# 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  
Under the condition of a 95% backfill ratio, a monitoring station is arranged 90 m away from the open-off cut of CT301 panel to observe the distribution of abutment stress in the mining area at working face advance distances of 30, 45, 60, 75, 90, 105, 120, 135, 150, and 165 m, as well as the stress distribution of roadway surrounding rock during the extraction process (Figure 11). In the following description, \"-\" represents that the working face has not yet passed the monitoring station, while \"+\" indicates that the working face has passed the monitoring station. From Figure 11, it can be observed that the abutment stress around the mining area exhibits the same characteristics at different working face advance distances. Both roadways behind the working face and the vicinity of the filling working face are in a state of stress relief. Stress concentration occurs behind the coal wall and on coal rib sides, influenced by the mining-induced stress from the working face and the roof rotation load. High abutment stress increases near both sides of the roadway. From Figure 11a-c, when the advancing distance of the working face is 30 m, 45 m, and 60 m, the abutment stress around the mining area shows an increasing trend. Due to the advancement of the working face, the overlying rock layers of the gob are supported by  
Figure 10: Direct displacement curve of different backfill ratios. the unfrozen, low-strength paste fill. The fill material is compressed, and mining-induced stress becomes evident. The peak abutment stress on the coal rib, the peak advanced abutment stress, and the range of influence of the advanced abutment stress all show an increasing trend. The peak of abutment stresses on the coal rib are 23.08, 25.03, and 26.41 MPa, respectively, and the peak advanced abutment stresses are 21.90, 22.36, and 22.58 MPa. The range of influence of the advanced abutment stress is approximately 8.2, 8.6, and 8.9 m, respectively. From the surrounding rock stress distribution, the distance between the monitoring station and the working face is 60 m to 30 m, where the mining-induced stress is minimal, and the stress is symmetrically distributed on both sides of the reserved roadway. The peak stress is about 17 MPa and occurs approximately 4 m from the roadway. Figure 11: _Cont._  
From Figure 11d,e, when the advancing distance of the working face is 75 m, and 90 m, the analysis of abtment stress around the mining area shows that as the working face advances, the paste fill solidifies and its strength gradually approaches its later strength, enhancing its ability to support the overlying rock layers. The peak abtment stress on the coal rib and the range of influence of the advanced abtment stress show a smaller increase in fluctuation. The peak of abtment stresses on the coal rib are 26.98 MPa and 27.12 MPa, respectively, and the peak advanced abtment stresses are 22.62 MPa and 22.65 MPa. The range of influence of the advanced abtment stress is around 9.0 m. From the surrounding rock stress distribution, the distance between the monitoring station and the working face is 15 m, where the mining-induced stress is significant, and the stress distribution is asymmetric. The stress peak on the working face side is higher than that on the coal rib side. When the monitoring station is 0 m from the working face, the roof above the working face is relieved, and stress concentration increases on the coal rib side. The peak stress is approximately 21 MPa, occurring around 4 m from the roadway.