Dynamic Control Technology Of Safe And Efficient Mining Transition From From Open-pit To Underground Mining

With the rapid economic development of the high demand for resources and the restrict conditions of mineral resources exploitation, many open pit mine are turning to underground mining. During the period of transition open pit to underground, there are many issues:such as how to join the production and develop systems in open-pit to underground, how to keep steady supply of ore production, how to set up boundary pillar between open pit bottom and underground mining, how to assurance the stability of the open pit slope and so on. Therefore, study on technique of safe and efficient mining in smooth transition from open-pit to underground mine, and find a reasonable methods and means in transition from open pit to underground mining is an important issue of open pit mine production, safety management restructuring, achieve sustainable development in mining.The paper based on issues of safely and efficiently technology in transition open pit to underground mining in Shandong Gold Mining Guilaizhuang Co., Ltd. through analysis the mining engineering geology, reserves and production and the status of mining, using the methods of numerical simulation and theoretical analysis. Studied on the effect of stability of the slope and boundary pillar during the mining of the transition from open pit to underground, design optimization of boundary pillar and stoping, underground mining stoping sequence and the first stratified choice, technology of extending not expand the slope, technology of mining slope ore, develop engineering and convergence of production capacity during the transition period as well as flood prevention and drainage, underground ventilation and other safety exploitation of key technical issues. Providing technical support for the continuity capacity and achieve safe and efficient mining of underground stopes in transition from the open-pit to underground mining. Details are as follows:(1) Through on-site research on Guilaizhuang gold mine, Comprehensive analysis of the deposits geological conditions, mining conditions, geological reserves. Based on the theory of strength reduction, using the finite element software FLAC3D made a numerical simulation study on the effect of the slope stability in the open pit extend mining and side slope mining in Guilaizhuang. Based on the results of numerical analysis, combined the open slope joints survey and the actual district situation, proposing the specific techniques and methods of slope reinforcement.(2) Proposed the new model of embedded composite structure made of artificial boundary pillar. Using artificial bottom and concrete composite backfill structure, through partitioning, hierarchical and step by step excavation, forming a complete embedded artificial boundary pillar with the rocks of hanging wall and foot wall. Improved the overall stability of the boundary pillar, prevented the open pit catchment penetration effectively and ensure the safety of underground mining production. Achieved safe and efficient boundary pillar mining from open pit to underground mining, solve the technical problems of formation of boundary pillar from open pit to underground.(3) Proposed a efficient mining method of combining open and underground, under the conditions of without stripping rock from bottom of open pit, making use of development of open system, using techniques of underground mining access fill stoping, achieved safe and efficient mining of boundary pillar from open pit to underground mining, ore recovery reaches95%, effectively easing the capacity convergence problems during transition period.(4) By optimizing the stoping process and structure parameters, proposed a smooth transition technology program on open-pit to underground production. Use the ramps as the main transport system in the transition period. According to the status underground development and boundary pillar formation process, make full use of existing projects to determine the first stratified, underground mining method and stoping sequence,technology of extending not expand the slope, technology of recovery slope ore, maximum adapted to time and space coordination during the transition period of the open pit to underground mining. Achieved smooth transition and safe and efficient production of capacity in Guilaizhuang gold mine from open pit to underground mining.(5) Considering the ventilation and drainage problems that exist in Guilaizhuang gold mine, optimized the mine ventilation and drainage system, improving the safe operation conditions for transition from open pit to underground mining.