Study Of The Best Mining Mode For The Transferring From Open-pit Mining Into Underground Mining In Shirengou Iron Mine

Currently, more than85percent of Iron ore resources in China are open-pit mining. After decades of mining and constantly increasing production, most of the domestic open-pit mining enterprises are facing the issue of closing the open-pit mining and about to switch to the underground mining stage. In view of the characteristics that the open-pit mining enterprises in China mostly are of the furrow open-pit mine, more difficulties will be faced in the underground mining. To achieve the smooth transition of the open-pit mining to the underground mining, the key technologies must be studied, and coordinating the safe and efficient mining technology is one of the focuses of the research. In this article, though the means of site investigation, comprehensive analysis, program designing and optimization, analog analysis and mathematical analysis methods, systematical and in-depth study of the transition exporation system from open-pit to underground in Shirengou iron mine, the mining method in the transitional stage and the transition mode and made the following findings:(1)In order to ensure the compact transition, sustained and stable production, the method Shirengou iron ore used is feasible, which the open-pit part was ended in phases, the underground part was constructed and producted in phases, but the period of the service, engineering had been put into, was short. The utilization rate was low and the transition from open-pit mining to underground mining is lack of overall planning of improvment.(2)For the problem how to make full use of the original main shaft and auxiliary shaft and how to minimize the transformation as much as possible, three programs were proposed that tunneling a new auxiliary shaft, transforming and extending the auxiliary shaft and tunneling a new blind shaft, and they were compared in technical and economic aspects, finally, the program tunneling a new auxiliary shaft was recommend. (3)After a comprehensive technical and economic analysis, the explore program using the main and auxiliary shaft combined with the auxiliary ramp was recommended for the transition from open-pit mining to underground mining.(4)Though evaluating the mode of transition from open-pit mining to underground mining, the following conclusions were presented:the production capacity was low in transition period, and the integrated capacity of the deposit was used in a low level. When combined open-pit and underground, the contact was in a low degree, lacking of uniform and comprehensive planning. In addition, the transition period was shot, the space contact was relatively close, however, because the transition time was not efficient, and the security pillars in the open-pit bottom realm were set aside, which made the integration of the development and mining technology in the open-pit mining and underground mining was in a low degree.(5) Counting the body thickness and dip by category, we can know that, the thick and heavy ore-bodies accounted for more than90%, inclinations of which are inclined or steeply inclined. The mining methods can be used such as sublevel rock drilling and stage room stoping, sublevel caving, the upward horizontal slicing and filling method and open-stope succeed by filling method and so on. To meet the needs of production management and security technology management, for the mining conditions, by the fuzzy mathematical methods to optimize the choice, obtaining the most optimal mining method of Shirengou iron ore for the transition from open-pit mining to underground mining:sublevel rock drilling and stage room succeed by fill method.