## 4 Blasting Experiment
### Experimental Results
#### 4.3.2 Ejection Rate Analysis of the Stemming Material  
The study assessed how well each material resisted being ejected using a high-speed camera that took images every 0.82 ms. The time it took for the stem to be ejected was measured from when the detonation began and was observed through the ventilation hole. The results indicated that the ejection velocity decreased in the following sequence: \"Only Sand\", \"STF\", \"STF + Spike Plug + Sand\", and \"STF + Twist Plug + Sand\". Figure 11 displays the images captured by the camera, which recorded 1200 frames per second for analysis purposes. Based on the observed ejection resistance tendencies of stemming materials with a 1200 fps camera, a 5000 fps high-speed camera was utilized to calculate the ejection speed and momentum of the secondary stem ejected by the gas pressure. For the momentum calculations, the mass of the stemming component was set at 150 g. The analysis results from the 5000 fps high-speed camera are presented in Table 5, and Figure 12 displays the high-speed camera images used for the analysis. Figure 10: Waveform of the measured residual gas behavior. The time it took for the stemming to resist action was noted as 3, 3, 3, 3.5, and 3.8 ms for the scenarios involving \"Sand\", \"STF + Spike Plug + Sand\", and \"STF + Twist Plug + Sand\", respectively. By calculating the momentum loss towards the shock chamber entrance, based on these resistance times, it was found that using \"STF + Sand\" resulted in a 7.5% enhancement in blockage performance compared to scenarios with sand as the stemming material. A lower momentum value indicates a better resistance performance of the stemming material. Moreover, an improvement in blockage performance was observed with the use of STF stemming material along with a plug device. Specifically, employing a plug led to a blockage enhancement of around 1.28 times compared to using sand for stemming. Finally, the histograms shown in Figure 13 illustrate ejection velocity, momentum per unit mass of stemming material, and relative blockage performance analyzed based on ejection time for each scenario involving stemming materials. Figure 11: Images from the 1200 fps high-speed camera used for the analysis. (**a**) Sand, (**b**) STF, (**c**) STF + spike plug + sand, and (**d**) STF + twist plug + sand. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{\begin{tabular}{c} **Stemming** \\ **Material** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Resistance Time** \\ **(ms)** \\ \end{tabular} } & \multicolumn{2}{c}{\begin{tabular}{c} **Terminal Ejecting** \\ **Velocity** \\ **(m/s)** \\ \end{tabular} } & \multicolumn{2}{c}{\
\begin{tabular}{c} **Momentum** \\ **(N-s)** \\ \end{tabular} } & \multicolumn{2}{c}{
\begin{tabular}{c} **Relative Blockage** \\ **Performance** \\ **(\%)** \\ \end{tabular} } \\ \hline Only Sand & 3.0 & 100 & 13.5 & 100.0 \\ STF + Sand & 3.2 & 93 & 12.5 & 107.5 \\ STF + Spike Plug + Sand & 3.6 & 83 & 11.2 & 120.4 \\ STF + Twist Plug + Sand & 3.8 & 77 & 10.5 & 130.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Results of the stemming material ejection rate analysis. Figure 12: Images from the 5000 fps high-speed camera used for the analysis. (**a**) Sand, (**b**) STF, (**c**) STF + spike plug + sand, and (**d**) STF + twist plug + sand. The speed at which the stemming material is pushed out of the blasting hole decreased as the gas pressure resistance of the material increased. Among types of stemming materials tested, \"STF + Twist Plug + Sand\" showed an ejection rate that was 0.8 ms slower than the regular sand stem. Its resistance performance improved by 30% in terms of momentum. The analysis revealed that all stemming materials exhibited the following order of ejection resistance: \"Sand\", \"STF + Sand\", \"STF + Spike Plug + Sand\", and \"STF + Twist Plug + Sand\".