## 3 Field Test
### Analysis of the Results  
The fracturing status of the drilling holes in the return roadway of the I030902 working face and the layout of measurement points are shown in Figure 13b. The length of the fracturing section is 100 m, and the length of the non-fracturing section is 100 m. A total of 20 measurement points are set: 1\(\mu\), 2\(\mu\), 3\(\mu\), 4\(\mu\), 5\(\mu\), 6\(\mu\), 7\(\mu\), 8\(\mu\), 9\(\mu\), 10\(\mu\), 11\(\mu\), 12\(\mu\), 13\(\mu\), 14\(\mu\), 15\(\mu\), 16\(\mu\), 17\(\mu\), 18\(\mu\), 19\(\mu\), and 20\(\mu\). The distance between each point is 10 m. Each measurement point includes equipment for monitoring roof and floor convergence, the two sidewall convergences, and the anchor bolt strain gauge. A cross-point layout method is used to monitor the convergence of the roof and floor, and the sidewall convergence of the tunnel, while the anchor bolt strain gauge is used to monitor side stress changes in the coal pillar. Monitoring data are collected from each measurement point every 10 m of tunnel excavation. The following conclusions can be drawn from the analysis of the average resistance of the supports in the working face (Figure 14):  
1. Cutting the roof to relieve pressure artificially disrupts the roof rock strata, causing changes in its structure. After roof cutting, the continuity of the roof rock strata, which are originally intact and under high stress, breaks, and its hanging roof effect is weakened. The average resistance of the supports in the fracturing area is significantly lower than that in the middle and upper sections of the working face, with a particularly noticeable decrease when compared to the middle section excavation direction. Figure 13: Station arrangement: (**a**) working face hydraulic support distribution diagram; (**b**) layout of measuring station in air return roadway. 2. The average resistance of the supports in the working face begins to decrease before the fracturing zone fracture, indicating that the influence area of fracturing extends more than 34 m along the inclination projection direction of the fracturing drilling hole in the working face. 3. Based on four sets of recorded data, when the working face excavated 100 m, the average resistance of the supporting structure in the upper part of the working face is 7253.1 kN, in the middle part it is 8690.2 kN, and in the fractured area it is 5486.0 kN. The support resistance in the pressure relief area is reduced by 24.3% and 36.8% compared to the upper and middle sections of the working face, which indicates a good pressure relief effect. The monitoring and analysis of the resistance of the supporting structure after each excavation cycles in the 100-200 m section of the working face show that the periodic step distance of the pressure at the working face is 20 m. Figure 15 shows the mining pressure curve based on the resistance of the supporting structure after each of the excavation cycles at hydraulic supports 33# in the upper part of the working face, 110# in the middle part, and 154# in the fractured impact area during the 200-300 m excavation (fracturing test section). The periodic pressure increase is judged by data points greater than the sum of the average support cycle end resistance (\(P\)) and its standard deviation (\(\sigma\)). From the figure, it can be observed that the maximum pressure for support 33# is 12,355.66 kN, with an average pressure of 7724.6 kN. The periodic pressure step distance ranges from 11 to  
Figure 14: The average resistance of the supporting structure at the working face: (**a**) the working face excavated 25 m; (**b**) the working face excavated 50 m; (**c**) the working face excavated 75 m; (**d**) the working face excavated 100 m.  
19 m, and the average step distance is 17 m. The maximum pressure for support 110# is 12,153.69 kN, with an average pressure of 8064.0 kN. The periodic pressure step distance ranges from 14 to 20 m, and the average step distance is 15.4 m. The maximum pressure for support 154# is 12,040.18 kN, with an average pressure of 8198.3 kN.