## 5 Conclusions  
In this study, based on the Jenike shear test principle, we designed a raw coal shear test system and utilized it to conduct tests on coal under different conditions, obtaining the variation patterns of raw coal adhesion properties. Employing the obtained parameters and the PFC2D software, we simulated and analyzed the coal flow characteristics, bunker wall pressure changes, and adhesive clogging characteristics during the discharge process of coal bunkers under different conditions, and the following main conclusions were drawn:1. The raw coal adhesion properties under different moisture contents, compaction forces, and shear interface conditions were obtained using the raw coal shear test. The results demonstrate that as the moisture content and compaction force of raw coal increase, the cohesion and internal friction angle at both the coal-coal and coal-wall interfaces exhibit an increasing trend. After the raw coal moisture content reaches 3%, its influence on the internal friction angle of the two interfaces diminishes. Beyond a moisture content of 3%, the internal friction angle was less affected by moisture. Beyond a compaction force of 400 kPa, the cohesion and internal friction angle at the coal-wall interface decreased. At the same moisture and compaction conditions, the coal-wall interface adhesion parameters exceeded those at the coal-coal interface, indicating a higher tendency for coal particles to adhere to bunker walls.
2. During bunker discharge, when \(\alpha<60^{\circ}\), the coal particles inside the coal bunker exhibit central flow characteristics, with high wall pressure and significant residual adhesive coal after discharge. When \(\alpha>60^{\circ}\), the adhesive coal inside the coal bunker is further reduced, but the coal flow rate during discharge is relatively high, making related control difficult. At \(\alpha=60^{\circ}\), the adhesive coal is significantly reduced, the coal flow rate inside the bunker is stable, and the wall pressure is moderate, making this value more suitable for underground coal bunkers.
3. When the moisture content \(w\) is relatively low, the coal material exhibits good flowability. As \(w\) increases, the adhesion properties of the coal material gradually strengthen, and the proportion of adhesive coal inside the bunker significantly increases. After \(w\) reaches 3%, the amount of adhesive coal in the coal bunker increases more than threefold compared to lower \(w\) values, the coal flow pattern transitions from mass flow to central flow, and the wall pressure increases. When \(w\) further increases, severe arching blockage occurs inside the coal bunker. Hence, controlling the moisture content of the coal material can improve its flowability and effectively reduce the risk of adhesive clogging.
4. As bunker storage height \(h\) increased, compaction force and adhesion strength of coal material rose, decreasing flow rate, increasing dynamic wall pressure peaks, and significantly raising the mass proportion of adhesive coal. When \(h\) exceeds 7 m, the coal bunker is highly prone to arched clogging. Hence, a more scientific and reasonable coal storage height planning can help reduce the contact forces between coal particles or between coal particles and the bunker wall, thereby decreasing the probability of adhesive clogging.  
Conceptualization, C.J. and L.W.; methodology, L.W.; software, Z.P.; validation, S.W.; formal analysis, C.J. and J.G.; data curation, C.J.; writing--original draft preparation, C.J.; visualization, C.J. and Z.P. All authors have read and agreed to the published version of the manuscript.  
This research was funded by National Natural Science Foundation of China (No. 52404070) and Natural Science Research Project of Anhui Educational Committee (No. 2024 AH050352).  
Not applicable.  
The data used to support the findings of this study are included within the article.  
The authors declare no competing interests.