Improvement of the transitional technology from open pit to underground mining of magnetite quartzite

Abstract

The paper analyzes the disadvantages of the technology of iron ore open pit mining and current environmental problems of open pit mining. The paper also addresses problems of possible displacement and strains of rocks in the classical open pit mining method with extraction of minerals exclusively by open pit mining, studies current transitional technologies from open pit to integrated open pit-underground and subsequent underground mining, and presents an improved methodology for studying the stress-strain state of the massif during transition from open pit mining to integrated open pit-underground and subsequent underground mining. There are studied, developed and proposed options of environmentally friendly technologies of integrated open pit-underground mining with mining waste disposal in the worked-out space of underground mines and open pits, highly efficient calculation schemes for studying the stress-strain state of a rock massif during transition from open pit to underground mining with formation of protective barrier pillars, an option with the development of the lower room of stage II under protection of an ore pillar left within the contours of the upper room of stage I, and an option with the development of the lower room of stage II under protection of an artificial pillar made of the consolidating backfill in the upper room of stage I. The stress-strain state of the massif and possibilities of forming internal waste rock dumps when applying integrated open pit-underground mining technologies are studied and substantiated. Transition technologies from open pit to underground mining of iron ore raw materials under the bottom of an operating open pit are developed and proposed on the example of Kryvyi Rih iron ore basin.