Investigation On The Stability Of Boundary Pillar And Mining Technology In Transition Open-pit To Underground Mine

Mine shifting from open-pit to underground mining is a comman problem in most mines of China, especially in such mine as use openstope method to exploit the first bed orebody. The technical and safe problems include mine methods, the slope stability of open-pit, transition layer control, pillar recovery and gob management, the stability of stope structure, underground pressure, boundary pillar stability, preventing spontaneous caving and inrush, et al. All these problems must be analyzed, demonstration and make feasibility program before the mine shifting from open-pit to underground mining. The boundary pillar stability, preventing spontaneous caving and inrush are the key technical and safe problems. Boundary pillar instability, spontaneous caving and inrush can induce big disaster and economic losses. In this paper, study and analyses on boundary pillar stability and preventing spontaneous caving and inrush was carried out. Based on the result, feasibility program was established to instruct mining.If fault and crush belt existed in the mining zone, underground mining will meet bigger technical problems. The turbulence of underground mining and formation of gob will make fault and crush belt moving, avalanching and caving. Therefore, technical analysis and establish safety feasibility mining program must be carried out before exploitation in the areas with fault and crush belt. This paper aimed at mining method under fault and crush belt of Shi Rengou iron mine influence to make analysis and establish a safety, feasibility and reasonable mining technical program.Shi Rengou iron mine started shifting from open-pit to underground mining much earlier in china. In this mine, many technical problems were met in this process. These problems have big technical difficulty and are similar with other mines. So it has representation typical ness. Therefore, this paper had been included in the National 11th Five-year Technical Program.Boundary pillar stability, preventing spontaneous caving and inrush and mining technical under the influence of fault and crush can be deemed as problems as rock stability and deformation damage. There are many methods to solve rock stability. But the characteristics and factors considerate are different of these methods. Therefore, it is necessary to synthesis considerate these methods to supplement each other. Field physics mechanical property test, monitoring analysis, engineering analogy analysis, limiting equilibrium analytic, two dimension numerical simulation, three dimension numerical simulation were used synthesis in this paper to analyze boundary pillar stability, preventing spontaneous caving and inrush, and establish technical program under the influence of fault and crush. The mainly studies of this paper are following:1. Determined the structure characteristics and physics mechanical property in Shi Rengou iron mine;2. Determined the program of pillar thickness under different mining condition and established measure of preventing spontaneous caving and inrush in Shi Rengou iron mine;3. Study on the areas of rock deformation, boundary pillar caving and inrush under the influence of fault and crush in Shi Rengou iron mine;4. Subarea on stability of the shifting from open-pit to underground mining zone in Shi Rengou iron mine;5. Instruct underground mining and carried out field monitoring analysis and program adjusting to contract with the study result;6. Combination with the requirement of the Shi Rengou iron mine to establish safety and highly active mining program under fault and crush belts.In this paper, summarized the study method to which solve the key problem of the process of shifting from open-pit to underground mining. Put forward a set of scientific research ideas for the process of shifting from open-pit to underground mining. Formation of the stability analysis and research theory of surrounding rock may add rock mechanics theory.The analysis system and method of rock failure mentioned in this paper can analyze the evolution failure of rock destabilizing mechanics when the process of shifting from open-pit to underground mining. It supplies new visual analysis method for the rock destabilizing mechanics during the process of shifting from open-pit to underground mining.The research production applied in Shi Rengou iron mine for 3 years and. The application result approved it is valid. The disaster of boundary pillar caving and spontaneous caving and inrush had not occurred. Additional, because filed motoring and program adjusting, mineral resources have recovered maximally and create huge economic returns for Shi Rengou iron mine.