# Risk Assessment of Compound Dynamic Disaster Based on AHP-EWM
## 5 Risk Evaluation of Compound Dynamic Disaster
### Field Application of Evaluation Methods  
The assessment object is the second mining area of mine B in the Pingdingshan mining area, where the minimum mining depth exceeds 800 m, with an average of 910 m. The thickness of the coal seam is 0.35-4.46 m, with an average of 1.47 m. There is one layer of dirt band with a thickness of 0.18-0.70 m. The dip angle of the coal seam is 9-11\({}^{\circ}\). The roof is sandstone, and the bottom is argillaceous sandstone. The maximum gas pressure of the coal seam is 1.2 MPa and the maximum gas content is 8.18 m\({}^{3}\)/t measured at the 800 m level. See Table 5 for specific data. Since 2000, there were a total of eight compound dynamic disasters in the coal seam where the mining area was located with adjacent coal seams. Geological information of the second mining area is shown in Figure 4. \begin{table}
\begin{tabular}{c c c c c c c} \hline
**Target Layer** & **Primary Index** & **Secondary Index** & **Unit** & **Working Face 1** & **Working Face 2** & **Working Face 3** \\ \hline \multirow{6}{*}{Risk degree of compound dynamic disaster U} & \multirow{3}{*}{Geological Factors U\({}_{1}\)} & Mining depth U\({}_{1}\) & m & 1039 & 880 & 960 \\  & & Fault scale index U\({}_{12}\) & - & 0.05 & 0.05 & 0.05 \\  & & Characteristic parameter of roof rock & - & 44.2 & 50.3 & 41 \\  & & \multicolumn{2}{c}{Change of coal scan thickness U\({}_{14}\)} & - & 3 & 1 & 3 \\  & & Plane deformation coefficient U\({}_{5}\) & - & 3.28 \(\times\) 10\({}^{-5}\) & \(6.54\times 10^{-6}\) & \(1.50\times 10^{-6}\) \\ \cline{2-6}  & & Impact energy index U\({}_{21}\) & - & 1.68 & 2.28 & 3.57 \\  & & Elastic energy index U\({}_{22}\) & - & 3.87 & 2.97 & 3.02 \\  & & Dynamic failure time U\({}_{23}\) & ms & 346 & 4.84 & 542 \\  & & Residual gas content U\({}_{34}\) & m\({}^{3}\)/t & 16.2 & 10.2 & 13.62 \\  & & Residual gas pressure U\({}_{53}\) & MPa & 1.5 & 0.6 & 0.72 \\  & & Firmness coefficient U\({}_{22}\) & - & 0.29 & 0.4 & 0.3 \\  & & Initial speed of gas release U\({}_{27}\) & mL/s & 13.22 & 12.3 & 13.1 \\ \cline{2-6}  & & Coefficient of the protective layer U\({}_{31}\) & - & 3 & 2 & 3 \\  & & Influence of goal U\({}_{22}\) & - & 1 & 1 & 1 \\  & & Mining speed U\({}_{33}\) & m/d & 4 & 3.5 & 42 \\  & & Working face length U\({}_{34}\) & m & 265 & 248 & 256 \\ \hline \end{tabular}
\end{table} 
Table 4: Basic data of each working face in the fourth mining area of mine A in the Pingdingshan mining area. \begin{table}
\begin{tabular}{c c c c c c} \hline
**Target Layer** & **Primary Index** & **Secondary Index** & **Unit** & **32,020 Working** & **32,040 Working** & **32,010 Working** \\  & & Mining depth U\({}_{1}\) & & **Face** & **Face** & **Face** \\ \hline \multirow{6}{*}{Risk degree of compound dynamic disaster U} & \multirow{3}{*}{Geological factors U\({}_{1}\)} & Mining depth U\({}_{1}\) & m & 937 & 968 & 944 \\  & & Fault scale index U\({}_{12}\) & - & 0.02 & 0.01 & 0.01 \\  & & Characteristic parameter of roof rock & - & 53.2 & 51.9 & 37.1 \\  & & stratum thickness U\({}_{14}\) & - & 1 & 1 & 1 \\  & & Change of coal seam thickness U\({}_{14}\) & - & 1 & 1 & 1 \\  & & Plane deformation coefficient U\({}_{53}\) & - & \(4.78\times 10^{-6}\) & \(5.60\times 10^{-6}\) & \(6.40\times 10^{-6}\) \\ \hline \end{tabular}
\end{table} 
Table 5: Basic data of each working face in the second mining area of mine B in the Pingdingshan mining area.