# Research Progress and Typical Case of Open-Pit to Underground Mining in China
## 4 Conclusions  
As shallow resources are depleted and stripping ratios continue to rise, the transition from open-pit to underground mining has become a critical strategy for ensuring the sustainable development of large-scale metal mining operations. This paper systematically reviews the current state of research on key technologies involved in the transition from open-pit to underground mining, and, based on the engineering practices at Xinqiao Mine, presents representative technical pathways and optimization strategies. The findings indicate that the following factors are essential for a successful transition:  
1. The transition from open-pit to underground mining necessitates a mine-specific, phased implementation approach. It is essential to choose an appropriate development system--whether independent, partially integrated, or fully integrated--based on geological conditions, resource depth, and production scale. The joint development system at Xinqiao Mine, which integrates a main and auxiliary shaft with a ramp, has successfully increased mining efficiency by 25% and reduced surface disturbance by 40%, confirming the model's effectiveness and environmental advantages under specific conditions. 2. The selection of mining methods directly impacts the success of the transition and the efficiency of resource recovery. Compared to stope mining and caving mining methods, backfilling mining offers distinct advantages in stabilizing surrounding rock structures, controlling surface subsidence, and enhancing resource recovery rates. As backfilling materials and techniques continue to evolve, their application in green mining construction becomes increasingly significant. Xinqiao Mine has adopted the upward horizontal layered backfilling method, achieving a recovery rate  
Figure 11: Tailings management and ecological restoration at Dongguanshan Copper Mine: (**a**) schematic diagram of the tailings solidification backfilling project for the Dongguanshan Copper Mine open pit; (**b**) site layout of the tailings transportation pipeline; (**c**) site view of the open-pit ecological restoration project. Source. All images adapted from [[[http://www.tlys.cn/index.aspx](http://www.tlys.cn/index.aspx)]([http://www.tlys.cn/index.aspx](http://www.tlys.cn/index.aspx))] (accessed on 9 July 2025). of 84.66% and a low dilution rate of 3.41%, while significantly reducing environmental disturbances. This demonstrates the comprehensive advantages of the method. 3. Slope stability control is essential for ensuring the safe operation of a mine throughout its lifecycle. During the transition from open-pit to underground mining, the original slope stability system faces rebalancing challenges due to stress redistribution and disturbances from mining activities. Existing research has developed several theories and models, including limit equilibrium analysis, numerical simulations, and physical modeling, providing a scientific basis for predicting slope behavior and disaster risks. However, the mechanisms of slope instability under multi-factor coupling conditions remain highly uncertain, necessitating further studies in multi-field coupling, time evolution, and system dynamics. 4. National-level green mining policies, especially the \"Zero Waste Mine\" initiative, have driven significant technological innovations in the mining sector, particularly in tailings backfilling and solid waste resource utilization. Tailings backfilling not only reduces tailings discharge but also facilitates the ecological restoration of closed pit land. Additionally, it enhances resource utilization efficiency and lowers energy consumption per unit of production. For example, Xinqiao Mine has successfully integrated solid waste resource utilization with environmental protection by utilizing tailings from the Dongguanshan Copper Mine for open-pit backfilling. This approach demonstrates both the feasibility and the exemplary role of green mining transformation.