## 4 Industrial Experiment
### The Control Effect of the Surrounding Rock in the Gob-Side Entry  
Five surface displacement monitoring stations are arranged along the gob-side entry section of the 15,150 working face (already left). A new station is installed every 40 m as the entry advances. The overall layout of the stations is shown in Figure 28.  
(1) Roadway surrounding rock displacement observation. Displacement monitoring of the gob-side entry surrounding rock was carried out at monitoring stations NO.1, NO.2, NO.3, and NO.4, as shown in Figure 29. The surrounding  
Figure 28: Layout diagram of comprehensive station. Figure 27: Schematic diagram of strengthening support of roadway-side support: (**a**) vertical to the direction of gob-side entry retaining; (**b**) parallel to the direction of gob-side entry retaining. Figure 26: On-site construction drawings. rock of the 15,150 working face gob-side entry deforms to a certain extent due to mining disturbance, but compared to the large cross-sectional roadway, the deformation is relatively small, and the stability of the roadway-side support is high. During the advancement of the working face, the changes in the horizontal displacement of the roadway roof and the gob-side support body are basically consistent. Displacement increases began to appear in the surrounding rock when the working face was 80-90 m ahead. The maximum displacement of the roof at the NO.1 station was 27 mm, and at the NO.2 station, it was 26.3 mm. The maximum displacement of the side of the roadway-side support at the NO.1 station was 32.44 mm, and at the NO.4 station, it was 31.29 mm. When the distance to the working face reached 150 m, the surrounding rock deformation gradually stabilized. (2) Anchor bolt and anchor cable load observation. The force monitoring results of the pull-back anchor bolts for the gob-side support at station NO.5 are shown in Figure 30. The measuring tool chosen is the bolt stress meter. When stress changes occur within the measured structure, the bolt stress meter is subjected to tension or compression. By reading the data from the dial, the force acting on the bolt at that moment can be determined. The force on the pull-back anchor bolts in the gob-side entry of the 15,150 working face gradually stabilized around the 13 th day. The anchor bolt force initially decreased and then gradually increased, eventually maintaining around 115 kN. The maximum yield strength of the same model threaded steel pull bolts is 60.5% of the maximum yield load, which is 189.97 kN. During the axial force observation period, there were no instances of anchor bolt breakage or failure, indicating that the support design meets safety requirements and ensures the production safety of the working face. Figure 30: The observation results of the force of the tension bolt of the roadside support body of the NO.5 station. Figure 29: Observation of displacement of surrounding rock in roadway under 15,150 working face: (a) roof subsidence; (b) horizontal displacement. No bolt breakage or failure occurred during the axial force observation period, indicating that the support design meets the safety design requirements and ensures the production safety of the working face. (3) Deep roof surrounding rock displacement monitoring. The displacement of the deep roof surrounding rock at stations NO.1 and NO.3 was monitored, and the results are shown in Figure 31.  
As the working face advanced, the deformation of the tunnel roof surrounding rock gradually increased. When the monitoring station was located 100 m away, the deep surrounding rock displacement remained consistent. At 80 m from the measurement station, the deformation rate began to slowly increase. After the working face advanced to 40 m from the measurement station, the deformation rate of the transport tunnel slowed down. The displacement of the 4 m baseline point at station No.1 increased from 0.001 mm to 16.2 mm, and the 10 m deep baseline displacement was 12.6 mm.