## 4 Field Tests and Analyses
### Field Tests
#### 4.2.2 Full-Section Blasting Test  
In order to facilitate a comparative and analytical assessment of the blasting effects associated with the combined long and short hole cutting method in the context of full-section blasting, data pertaining to blasting operations were collated five times each for oblique cutting test 1, oblique cutting test 2, the and combined long and short hole cutting method conducted under identical conditions. Among them, the blast hole layouts of oblique cutting test 1 and oblique cutting test 2 are similar, with slight differences in the number and vertical spacing of cutting holes, as well as the single-hole charge of various blast holes. The detonation times of the electronic detonators for the two types of oblique cutting methods were 0 ms, 100 ms, 200 ms, 400 ms, and 600 ms. The detonation time of the combination of long and short holes was divided into seven segments, with a total explosion time extension of 400 ms. The depth of the cutting holes was 2.8 m, with the total numbers of blast holes being 49, 43, and 49, respectively, and the total charge amounts being 60.9 kg, 62.1 kg, and 63 kg, respectively. The range of data from a total of 15 blasting tests is as follows: the tunnel blasting excavation cross-sectional area ranged from 11.7 m\({}^{2}\) to 12.58 m\({}^{2}\), the cycle footage ranged between 1.6 m and 2.5 m, the blasted rock volume ranged from 21.22 m\({}^{3}\) to 26.69 m\({}^{3}\), the explosive consumption per unit volume of rock mass ranged from 2.29 kg/m\({}^{3}\) to 2.75 kg/m\({}^{3}\), the over-excavation depth ranged from 5 cm to 30 cm, and the under-excavation length ranged from 0 to 10 cm. The full section blasting effect of the combined long and short holes is shown in Figure 9. The outcomes of all blasting trials are presented in Table 8. It can be observed that  
Figure 8: The formation of the groove cavity after cut blasting: (**a**) drilling of cutting holes; (**b**) effect of cutting. the blasting footage for the oblique cutting scheme is typically not greater than 2 m, while when using the combined long and short hole cutting method, the blasting footage values are all above 2 m, with a maximum of 2.5 m. The unit consumption of explosives is also relatively low, which can meet the requirements of engineering for efficient tunnelling with reduced consumption. In terms of over-excavation control, the main considerations are the form of the cutting and the impact of the position of the surrounding holes. With the spacing and angle of the surrounding holes remaining unchanged, the surrounding holes of test sites 1 to 5 were moved inward from the outer contour line of the tunnel by 0 cm, 3 cm, 5 cm, 8 cm, and 10 cm in sequence. As can be seen from the data in Table 8, there is no obvious pattern in the amount of under-excavation, but the amount of over-excavation shows a significant downward trend. When the inward movement exceeds 5 cm, the reduction in the amount of over-excavation can reach 10 to 20 cm; after moving inward by 10 cm, the average \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Field Test**} & \multirow{2}{*}{**Test Site**} & \multicolumn{2}{c}{**Explosive Unit**} & \multirow{2}{*}{**Footage/m**} & \multicolumn{2}{c}{**Over-**} & \multicolumn{1}{c}{**Under-**} \\  & & **Consumption/kg/m\({}^{3}\)** & & & **Excavation/cm** & **Excavation/cm** \\ \hline \multirow{6}{*}{Oblique cutting 1} & 1 & 2.31 & 1.8 & 30 & 5 \\  & 2 & 2.35 & 1.8 & 27 & 6 \\  & 3 & 2.43 & 1.9 & 20 & 3 \\  & 4 & 2.59 & 1.8 & 15 & 5 \\  & 5 & 2.65 & 2.0 & 10 & 10 \\  & 1 & 2.52 & 1.6 & 28 & 8 \\  & 2 & 2.68 & 1.7 & 18 & 0 \\ Oblique cutting 2 & 3 & 2.55 & 1.8 & 20 & 5 \\  & 4 & 2.76 & 1.9 & 14 & 9 \\  & 5 & 2.87 & 1.8 & 10 & 7 \\  & 1 & 2.36 & 2.2 & 20 & 6 \\  & 2 & 2.40 & 2.2 & 15 & 2 \\ Combined long and & 3 & 2.46 & 2.3 & 13 & 0 \\ short hole cutting & 4 & 2.51 & 2.5 & 8 & 8 \\  & 5 & 2.55 & 2.4 & 8 & 0 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Summary of actual parameters and effects of blasting tests.