## 4 Full-Scale Blasting Experiment
### Evaluation of Rock Fragmentation  
Muck piles of fragmented rocks were photographed using a single camera from the top surface of the bench and the front. In the images, a reference scale was used for single-scale factor analysis by applying a square marker target of 18 cm in width and height. Table 4 shows the image-based sieving analysis results of the rock fragmentation of the muck pile after full-scale bench blasting. Figures 12-15 show the analysis of the rock fragment size distribution. Larger rock fragments are displayed in red in the resulting image.  
Images taken from the top of the bench muck pile are compared. In the bench region to which sand stemming was applied, the characteristic size (\(X_{c}\)) for evaluating the fragment size is approximately 2.7 times larger than that in the region to which STF-based stemming material was applied. Moreover, the uniformity index (\(n\)) for evaluating the particle size distribution of the fragment rocks of the muck pile is 1.66 for the sand stemming region and 1.93 for the STF-based stemming. A higher uniformity index indicates a more uniform distribution of the fragmented rock.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Location from Which** & **Stemming Type** & **Characteristic Size** & **Uniformity Index** & **Average Fragment** & **Maximum Fragment** \\  & & **(\(X_{c}\), mm)** & **(\(n\))** & **Size (\(X_{0}\), mm)** & **(\(X_{m}\), mm)** \\ \hline Top of rock pile & Sand & 1149 & 1.66 & 836 & 1910 \\  & STF & 419 & 1.93 & 345 & 1.100 \\ Front of rock pile & Sand & 1234 & 2.07 & 1020 & 2610 \\  & STF & 938 & 2.01 & 772 & 2010 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Results of rock fragmentation analysis.  
Figure 11: Bench blasting results obtained by applying different stemming materials.  
Similarly, images taken from the front of the bench muck pile are compared. In the bench region to which sand stemming was applied, the characteristic size (\(X_{c}\)) for evaluating the fragment size is approximately 1.3 times larger than that of the region to which the STF-based stemming material was applied; however, the uniformity index shows no significant difference between the two cases. This is expected to affect the uniformity index as a large rock fragment falls to the front of the muck pile after blasting. These large fragments fell from the top of the outermost bench and had relatively little effect on the explosive force. Moreover, it is for this reason that the average fragment size compared, respectively, at the front and top of the bench muck pile image shows a significant difference  
The WipFrag 3 program automatically generates the histogram graph. The x-axis is a log graph showing the size distribution of the rock fragments. The y-axis is the rate of passing. Large fragments are marked with boxes in Figures 12-15. The size of the large fragments that must be subjected to secondary breaking with a breaker machine before being placed in the jaw crusher line is approximately 1000 mm or more in diameter. When STF is applied as a stemming, the average fragment size decreases, and the number of large fragments that require second breaking work is greatly reduced.  
Figure 12: Rock pile image, contouring, histogram, and cumulative size curve of the fragmented block (bench top image of sand stemming case after blasting).  
Figure 14: _Cont._  
Figure 13: Rock pile image, contouring, histogram, and cumulative size curve of the fragmented block (bench top image of STF stemming case after blasting).