# Factors Influencing the Stability of a Slope Containing a Coal Seam in a Goal
## 4 Analysis of the Influencing Factors  
### Single-Factor Simulation  
By consulting the data and referring to our engineering experience, we designed a single-factor simulation analysis. Table 8 shows the values of the coal seam position H, the roadway width W, the slope gradient i, the coal seam thickness T, the roadway position S, the mining depth and mining thickness ratio R, the coal seam cohesion c, the coal seam internal friction angle \(\varphi\), and the coal seam inclination angle \(\alpha\). Taking the slope calculation model in Section 3.1 as the basic model, we analyzed the influence of the above single factors on the stability of the slope containing a coal seam in a goal by changing the parameter, while the other factors remained unchanged. The analysis and calculation results are shown in Figure 8.  
When other factors were kept the same, as in the basic model in Section 3.1, we found, as shown in Figure 9a, that when the coal seam position was changed, with the decrease in the coal seam position, the slope stability coefficient remained unchanged at first (2.5 \(<\) H \(<\) 5.5) and then sharply dropped (5.5 \(<\) H \(<\) 11.5). We found that with increasing roadway width, the slope stability coefficient gradually decreased. Changing the slope gradient, with the increase in the slope gradient, the slope stability coefficient gradually decreased. With the increase in the coal seam thickness, the slope stability coefficient gradually decreased. When changing the roadway position, with the horizontal distance from the slope foot changing from \(-\)15 to 15 m, the slope stability coefficient first decreased (\(-\)15 \(<\) S \(<\) 0) and then increased (0 \(<\) S \(<\) 15), which was almost symmetrical, but the change range was small, at less than 0.05. Figure 9b shows that with the increases in the mining depth and the mining thickness ratio, the slope stability coefficient first increased (5 \(<\) R \(<\) 15) and then remained unchanged (15 \(<\) R \(<\) 35); changing the cohesion of the coal seam, with the \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Simulation**} & \multicolumn{3}{c}{**Actual Working Conditions**} \\ \hline Slope stability & post-rainfall instability and collapse & post-rainfall instability and collapse & post-rainfall instability and collapse & collapse \\ Sliding surface & coal seam & coal seam & coal seam & coal seam \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Comparison between the MIDAS GTS simulation and the actual working conditions. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Factor** & **1** & **2** & **3** & **4** & **5** & **6** & **7** \\ \hline \(H\) (m) & 2.5 & 4 & 5.5 & 7 & 8.5 & 10 & 11.5 \\ \(W\) (m) & 2.0 & 3.5 & 5.0 & 6.5 & 8.0 & 9.5 & 11.0 \\ \(i\) (\({}^{\circ}\)) & 30 & 35 & 40 & 45 & 50 & 55 & 60 \\ \(T\) (m) & 0.5 & 1.0 & 1.5 & 2 & 2.5 & 3 & 3.5 \\ \(S\) (m) & \(-\)15 & \(-\)10 & \(-\)5 & 0 & 5 & 10 & 15 \\ \(R\) & 5 & 10 & 15 & 20 & 25 & 30 & 35 \\ \(C\) (kPa) & 7 & 9 & 11 & 13 & 15 & 17 & 19 \\ \(\varphi\) (\({}^{\circ}\)) & 14 & 16 & 18 & 20 & 22 & 24 & 26 \\ \(\alpha\)/(\({}^{\circ}\)) & \(-\)15 & \(-\)12.5 & \(-\)10.0 & \(-\)7.5 & \(-\)5.0 & \(-\)2.5 & 0.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Single-factor value ranges. increase in the coal seam cohesion, the slope stability coefficient gradually increased. With the increase in the internal friction angle of the coal seam, the slope stability coefficient gradually increased. When the coal seam dip angle changed from \(-15^{\circ}\)to \(0^{\circ}\), the slope stability coefficient gradually increased. Figure 9: Stability coefficient of a slope containing a coal seam in a goaf under different influencing factors. (**a**) influencing factors: the coal seam position, the roadway width, the slope gradient, the coal seam thickness and the roadway position; (**b**) influencing factors: the mining depth and mining thickness ratio, the coal seam cohesion, the coal seam internal friction angle and the coal seam dip angle.