Relevance. At present, during the transition from open pit to underground mining at iron ore deposits, the most widespread technology is the sublevel caving with frontal ore drawing. This technology has significant drawbacks, namely low ore extraction indicators and increased operating costs for preparatory work and stoping. The development of an alternative technology for the upper sublevel mining, which ensures high extraction indicators, active ore drawing, and lower prime cost of the main flow processes in the presence of an internal dump used as a rock cushion on the quarry floor, is an urgent scientific and technical task.
Research objective is to study the mining factors effect on the technical and economic indicators of differing technologies for mining the upper sublevel under the rock cushion at the iron ore deposits.
Research methods. The work uses a comprehensive research method, including the search and design of a rational version of technology, economic and mathematical modeling, and technical and economic comparison. Analysis of the results. The dependences of the main technical and economic indicators (losses and dilution, the specific volume of preparatory development works, labor productivity and specific operating costs for flow processes) on the height of the upper sublevel between 40 and 100 m and mine capacity between 0.8 and 2.4 million tonnes of ore per year. It has been determined that the operating costs for ore mining have a minimum value under a height of the upper sublevel of 80 m and a production capacity of 1.6 million tonnes of ore per year, which is optimal for an enterprise during the transition period.
Conclusions. The technology of sublevel open stoping with the subsequent rib pillar development by a system of induced block caving has been substantiated, which far more efficient as compared to the traditional version of sublevel caving.

Keywords: iron ore deposit; transition zone; rock cushion; mining system; mining factors; extraction indicators; technical and economic indicators.

Acknowledgements. The research has been carried out within the framework of the state contract no. 075-00581-19-00, theme no. 0405-2019-0005.

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