# Numerical Simulation of Rock Mass Structure Effect on Tunnel Smooth Blasting Quality: A Case Study
## 3 Results and Discussions
### Massive Structure Rock Mass  
Through single factor analysis, the influence curves of various factors in the massive structure rock mass could be obtained, as shown in Figure 12. Among the six numerical test factors, the angle between structural planes had the most significant influence on the overbreak rate of smooth blasting, and the overbreak rate decreased rapidly with the increase in the angle between the structural planes. When the angle between the structural planes increased from 30\({}^{\circ}\) to 90\({}^{\circ}\), the overbreak rate decreased from 6.96% to 3.46%. The slope of the influence curve of the average spacing of structural planes was obviously smaller than that of the angle between structural planes, indicating that the influence of the average spacing of structural planes was second only to the angle between structural planes. For massive structural rock mass, the smaller the angle between structural planes was, the more serious the fragmentation degree of rock mass was. Furthermore, the influence of the angle between structural planes on the fragmentation degree was greater than that of the spacing between structural planes. The influence of peripheral hole spacing was the third, and the smooth blasting overbreak rate decreased slowly with the increase in peripheral hole spacing. The curves of rock density, heading hole spacing, and vertical  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Test No.**} & \multicolumn{6}{c}{**Influence Factor**} & \multicolumn{3}{c}{**Results**} \\ \cline{2-9}  & \(\boldsymbol{\gamma}\) (\({}^{\circ}\)) & \(\boldsymbol{\alpha}\) (\({}^{\circ}\)) & \(\boldsymbol{D}\) (\(\boldsymbol{m}\)) & \(\boldsymbol{P}\) (\(\boldsymbol{cm}\)  
spacing between the peripheral hole and the heading hole were relatively stable on the whole. They exhibited a relatively slight influence on the overbreak rate, hence not the main control factors of overbreak rate, and have relatively slight influence on the overbreak rate, which were not the main control factors of overbreak rate.  
Through the main effect analysis, the maximum membership degree of rock density, the angle between structural planes, the average spacing of structural planes, the peripheral hole spacing, the heading hole spacing, and the vertical spacing between the peripheral hole and the heading hole were obtained, where \(\hat{F}_{\rho}\ =\ 0.208\), \(\hat{F}_{\theta}\ =\ 0.287\), \(\hat{F}_{D}\ =\ 0.246\), \(\hat{F}_{P}\ =\ 0.222\), \(\hat{F}_{H}\ =\ 0.207\), and \(\hat{F}_{S}\ =\ 0.206\), respectively. Considering \(\hat{F}_{\theta}\ >\ \hat{F}_{D}\ >\ \hat{F}_{P}\ >\ \hat{F}_{H}\ >\ \hat{F}_{S}\), the influence weight of these six factors were ordered as the angle between structural planes, average spacing of structural planes, peripheral hole spacing, rock density, heading hole spacing, and vertical spacing between the peripheral hole and the heading hole. The maximum membership degree of the angle between structural planes was 0.287, much higher than the maximum membership degree of other factors, indicating that the angle between structural planes was the biggest influencing factor of the weight. The influence degree of the average spacing of structural planes was the second, and its maximum membership degree was 0.246. Due to the cutting of two groups of structural planes, the smaller the angle between the two groups of structural planes was, the smaller the spacing of structural planes, the more fragmented the rock mass, and the more serious the overbreak was. The peripheral hole spacing with the third largest membership was only 0.222, which was far less than the former two, indicating that the influence of rock mass structure on massive rock mass was far greater than that of blast hole layout.