## 4 Comparison of the Dynamic Blasting and HPGEM
The results of the comparative analysis are shown in Table 11. The minimum value of 0.6 kg/m\({}^{3}\) is taken for the single consumption of dynamic blasting for rocks with hardness coefficients f = 9-15, which is less than the actual single consumption of dynamite blasting. In this case, the maximum segmented Q can produce the maximum amount of rock breakage. Comparison is made with the calculation results of the HPGEM tests to demonstrate the advantages of the HPGEM in terms of the amount of rock breaking and the control of vibration hazards. As can be seen from Table 11, at the maximum vibration velocity in the limit case, to protect the highway roadbed, underground pipelines and high-speed rail line, the maximum masses of gas agent required for a single initiation of blasting in the high-pressure gas expansion method are 13.103, 15.327 and 10.839 times the maximum sectional charge in dynamite blasting, respectively; while the volumes of the rock breakage in the high-pressure gas expansion method are 9.037, 10.570 and 7.475 times those in dynamite blasting, respectively. In other words, the high-pressure gas expansion method can use more mass of agent than dynamite blasting at one time, without having to be overly limited to segmentation, and can obtain far greater volumes of the rock breakage than dynamite blasting. At the same vibration rate, high pressure gas expansion is also more conducive to increasing the volume of rock breakage. Considering the feasibility of the actual tunnel excavation program, comparisons of the maximum vibration velocity and the amount of rock breakage under the single maximum charge quantity in the limit case are shown in Table 12, where the unit explosive is the corresponding to actual unit consumption. To protect the highway roadbed, underground pipelines and high-speed rail line, the upper bench, the lower bench, and guide blasting are used for three detonations. In the upper-bench rock breaking, the maximum mass of gas generating agent used in the high-pressure gas expansion method is 6.89, 6.98 and 10.15 times the maximum charge in the dynamite blasting, while the rock-breaking volume is 7.23, 7.33 and 10.65 times, respectively. In the lower-bench rock breaking, the maximum mass of gas generating agent used in the high-pressure gas expansion method is 8.0 and 12.2 times of the maximum charge in the dynamite blasting, while the rock-breaking volume is 6.67 and 10.16 times, respectively. In the guide blasting rock breaking, the maximum mass of gas generating agent used in the high-pressure gas expansion method is 11.99, 11.46, and 19.06 times the maximum charge in the dynamite blasting, while the \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Location**} & \multirow{2}{*}{\begin{tabular}{c} _PPV\({}_{i}\)_ \\ **(cm/s)** \\ \end{tabular} } & \multirow{2}{*}{**R (m)**} & \multicolumn{4}{c}{**Dynamic blasting**} & \multicolumn{4}{c}{**HPGEM**} & \multirow{2}{*}{\
\begin{tabular}{c} **m\({}_{\text{J}}\)/m\({}_{\text{A}}\)** \\ **(kg/m\({}^{3}\))** \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} **A\({}_{\text{J}}\)/A\({}_{\text{J}}\)** \\ **(kg/m\({}^{3}\))** \\ \end{tabular} } \\ \cline{5-10}  & & & & & & & & & & \\ \hline HR & 7 & 5.7 & 0.53 & & 0.881 & 6.930 & & 7.965 & 13.10 & 9.04 \\ UP & 7 & 4.64 & 0.29 & 0.6 & 0.475 & 4.372 & 0.87 & 5.026 & 15.33 & 10.57 \\ HSRL & 1 & 50 & 5.15 & & 8.576 & 55.776 & & 64.110 & 10.85 & 7.48 \\ \hline \hline \end{tabular}
\end{table} 
Table 11: Comparison of maximum Q at one time and rock-breaking volume at the PPV in the limit case. rock-breaking volume is 12.34, 11.80, and 19.63 times, respectively. In the limit case, the high-pressure gas expansion method can break rock in a single blasting using a much larger charge than dynamite blasting, and can obtain a much larger rock-breakage volume than dynamite blasting.