## 6 Discussion  
As previously mentioned, existing research on extraction zone morphology has predominantly employed experimental and numerical simulations based on single-hole ore discharge configurations, typically yielding inverted droplet-shaped or ellipsoidal extraction zones. Crucially, the inclination angle of the drawbell in the block caving method is not consistent in the direction parallel to and perpendicular to the laneway. In this scheme, the inclination angle parallel to the laneway direction is \(90^{\circ}\), and the angle perpendicular to the laneway direction is \(70^{\circ}\). Higher inclination angles correlate with increased ore flow  
Figure 28: Moving surface of the fifth-layer monitoring points under different particle gradations.  
rates, and this directional flow differential fundamentally generates elliptical extraction zone cross-sections, a finding that markedly contrasts with prior results and conclusively demonstrates the profound influence of drawbell geometry on extraction zone contours. At the same time, in the block caving method, the bottom structure typically incorporates multiple drawbells arranged systematically. When these drawbacks operate concurrently, their respective extraction zones progressively expand with increasing draw height, leading to gradual convergence and overlap between adjacent zones. Research has demonstrated that overlapping extraction zones between neighboring drawbells are essential for maintaining uniform ore release rates and mitigating ore dilution during production. Notably, the ore flow velocity correlates positively with the extent of this overlap, a critical factor in optimizing subsequent extraction drift layouts. This study employs a 1:66 similarity ratio for experimental modeling, when applied to the Pulang copper mine's bottom structure design at a draw height of 46.2 m, Gradation-I conditions yield maximal zone overlap, whereas Gradation-III exhibits minimal overlap due to larger rock fragmentation sizes. While these findings offer theoretical guidance for block caving infrastructure design, two key limitations warrant attention:  
1. The predefined angles of drawbell orientations (parallel/perpendicular to the lineway) directly influence inclination and directional ore flow velocities, thereby modifying extraction zone morphology.
2. Practical mining scenarios involve simultaneous multi-drawbell operations where drift spacing and lineway intervals dynamically alter overlap characteristics, and multi-drawbell simulations are planned as part of ongoing work.  
Investigation, H.L.; Resources, G.L.; Data curation, D.G. and R.G.; Writing--original draft, R.C.; Writing--review & editing, C.Y. All authors have read and agreed to the published version of the manuscript.  
This paper received its funding from projects (Nos. 52474118, 52104110, and 52004329) supported by the National Natural Science Foundation of China; Project (2023 JJ30666) supported by the Hunan Provincial Natural Science Foundation of China.  
Not applicable.  
Informed Consent Statement: Informed consent was obtained from all subjects involved in the study.  
The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.  
Authors [PERSON], [PERSON], [PERSON] were employed by Yunnan Diqing Non-Ferrous Metals Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.