## 6 Conclusions  
This study focuses on optimizing the charge structure to achieve separate mining in coal and rock mixed blasting. Based on coal and rock blasting crater tests, the energy distribution law during coal and rock mixed blasting was analyzed. The throwing process and damage characteristics of coal and rock blasting under different charge structures were studied through numerical simulations. In addition, field mixed blasting separate mining experiments were conducted using the optimized charge structure. The following conclusions are drawn:  
1. A characteristic curve of the coal bench blasting crater is established based on the results of on-site blasting crater tests. When the ratio of charge length to stemming length in coal and rock bench blasting exceeds 0.91 and 0.74, respectively, the internal crushing effect of the rock mass is enhanced, and the utilization rate of explosive energy in coal and rock fragmentation gradually surpasses that in rock casting.
2. The numerical results of coal and rock mixed blasting indicate that when the bottom spacing length of the rock bench is 2 m, and the stemming length of the coal seam ranges from 2.5 to 3 m, the distribution of explosive energy within the rock mass near the stratified interface is optimized, enhancing the rational utilization of energy, facilitating the connectivity of rock damage cracks, and improving the tension cracks' distribution at the coal seam's top. In addition, no bulging or coal-rock interaction (explosive mixing) phenomenon occurs at the coal-rock interface, and the blasting effect satisfies the requirements of mixed separate mining.  
Figure 18: Blasting test results.  
3. The coal and rock mixed blasting test results indicate that a reasonable charge structure is one of the key factors in achieving coal and rock mixed blasting separate mining. After optimizing the charge structure, the cast blasting distance of the rock bench ranges from 21.65 to 32.59 m. The crushing effect of Scheme 1 at the stratified interface is superior to that of Scheme 2; however, both schemes meet the requirements of separation and crushing. These results demonstrate that the optimized charge structure effectively fulfills the purpose and requirements of coal and rock mixed blasting separate mining.  
Conceptualization, A.J., H.F. and Y.L.; methodology, A.J., Y.L. and Y.Y.; software, A.J.; validation, Y.Y. and S.B.; formal analysis, A.J., Y.Y. and J.G.; investigation, Y.L.; resources, Y.L. and H.F.; data curation, A.J., H.F. and Y.L.; writing--original draft preparation, A.J., H.F. and Y.L.; writing--review and editing, A.J., H.F., Y.Y. and S.B.; visualization, A.J. and S.B.; supervision, H.F. and Y.Y.; project administration, Y.Y.; funding acquisition, H.F. and Y.Y. All authors have read and agreed to the published version of the manuscript.  
The study is supported by The National Natural Science Foundation of China (Grant No. 52208477) and the Collaborative Innovation Center for Major Disasters Prevention and Restoration in Mines (Grant No. CXZX-2024-07), which are gratefully acknowledged.  
Not applicable.  
The data presented in this study are available on request from the corresponding author; due to the fact that the data will also be utilized in the preparation of a dissertation, they cannot be publicly disclosed.  
The authors declare no conflicts of interest.