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

A. D. Sashurin, Geomechanics Research Manager, Chief Researcher, Professor, Doctor of Engineering Sciences, sashour@igd.uran.ru
A. A. Panzhin, Academic Secretary, Candidate of Engineering Sciences
Yu. P. Konovalova, Researcher
N. A. Panzhina, Junior Researcher

Hybrid opencast/underground mining enables high production performance. In the unified mineral resources development strategy, the hybrid method has essential advantages in terms of resource saving and energy efficiency. On the other hand, combination of the opencast and underground operations at the same object initiates some geomechanical problems which, if treated improperly, often imperil further exploitation. The major mutual influence of the opencast and underground mining operations shows itself by way of formation of stresses and strains in rock mass. Stress state essentially complicates stability of basic structural elements in hybrid opencast/underground mines, including pit walls, and permanent, development or breakage headings. Depending on composition of rocks, high concentration of stresses can greatly increase rockburst hazard in separate rock mass areas. Moreover, the influence of stress state is not limited to initiation of local instabilities. In practice of large-scale opencast/underground mining, it is known that some hazardous geodynamic process can be identified as induced earthquakes which damage mine infrastructure and bring other disastrous consequences. In this connection, implementation of the advantages of the hybrid mining technology calls for the comprehensive solution of geomechanical problems. This article considers the long-term experimental studies of stress state at the Vysokogorskoe iron ore deposit subjected to different variants of large-scale hybrid mining for nearly 300 years.
The study has been supported under State Contract No. 007-01398-17-00, Theme No. 0405-2015-0012.

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