# Study on the Stability and Control of Gob-Side Entry Retaining in Paste Backfill Working Face
## 5 Results of Numerical Simulation
### Evolution Law of Abutment Stress in the Process of Advancing Working Face
Figure 11: Evolution law of abtment stress in different advancing distances of the mining site: (**a**) advance 30 m; (**b**) advance 45 m; (**c**) advance 60 m; (**d**) advance 75 m; (**e**) advance 90 m; (**f**) advance 105 m; (**g**) advance 120 m; (**h**) advance 135 m; (**i**) advance 150 m; (**j**) advance 165 m.  
From Figure 11f,g, when the advancing distance of the working face is 105 m and 120 m, the abutment stress around the mining area shows that the peak abutment stresses on coal rib are 27.12 MPa and 27.11 MPa, respectively, and the peak advanced abutment stresses are 22.54 MPa and 22.56 MPa. The range of influence of the advanced abutment stress is approximately 9.0 m. At this point, the paste fill has completely solidified and reached its designed compressive strength, significantly enhancing its ability to support the overlying rock layers. The range has exceeded 135 m from the open-off cut, marking the end of the periodic pressure buildup. The overlying rock layer no longer experiences significant movement, and the rock layer activity stabilizes, with the fill material and the overlying rock forming a stable system. From the surrounding rock stress distribution, the distance between the monitoring station and the working face is between \(-\)15 and \(-\)30 m, where the stress distribution on both sides of the reserved roadway is asymmetric due to mining-induced stress. The stress concentration on the coal rib side continues to increase, with the peak stress around 25 MPa. Meanwhile, the fill material gradually exerts its bearing capacity, and the roof above the working face progressively recovers to the original rock stress level. From Figure 11h-j, when the advancing distance of the working face is 135 m, 150 m, and 165 m, the analysis of abutment stress around the mining area shows that the peak abutment stresses on the coal rib are 27.09, 27.08, and 27.07 MPa, respectively, and the peak abutment stresses are 22.56, 22.50, and 22.49 MPa. The range of influence of the advanced abutment stress is approximately 9.0 m. Due to the support action of the fill material, as the working face advances, the gob is filled more completely, and the activity of the overlying rock layer becomes increasingly stable. The range of influence of the advanced abutment stress becomes more stable. From the surrounding rock stress distribution, the distance between the monitoring station and the working face is between \(-\)30 m and \(-\)75 m, at which point the fill material is gradually exerting its maximum bearing capacity. The concentration of the abutment stress on the coal rib fluctuates within a smaller range, with peak stress values of around 26.25, 26.79, and 27.03 MPa, respectively. The activity of the overlying rock is not intense, and the stress level of the roof above the working face gradually recovers to the original rock stress. In the filling area, a measurement line was arranged along the working face direction to extract the vertical stress at different advance distances. The distribution of vertical stress in the fill area at various advance distances is shown in Figure 12.  
From Figure 12, it can be observed that at different advancement distances, under the influence of mining-induced stress and the support effect of the fill material, the vertical stress in the fill area behind the working face follows a pattern of rapid growth until it stabilizes. The vertical stress in front of the working face shows a pattern of initially increasing to a peak stress value before stabilizing. When the working face advances from 30 m to 90 m, the vertical stress in the fill area increases as the advancement distance grows, with the stable stress rising from 6.57 MPa to 9.18 MPa. From 90 m to 165 m, as the paste strength reaches its later stage and the compacted fill length behind the working face increases, the load-bearing capacity stabilizes. The vertical stress in the fill area becomes more stable, with the stable stress consistently at 9.18 MPa.