Mining Institute, Kola Science Center, Russian Academy of Sciences, Apatity, Russia:

I. E. Semenova, Leading Researcher, Candidate of Engineering Sciences, innas@goi.kolasc.net.ru

This article presents a scientific approach to the solution of geomechanical problems arising in mining of closely spaced ore deposits under high tectonic stresses. The approach has been developed at the Mining Institute of the Kola Science Center, RAS. The article gives a case-study of the Khibiny massif subjected to simultaneous mining of seven apatite–nepheline deposits under conditions of rockburst hazard. The author proposes geomechanical justification for the joint opencast and underground mining operations based on the 3D modeling of the stress–strain behavior of rock mass, including generation of a package of different-scale finite element models, starting from the scale of an ore field and down to certain geotechnical elements. The justification procedure includes:
- geomechanical transformation assessment in rock mass under large-scale parallel excavation of reserves from closely spaced deposits and determination of mutual influence zone of the opencast and underground mining fronts;
- development of a procedure and algorithms for the formation of a package of geomechanical numerical models to assess geological and geotechnical effects on the stress–strain behavior of rock mass on different scales;
- studies of deformation and failure of undermined rocks under prevailing horizontal compression;
- development of the geomechanical supervision principles for mining operations in closely spaced ore deposits under conditions of rockburst hazard.
The study was carried within an R&D project, including Topic No. 0226-2019-0058, and was supported by Apatit’s Kirovsk Division and by the North-Western Phosphorus Company. The results were included in the updated guidance documents and regulations for mining operations in ore bodies, on horizons and at interfaces in the Khibiny apatite arc.

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