## 5 Working Face Abandoned Roadway Filling Technology Process
### Observation of Mine Pressure  
Mine pressure observation was carried out in the process of mining the back of the 3122 comprehensive faces, to analyze the mine pressure manifestation law of the 3122 comprehensive faces after filling the abandoned roadway and the peripheral rock deformation of the transport roadway. Two end hydraulic supports were selected in the part of the working face close to the end of the transport roadway to carry out the observation of the support resistance, record the change rule of the hydraulic support resistance with the advancing distance of the working face, and set the displacement measurement station in the transport roadway at a distance of 30 m from the cutting-off. At the same time, a displacement station was set 30 m from the cutting-off in the transport roadway to observe the roof subsidence and the displacement of the roadway gang in the transport roadway, as shown in Figure 17.  
The Jingxin Coal Industry 3122 comprehensive face end hydraulic support model ZT11600/18/26 pump station has a working pressure of 31.5 MPa and an initial support force of up to 8728 KN. As shown in Figure 18, the working face hydraulic support resistance distribution curve can be seen, and the 3122 comprehensive face in the process of mining has not been found in the mining anomalies. The 2# hydraulic support working resistance is slightly greater than the 1# hydraulic support resistance, presumably due to the 2# hydraulic support being closer to the transport roadway in the part of the vertical contact between the abandoned roadway and the working face. Table 4 is based on the hydraulic support resistance distribution curve statistics of the pressure step distance. The mine pressure is not obvious during the mining. From the 1# hydraulic support, the cycle pressure step of the 3122 working face is 10 m, and the initial pressure step is 18 m. From the 2# hydraulic support, the cycle pressure step of the 3122 working face is 11 m, and the initial pressure step is 12 m.  
Figure 16: Abandoned roadway filling effect. To monitor peripheral rock deformation in the transport roadway, displacement monitoring points are strategically placed to track top and bottom plate sinking and peripheral rock movement towards the two gangs. Figure 19 illustrates the arrangement of these monitoring points. Displacement observation on the roadway surface follows a 'cross' distribution method. At the 3122 transport roadway measuring station, four measuring base points--W, S, G, and H--are selected. Holes are drilled, and pins are installed at these points to record top and bottom slab deformation as well as gang movement. Base \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Hydraulic Support Number**} & \multirow{2}{*}{**Initial Pressure Appearance Distance/m**} & \multicolumn{3}{c}{**Cycle to Pressure Distance/m**} & \multicolumn{2}{c}{**Average Cycle to Pressure Distance/m**} \\ \cline{3-6}  & & **1** & **2** & **3** & **4** & **Pressure Distance/m** \\ \hline
1\# & 18 & 10 & 8 & 10 & 12 & 10 \\
2\# & 16 & 8 & 12 & 12 & 12 & 11 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Working face pressure step distance. Figure 17: Survey station layout schematic. Figure 18: The distribution diagram of the working resistance. points W and S align with the centerline of the roadway, while G and H are positioned at the waistline. The observation results of surface displacement of the 3122 transport roadways are shown in Figure 20. From the figure, it can be seen that, during the mining process of the 3122 working face, the maximum relative displacement of the top and bottom plates of the transport roadway is 142 mm, and the maximum relative displacement of the two gangs is 95 mm. When the working face advances to 30-40 m, nearing the displacement station, the deformation rate of the top and bottom plates of the transport roadway and the two gangs peaks.