Institute of Mining, Ural Branch, Russian Academy of Sciences, Ekaterinburg, Russia:

V. L. Yakovlev, Chief Researcher, Corresponding Member of the Russian Academy of Sciences, Professor, Doctor of Engineering Sciences, yakovlev@igduran.ru
I. V. Sokolov, Head of Underground Geotechnology Laboratory, Doctor of Engineering Sciences
G. G. Sakantsev, Senior Researcher, Underground Geotechnology Laboratory, Doctor of Engineering Sciences

Division of the Institute of Mining, Ural Branch, Russian Academy of Sciences, Chelyabinsk, Russia:
I. L. Kravchuk, Director, Doctor of Engineering Sciences

As open pit mining of deep complex-structure deposits comes to an end, it is becomes necessary to transit to underground method. The transition involves some technological and administrative actions aimed at the most effi cient conversion of a mine to another sequence and system of mining, and united under the notion of a transition process. The issues of open/underground transition are sufficiently covered in scientific and technical literature but the theory of transition processes has many weakly studied aspects, including terminology. This article gives definitions for transition process, transition period and mining sequence. Scenarios of mineral mining in pitwalls and under the pit bottom are proposed. It is found that the most difficult processes are connected with the creation of transition zones at the border between an open pit and an underground mine; development of the transition zones uses another technology than is in use in the stable operation period of a mine. It is suggested to assess efficiency of a transition process using the economic index of minimum reduction in annual profi tability of a mine in the transition period. This index is assessed in terms of Tarynnakh iron ore deposit in Yakutia. It is found that the recommended scenario will allow accomplishment of the transition period 4 years sooner than in the alternative scenario.
The studies used the research findings obtained in the framework of the competitive basic research project of the Ural Branch of the Russian Academy of Sciences in 2015–2017, Project No. 15-11-5-7. The authors highly appreciate participation of A. G. Zhuravlev and V. A. Yakovlev, researchers of the Institute of Mining, UB RAS, in these studies.

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