Geotekhnologia Research and Technology Center, Chelyabinsk, Russia:

V. A. Pikalov, Head of a department, Doctor of Engineering Sciences, pikalov@ustup.ru
A. V. Sokolovsky, Chairman of the Board of Directors, Doctor of Engineering Sciences

SUEK-Kuzbass Company, Leninsk-Kuznetsky, Russia:
V. N. Vasilets, Principal Engineer, Open Pit Mine Management

Magnitogorsk State Technical University, Magnitogorsk, Russia:
K. V. Burmistrov, Assistant Professor, Candidate of Engineering Sciences

The article describes a procedure of determining efficient interrelated parameters of hybrid open pit/underground coal mining to ensure mine safety enhancement and coal production increment at the concurrent operation of open pit and underground mines in complicated deeper level geological and mining conditions. It has been found that as against sequential transition from open pit to underground mining, concurrent hybrid mining is complicated by negative cross-influence of the methods. The basic negative factors of the concurrent hybrid open pit and underground mining is seismic effect of large-scale blasts in open pit onto stability of underground excavations and generation of a subsidence trough, which initiates such hazardous geomechanical events as cracks, funnels, sinks and horizontal displacements in open pit. The hybrid coal mining flow sheets are classified based on the criterion of position and advance of the open pit and underground mining fronts relative to each other; the mathematical calculations based on these classifications are built-up for: geomechanically safe spacing of production faces in open pit and underground mines; rate of approach of open pit and underground mining fronts for various orientations of the fronts; parameters of suspending open pit mine sections on approach of the open pit and underground mining fronts and duration of the period of suspension conditions and time for a suspended section to reach the normal operating conditions after resumption of work. For estimation of production conditions in hybrid open pit/underground mines, it is suggested to use the work mix coefficient as the product of the suspended mining front length and the suspension time. In this case, the production is optimized due to withdrawal of the suspended mining front length and the suspension time, i.e. the target function of short-term and long-term mine planning is reaching zero value of the work mix coefficient.

The authors appreciate contribution of V. Yu. Zalyadnov, Candidate of Engineering Sciences, Assistant Professor at the Open Pit Mineral Mining Department, Magnitogorsk State Technical University.

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