Polar Division, Norilsk Nickel, Norilsk, Russia:

R. B. Galaov, Deputy Director in Mineral-Raw Materials Management, andreevaiv@tf.nk.nornik.ru
A. A. Kisel, Head of Geodynamic Safety Department

VNIMI, Saint-Petersburg, Russia:
A. A. Andreev, Head of Norilsk Sector
V. V. Zubkov, Chief Researcher, Doctor of Engineering Sciences

Skalistaya mine field lies northwards Komsomoslky mine fi eld and is a part of the Talnakh copper-nickel sulfide ore deposit. Geomechanics of enclosing rock mass of ore body S-2 is governed by adjacency of Norilsk-Kharaelakh fault and sub-parallel dip-slips, sub-meridional strike-and-dip slips and reverse faults, is characterized by steep dip angles of these dislocations and conditions considerable level of damage and, thus, low stability of ore body and enclosing rocks. Moreover, S-2 ore body is rockbursthazardous; for this reason, mining safety requires a package of rockburst prediction and prevention measures, and stoping is carried out in safety zones due to relaxation drilling. Aimed at efficient rockburst prevention planning, a ring of core holes was dilled from development drives in order to define stress tensor of initial rock mass unaffected by stoping. The borehole data were used to ensure safety of primary cutting. Considering predominant horizontal stresses oriented across stoping axis, after driving a stope drift, it was recommended to implement local rockburst-hazard prediction based on core disking and drilling data in the drift roof per each 20 m of blasting. Stress assessment showed nonhazardous level of stresses, and no special actions to prevent from rockbursting were required. As stoping was advanced, stresses in ore body under mining were assessed by mathematical modeling using SUIT3D. The modeling yielded that at the early stage of S-2 ore body mining, increased rock pressure zone was to extend up to 5 m around the stoping while stresses reached the value of 1.4γН. At this stage of mining, visual and instrumental (geophysical and geomechanical) monitoring of rock pressure near S-2 ore body showed no rock pressure events in advanced development drives with the undercut span 78 m long, and stresses were under 0.55 of uniaxial compression limit of ore, which was nonhazardous category of rockburst hazard rating.

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