Study On Synergetic Mining And Application In Transition From Open Pit To Underground Mining

About 90% of the open-pit iron mines in our country are going deeper, and most of them are gradually or have transferred into underground mining. Due to narrow space, during the period of transition, the production interference problems of them has not been well solved for many years, causing poor safety production conditions and lower product yield. Many mining had to reduce or stop production during this period, restricting the economic development of mining enterprises.Based on the research results and summary of experience from open pit to underground production, this paper analyses the inadaptability of the traditional mode of the transition that of reserved boundary pillars isolating underground and open-pit stope on the deposits efficient mining, thus offering a improved method which allows for synergistic mining the boundary pillars in the open and underground deposit. Also, this paper creates a transition mode of wedge transfer production by the method of underground induction caving to mine the hanging wall ore, mining pit ore during transition period, and explores the detail methods of synergistic mining including layout of underground induced engineering on the hanging wall ore body and method for determining the parameters of induced caving, the principles and detail optimization method for deep mining boundary in the open pit, the measures to ensure the safety of production and efficient mining technology etc. What’s more, according to mining index and extraction conditions of the optimal scheme of the mining, the detail optimization method of open pit and underground mining boundary is determined in the underground ore block unit, which is to control the induced engineering stoping sequence and gob height; using this method, the slope mining rocks move towards the surface collapse pit instead of falling into the pit. Besides, some other kinds of theory and technology are discussed including synergistic arrangements of mining sequence, synergistic drainage, synergistic form of the overburden, synergistic arrangement of development system and synergistic optimization of capacity management etc. thus a completely collaborative mining method is put forward. The method has been applied in Hainan Iron Mine, and in accordance with the deposit condition, further research was done on advanced and efficient mining technology on hanging wall ore body, three dimensional exploration and mining combination technology on the complex ore body, controlling method of high and steep rock slope movement, simple method of forming coating and so on; thus, more mining time of open pit and underground and higher underground production capacity growth rate had been achieved, and the difficulty about the production stable convergence was effectively solved during transition period from open pit to underground.Theoretical analysis and practical application show that the proposed synergistic method during the period of transition from open pit to underground mining overcomes mutual temporal and spatial interference between open-pit and underground mining brought by traditional ways, eliminating rock movement and landslide by mining, making effective use of technology advantages of them, considered as a new approach that has simple process, safety production conditions, high mining intensity and efficiency. The method is suitable for mining of metal mines under various stability conditions from open pit into underground. And it also can greatly improve the efficiency of the mining and increase production and keep safe during the transition period.