## 5 Results and Discussion
### Characteristics of Deviatoric Stress Distribution  
Figure 13 illustrates the distribution of deviatoric stress. From the graph, it can be observed that, for the 4203 panel adjacent to the goat, with varying coal pillar widths, the distribution of deviatoric stress in the surrounding rocks along the 4203 tailgate after excavation in the goat area exhibits different patterns. Under different coal pillar widths, a low deviatoric stress zone (less than 10 MPa) is formed in the shallow surrounding rocks. The deviatoric stress values at the bottom are significantly lower than those at the two sides and the roof, indicating that under these geological conditions, the roof and the two sides are more susceptible to deviatoric stress and exhibit greater deformation compared to the bottom. Figure 12: Vertical stress distribution in 4201 goat. Figure 13: Distribution of deviatoric stress. After the formation of the goat-side roadway, when the coal pillar width is 6 m, high deviatoric stress zones are generated at a depth of 3 m on the coal pillar side and at a depth of 1 m at the roof and bottom corners on the mining side, with peak values of 16.4 MPa and 19 MPa, respectively. At this point, the deformation of the 4301 tailgate mainly concentrates at the roof and bottom corners on the coal pillar side. When the coal pillar width is 9 m, the peak deviatoric stress zone on the coal pillar side is located at a depth of 4 m, and the width of the core area expands from the original 1 m to 2.5 m, with a peak value of 19 MPa. The concentration zones at the roof and bottom corners on the mining side shift towards the interior of the coal body, with the depth increasing from 1 m to 1.5 m at the roof corner and the peak value reaching 17.5 MPa, and from 1 m to 2 m at the bottom corner with the peak value reaching 17 MPa. When the coal pillar width is 12 m, the core area of deviatoric stress concentration on the coal pillar side tends to stabilize and no longer expands. A deviatoric stress reduction zone with a peak value of 10 MPa is generated at a depth of 5.5 m, dividing the deviatoric stress concentration zone of the coal pillar into two parts, with peak values of 16 MPa and 17 MPa, respectively, while on the mining side, the deviatoric stress concentration zone originally shifted from the roof and bottom corners to the roof corner, with the depth increasing from 1.5 m to 2 m and the peak value reaching 17 MPa. When the coal pillar width is 15 m, the deviatoric stress reduction zone on the coal pillar side has a peak value of 8.6 MPa, with a core area width of 7 m, and the peak values of the two parts on the coal pillar are still 16 MPa and 17 MPa, respectively. When the coal pillar width increases to 18 m, the right part of the deviatoric stress concentration zone starts to shift from the middle to the lower part, with a depth of 1 m from the bottom corner and a peak value of 18 MPa. The right part of the concentration zone on the mining side also starts to shift from the middle to the lower part, with a depth of 1 m from the bottom corner and a peak value of 18 MPa. When the coal pillar width increases to 21 m, the core area of deviatoric stress concentration inside the coal pillar exhibits a clear separation feature, forming two independent parts. The right part continues to shift to the lower part, with a depth of 1 m from the bottom corner of the roadway and a peak value of 16 MPa, while at this time, the high deviatoric stress zone on the mining side is located at a depth of 2 m from the roof corner, with a peak value of 14 MPa. The deformation of the roadway mainly occurs at the left bottom corner and the right roof corner. In summary, with the increase of the coal pillar width, the high deviatoric stress concentration zone shifts from the mining side to the coal pillar side. At the same time, a deviatoric stress reduction zone gradually forms on the coal pillar side, dividing the deviatoric stress concentration zone into two parts.