Abstract:Purpose: As the mining depth decreases, the reserves of ore in Daye iron mine gradually decrease. The effective way to solve the problems of large engineering quantity and high investment in deep mining development is to carry out the combination mining of the －450 m and －540 m levels. The feasibility and safety of high-level combination mining by filling method need to be explored and studied. To ensure the safety and efficiency of high-stage combination mining in Daye iron mine, based on engineering geological conditions and rock mass quality classification results, a study on optimization of structural parameters of high-stage combination mining in Daye iron mine was carried out. Method: On the basis of using the calculation method of the maximum unsupported span of the stope based on Q system rock mass classification and the introduction of ore and rock quality indexes, the maximum allowable safety span value of the stope can be calculated after analyzing the mining safety requirements and section size of each roadway of the mine and reasonably determining the corresponding stope structure parameters. In view of the impact of high-stage combination mining disturbance on the overlying rock formation, FLAC3D simulation software was used to conduct numerical simulation research on three schemes with stope heights of 105 m, 120 m, and 135 m. The displacement change values and stress distribution patterns of the stope roof and floor under different mining schemes were obtained. Result: When the stage height does not exceed 120 m, the maximum displacement occurs in the middle of the roof and floor plates and the deformation is small, resulting in less plastic damage areas, which can ensure safe mining of the mine. When the stope height reaches 135 m, tensile stress appears on both sides of the cement tailing backfill, and the displacement of the filling on both sides of the stope is large, exceeding the stope stability. Conclusion: The results show that: 1) Combined with the "Calculation of Maximum Unsupported Span of Stopes for Q System Rock Mass Classification" method and comprehensively considering the influence of factors such as rock mass integrity, joint characteristics, groundwater, and ground stress, the limit span of high-stage combination mining in Daye iron mine is determined to be 20 m. 2) Based on the FLAC3D numerical simulation software, a comparative analysis of the stress field, displacement field, and plastic zone before and after one-step mining and two-step mining of the three stope stage heights was conducted, and it was determined that the stope height should not exceed 120 m. Significance: The research results are expected to provide a basis for the optimization of reasonable stope structure parameters for safe high-stage combination mining of Daye iron mine, and provide a reference for the design of stope structure parameters for high-stage mining of similar mines at home and abroad.