## 4 Evolution Law of Front Abutment Pressure and Goaf Stress without Fracturing Conditions  
The corresponding goat pressure and front abutment pressure with the advancing of the No. 8202 working face are extracted, and the vertical stress in the coal seam is selected as the monitoring indicator for the front abutment pressure. In contrast, the collapsed coal gangue in the goaf is updated to the Salamon model, and the vertical stress of the Salamon model is used as the goaf pressure, as shown in Figure 6. When the advancing distance is 50 m, the KS1 is not broken, the goaf stress is basically equal to zero, the stress concentration is formed at the working face, and the open-off cut and the peak value of the front abutment pressure is 22.52 MPa, as shown in Figure 6a. When the advancing distance is 100 m, the KS1 is broken, and KS1 and its controlled strata sink synchronously. At the same time, there is an uncoordinated deformation between KS2 and its underlying rock layer (that is, the strata controlled by KS1), and the separation appears. The width of the stress recovery zone in goaf is 32 m, the peak value of goaf stress is 0.75 MPa, and the peak value of the front abutment pressure is 20.76 MPa, as shown in Figure 6b. When the advancing distance is 150 m, the peak value of the goaf stress increases to 1.43 MPa, the width of the stress recovery zone rises to 81.5 m, and the peak value of front abutment pressure is 21.83 MPa, as shown in Figure 6c. When the advancing distance is 200 m, KS2 is broken, KS2 and its controlled rock layer sink synchronously, the peak value of the goaf stress increases to 2.29 MPa, the width of the stress recovery zone rises to 146 m, and the peak value of the front abutment pressure is 23.23 MPa, as shown in Figure 6d. When the advancing distance is 250 m, the peak value of the goaf stress further increases to 2.61 MPa, the width of the stress recovery zone rises to 198 m, and the peak value of the goaf stress further increases to 198 m, and the peak value of the goaf stress further increases to 24.91 MPa, as shown in Figure 6e. When the advancing distance is 300 m, the peak value of the goaf stress further increases to 2.59 MPa, the width of the stress recovery zone rises to 215 m, and the peak value of the abutment pressure is 25.32 MPa, as shown in Figure 6f.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**No.**} & \multirow{2}{*}{**Name**} & **Elastic** & **Compressive** & **Tensile** & **Poisson’s** & **Cohesion** & **Internal Friction** \\  & & **Modulus** & **Strength** & **Strength** & **Ratio** & **C/MPa** & **Angle** \\  & & **E/GPa** & **\(\alpha_{\text{c}}\)/MPa** & **\(\alpha_{\text{t}}\)/MPa** & **\(\mu\)** & **\(\mu\)** & **\(\mu\)** \\ \hline
1 & Coarse sandstone & 23 & 36.83 & 3.9 & 0.24 & 4.1 & 22 \\
2 & Medium sandstone & 19.5 & 38.6 & 3.7 & 0.25 & 5.1 & 23 \\
3 & Silstone & 18.5 & 23.53 & 2.6 & 0.27 & 4.2 & 22 \\
4 & Fine sandstone & 60 & 90.43 & 12.4 & 0.21 & 8.4 & 25 \\
5 & Silstone & 19.1 & 27.63 & 4.2 & 0.22 & 6.1 & 23 \\
6 & Coal seam & 7.5 & 16.13 & 1.1 & 0.32 & 3.9 & 20 \\
7 & Mudstone & 5.7 & 25.4 & 2.3 & 0.27 & 3.8 & 21 \\
8 & Carbonaceous & 13 & 15.42 & 1.4 & 0.22 & 3.7 & 21 \\
9 & Sandy mudstone & 10.5 & 32.2 & 2.8 & 0.27 & 5.2 & 22 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Numerical simulation of rock formation mechanical parameters.