## 5 Conclusions  
In this study, we investigated the effects of new mining activities on the surface and the formation mechanisms of large-scale fractures on the southern side of the Prang Copper Mine's subsidence area. The following conclusions were drawn:  
1. The initiation of new mining activities in the southern part of the Prang Copper Mine's first mining area resulted in ongoing subsidence of the upper surface. Due to the complex interactions between surface and subsurface structures, the surface displacements exhibit non-uniform patterns. The numerical simulation results indicate that, during this process, surface rock layers near the subsidence area experience initial displacements with the highest magnitudes. This phenomenon is closely related to the subsidence of the pre-existing collapse zone. As the subsidence continues, it gradually extends southward, eventually reaching the pre-existing structural weaknesses on the slope surface, forming fractures that evolve into more giant fissures. The simulation results after 4000 steps of this numerical model run show that the top gap width reaches 0.6 m with a vertical offset of 1.8 m;  
Figure 15: Pictures of slope anchor failure on the west side of the drainage ditch.  
2. As mining-induced subsidence progresses, the internal structural weaknesses within the rock and soil gradually evolve into fractures and subsequently expand into large fissures. In real-world engineering environments, apart from the effects of subsidence, rainfall may expedite the softening of the rock and soil, further facilitating the expansion of these fissures. If appropriate mitigation measures are not implemented, these fissures could potentially lead to slope sliding and toppling, compromising the stability of underground and surface structures;
3. We observed a similar trend between the simulated and actual displacement curves by comparing the numerical simulation results with data from actual monitoring points. Based on the results of the numerical simulation and 1000 h of monitoring results before the site inspection, the displacement of the monitoring point after 1500 h was predicted to be 0.884-1.35 m in the Y direction, 0.42-0.688 m in the X direction, and \(-\)1.45-2.3 m in the Z direction, while the actual monitoring of the site for 1500 h showed that dy was 1.44 m, dx was 0.20 m, and dz was 1.29 m. This shows that the numerical model has some reference value.  
Conceptualization, Z.L. and K.H.; methodology, G.L. and J.T.; software, T.L.; validation, T.L.; formal analysis, J.T.; investigation, T.L.; resources, Z.L.; data curation, T.L. and G.L.; writing--original draft preparation, Z.L.; writing--review and editing, Z.L. and K.H.; visualization, T.L.; supervision, G.L.; project administration, J.T.; funding acquisition, G.L. All authors have read and agreed to the published version of the manuscript.  
This work was supported by the National Natural Science Foundation of China (No. 41974148); the Natural Resources Science and Technology Project of Hunan Province (Grant No. 2022-01); the Transportation Science and Technology Project of Hunan Province (No. 202217); the Science and Technology Research and Development Project of China Railway Co., Ltd. (No. 2022-Special-07-02).  
Not applicable.  
The data used to support the findings of the research are included in this article.  
Author [PERSON] was employed by the company Yunnan Diqin Nonferrous Metal 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. The authors declare that this study received funding from the Science and Technology Research and Development Project of China Railway Co., Ltd. The funder was not involved in the study design, collection, analysis, interpretation of data, the writing of this article or the decision to submit it for publication.