Polar Division, Norilsk Nickel, Norilsk, Russia:

T. P. Darbinyan, Deputy Head of Mining Department, ggu@tf.nk.nornik.ru
N. K. Tukhvatullin, Leading Specialist, Geodynamic Safety Center
Yu. B. Sidorenko, Leading Specialist, Geodynamic Safety Center

Interregional Technological Department, Rostekhnadzor Federal Environmental, Industrial and Nuclear Supervision Service of Russia, Norilsk, Russia:
A. S. Koretskiy, Governmental Inspector

The Komsomolskaya Mine project provides for slice longwall with cemented backfi lling for the ore body named Tsentralnaya Osnovnaya. Aiming to improve the mine safety and to enhance its output, as well as to reduce ore loss, the technical services of the mine decided on a pilot trial of room-and-pillar mining method. If the thickness of the associated high-grade cupriferous ore occurrence is more than 7 m, the room-and pillar mining schemes condition separate extraction of different type ore (the first stage is extraction of high-grade cupriferous ore, the second stage is mining of fi nely disseminated ore); if the ore thickness is less than 7 m, it is recommended to carry out single-stage room-and-pillar. The ground control and safety of development and preparatory drives and rooms involve a package of measures, including instrumental measurement, visual observation and analysis of technological parameters of the mining method. Formation of safety zones for stoping in the area of the pilot trial involves destressing drilling to the depth of 4 m in sidewalls of preparatory drives on the upper and lower horizons. The research findings have exhibited increased stresses at a level higher than 0.7σ_com at a distance of more than 1.5 m from the stoping perimeter, which falls within the rockburst unhazard category. At the same time, visual observation in the northern stopes of the Tsentralnaya Osnovnaya ore body discovers traces of ground pressure events: growth of acoustic noise in the form of sharp rattle and dry clicking; condition of the preparatory drives has altered — the sidewall perimeter deforms, which is reflective of increased vertical stresses. In view of the discovered signs of higher overburden pressure, it is concluded on inefficiency of the destressing holes to relax stresses. To ensure geodynamic safety of stoping in the area of the pilot trial, it was decided to change the stress relaxation technique and to replace the destressing drilling from preparatory drives by formation of safety zones by relief hole drilling.

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