# Study on Airflow Field Distribution and Dust Distribution Characteristics at Blast Piles
## 3 Results and Discussion
### Analysis of Dust Generation Characteristics and Particle Size Distribution from Blast Piles
Observing the frequency distribution curve in the graph, PM2.5 (2.5-micrometer Particulate Matter, d = 2.5 \(\upmu\)m) has a very low frequency and is low in content. Respiable dust (d < 5 \(\upmu\)m) has a frequency of approximately 0.2, while PM10 (10-micrometer Particulate Matter, d = 10 \(\upmu\)m) has the highest frequency. The frequency of PM10-PM100 particles is roughly around 0.6. Overall, the cumulative distribution of medium and large particle sizes accounts for a relatively high proportion, reaching approximately 82%. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Particle Size**} & **Cumulative** & **Cumulative** & **Particle Size** & **Frequency** & **Frequency** \\  & **Distribution Q/\%** & **Distribution Q/\%** & **Xm/\(\upmu\)m** & **Distribution Q** & **Distribution Q** \\  & **(First Experiment)** & **(Second Experiment)** & **(First Experiment)** & **(Second Experiment)** \\ \hline
2.07 & 0.00 & 0.00 & 1.46 & 0.0  
Sphericity is a physical quantity that characterizes the similarity of a particle's shape to a spherical particle. A higher value indicates a greater similarity to a spherical particle. When dust particles move through the air, they encounter resistance, and the resistance coefficient is related to the sphericity. A higher sphericity leads to a smaller resistance coefficient, resulting in less resistance on the particle and facilitating its movement. From the sphericity distribution graph in Figure 8, it can be observed that particles with a diameter of less than 20 \(\upmu\)m have a sphericity value above 0.85, while particles with a diameter ranging from 20 to 150 \(\upmu\)m have a sphericity value above 0.75. Overall, the dust particles exhibit relatively high sphericity values, indicating that the dust is more prone to dispersion. various working platforms on the dumping side in Figure 9, there are small-scale swirls around them, indicating that there are small-scale vortices generated at these platforms, which is highly unfavorable for dust dispersion. However, when air enters from the mining side, the leeward slope has a gentle gradient, and in Figure 10, the velocity vectors are relatively smooth and evenly distributed throughout the open-pit mine, indicating that the airflow is not obstructed during its movement, which is beneficial for dust dispersion. It is also found that regardless of whether the air enters from the dumping side or the mining side, there are large-scale vortices generated at the bottom of the mine pit, where dust tends to accumulate and stay for a long time. This issue should be taken into serious consideration when conducting dust prevention and control measures at the blasting pile of the open-pit mine. To provide a more detailed analysis of the airflow distribution at the blasting pile in the open-pit mine under the two wind directions, the flow fields at the blasting pile were calculated for both the dumping side and mining side inlet conditions at different wind speeds (1, 9, 17 m/s). As seen in Figure 11, when the air enters from the dumping side, the dumping side with a steeper gradient becomes the leeward slope, and the mining side with a shallower gradient becomes the windward slope. As the wind speed gradient changes, there are significant variations in the airflow at the blasting pile platform on the leeward slope compared to that on the windward slope. However, when the air enters from the mining side, the dumping side with a steeper gradient becomes the windward slope, and the mining side with a shallower gradient becomes the leeward slope. The airflow patterns at the blasting pile platform on the leeward slope and the windward slope remain largely consistent and do not change significantly with the variation in wind speed gradient. This indicates that the wind direction has a significant impact on the airflow distribution in the open-pit mine.