## 6 Conclusions  
Based on the FLAC 3D numerical simulation platform, the Mohr-Coulomb plasticity criterion is used to simulate the caved body, the strain-softening criterion is used to simulate the affected rock mass, and a three-dimensional numerical analysis model is established to study the stability of rock mass during the open-pit-to-underground mining process based on the full consideration of caved body migration factors. This provides a methodological reference for the analysis of rock stability in open-pit to underground mines. The following conclusions were obtained:  
1. After mining at the 0 m level, the stress concentration in the rock mass around the recovery area is obvious, and a 30-40 m wide stress concentration zone is formed between the E2-E9 profiles of the north gang and the east gang, and the subsequent mining stress is mainly concentrated in the north side of the recovery area and gradually develops toward the E11 profile. When mining reaches the \(-\)240 m level, the stress is concentrated in the surrounding area of E9 and E11 profiles, and the stress concentration around the south mining area is significant.
2. The development direction of the caved zone changes with the ore body's storage conditions, mainly to the east, with less influence on the stability of the west gang rock. After the end of mining at a \(-\)60 m level, the caved zone mainly develops in the area west of E9, and, from \(-\)120 m onwards, the caved zone is mainly located in Beiyi East. Under the influence of the distribution of the caved zone, the east gang of the open pit and the surrounding rock masses are displaced toward the bottom of the open pit, while the west gang rock masses are not affected by the caved zone. When mining from a +30 m to 0 m level, the range of surface subsidence zone is small, and after mining at a \(-\)120 m level, the range of subsidence increases rapidly, covering the whole pit bottom area and expanding to the east, south, and north, forming a large mining disturbance area.
3. At the end of mining to the 30 m level in the Beiyi quarry, the mining disturbance caused the foot of the east gang slope to sink. The overall rock body was destabilized, resulting in a large-scale landslide toward the bottom of the open pit, and the simulation results matched the actual situation. In a future production process, the mine should also continue to pay attention to the development of landslides in the east gang of the open pit and the stability of the rock body of the central side slope of the south gang and the local side gang of the north gang.  
Figure 11: In situ observation of collapse of the eastern area of Beiyi mining area.  
**Author Contributions:** [PERSON]: in situ investigation, data analysis, writing--original draft, and writing--review and editing. C.M.: numerical modeling and data analysis. [PERSON] performed the numerical analysis on slope stability evaluation. [PERSON] revised the manuscript and summarized the work content. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This work was financially supported by the National Natural Science Foundation of China (52074020) and the Interdisciplinary Research Project for Young Teachers of USTB (Fundamental Research Funds for the Central Universities) (FRF-IDRY-21-001).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The data will be available under request.  
**Acknowledgments:** We thank [PERSON], [PERSON], and [PERSON] for their contibution in the experimental study of this work.  
**Conflicts of Interest:** Author [PERSON] was employed by the company Hainan Mining Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be constructed as a potential conflict of interest.