## 4 Comparison of the Dynamic Blasting and HPGEM
Shock waves propagate quickly and cause damage to the nearby zone of the explosion, and then decay into stress and seismic waves, while stress waves propagate relatively slowly in the rock mass. The rock mass was moved by the superposition of explosive gases resulting from the shock waves and explosives' explosion, while the disturbance of the rock mass by shock waves precedes the uptake of explosive gases in the rock mass. The vibration generated by the HPGEM is basically from the impact of the high-temperature and high-pressure gas on the expansion of the rock wall, but the impact of the shock wave is relatively weak. As the expansion of the fissures in the rock and the extension of the pressure decrease rapidly, the disturbance of the rock mass will decrease. In general, the further the distance, the faster the disturbance decreases. After understanding the change rule of vibration velocity of the two rock-breaking methods, it is beneficial to compare and analyze the vibration velocities of the two rock-breaking methods when they are employed in difficult engineering sites. Based on the above conclusions and the safety requirements mentioned, the vibration velocities of the HPGEM with the same Q in the limit case were obtained for comparative analysis, as shown in Table 9. Similarly, according to the explosive blasting program in the field, the vibration velocity of the HPGEM with the same Q was also acquired, as displayed in Table 10. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multicolumn{2}{c}{**Location**} & \multicolumn{1}{c}{**Q (kg)**} & \multicolumn{1}{c}{**R (m)**} & \multicolumn{1}{c}{\(PPV_{1}\) (cm/s)} & \multicolumn{1}{c}{\(PPV_{2}\) (cm/s)} & \multicolumn{1}{c}{\(PPV_{2}\)/\(PPV_{1}\)} \\ \hline \multirow{3}{*}{Upper bench} & HR & 6.80 & 13.45 & 6.950 & 1.795 & 0.258 \\  & UP & 6.80 & 14.324.00 & 6.355 & 1.626 & 0.256 \\  & HRL & 6.80 & 56.00 & 0.972 & 0.191 & 0.197 \\ \cline{2-6}  & HR & 4.00 & 12.037.00 & 6.330 & 1.473 & 0.233 \\  & UP & 4.00 & 56.00 & 0.762 & 0.132 & 0.173 \\ \cline{2-6}  & HR & 1.00 & 9.23 & 4.823 & 0.845 & 0.175 \\ \cline{2-6}  & UP & 1.00 & 7.79 & 6.100 & 1.103 & 0.181 \\ \cline{2-6}  & HRL & 1.00 & 50.00 & 0.471 & 0.060 & 0.127 \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Comparison results of \(PPV_{1}\) and \(PPV_{2}\) in the practical case. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Location** & **Q (kg)** & **R (m)** & \(PPV_{1}\) (cm/s) & \(PPV_{2}\) (cm/s) & \(V/V_{1}\) \\ \hline HR & 0.53 & 5.70 & 7 & 1.152 & 0.165 \\ UP & 0.29 & 4.64 & 7 & 1.032 & 0.147 \\ HSRL & 5.15 & 50.00 & 1 & 0.188 & 0.188 \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Comparison of \(PPV_{1}\) and \(PPV_{2}\) in the limit case. As can be seen from Tables 9 and 10, in the case of the same Q of explosives and the gas generating agent explosion, the vibration velocity of the HPGEM with various engineering difficulties is much lower than that of the explosives' blasting method. Moreover, it can be seen from the ratio of vibration velocity that the vibration velocity control efficiency of the HPGEM in the actual operable procedure is basically lower than in the limit case. This is due to the different locations of the three major engineering difficulties. Considering that the excavation design program must be practical to operate, the Q and the R will be adjusted accordingly. However, the smaller vibrations produced by the HPGEM demonstrated its advantage in controlling vibration hazards. According to the maximum allowable vibration velocity set at each engineering difficulty in the limit case, the maximum section charges of the two rock-breaking methods at each engineering difficulty were back-calculated using the fitting formula obtained from dynamic blasting and HPGEM in the test tunnel (for the HPGEM, it is the quality of single consumption).