa to 55.83 MPa, and the stress concentration factor increases from 2.10 to 2.35. When the width of the mining scale of the panel is 700 m, the vertical stress peak in the panel-isolated coal pillar area is 54.75 MPa, exceeding the uniaxial compressive strength of three times the coal, which is 54 MPa. At this point, the panel-isolated coal pillar was in a critical and unstable state. Analyzing the above simulation results reveals that with the increase in the mining scale of the small panel, the transferred stress from the goat on both sides of the panel-isolated coal pillar increases. However, with the width of the panel-isolated coal pillar remaining unchanged, the average bearing stress of the coal pillar increases, leading to the panel-isolated coal pillar approaching a critical state of instability. Considering the stability of the panel-isolated coal pillar and the resource recovery rate, combined with the simulation results mentioned above, under the condition of a 200 m-wide panel-isolated coal pillar, the reasonable mining scale for the small panel is between 490 m and 550 m, and the mining district recovery ratio is between 75% and 78%.