Destress blasting in deep mines of NorNickel’s Polar Division

Talnakh and Oktyabrsky ore fields are estimated as rockburst-hazardous starting from the depth of 700 m downward according to safety rules. This means that mining is only permitted within certain protected zones. At the present times, such protected zones are generated in underground mines by means of the large-diameter destressing drilling. Despite proved efficiency, the high cost and large amount of the destressing drilling are the grave faults of this approach. Aiming to save drilling cost, it is proposed to make rock mass rockburst-unhazardous using destress blasting. This article gives a brief description of the destress blasting mechanism. This method has been effectively used in relaxation of pillars from stresses before extraction of the reserves from the pillars both in Russia and abroad. In Oktyabrsky Mine stress relaxation of pillars was implemented by slotting, and the drilling and blasting data were available. This study proposes to destress rock masses by means of directional destress fracturing in horizontal plane through blasting of decked charges of special design. The initial parameters for destress blasting using holes with diameters of 76 and 130 mm are determined. The charge design aimed to ensure a zone of fractures in the horizontal plane, at minimized vertical fracturing is described. This information can be used in planning of full-scale tests to refine parameters and application ranges of the method. For the full-scale tests, it is suggested to undertake destress blasting at different blast patterns on different test sites, and to compare the results with the current destressing method (destressing drilling). Efficiency can be proved using geomechanical and geophysical methods. The authors appreciate participation of V. P. Marysyuk and T. P. Darbinyan from NorNickel’s Polar Division in this study.

Geomechanical characteristic of ventilation shaft VS-3 in Oktyabrsky mine during extraction of mineral reserves from protective pillar

The strain analysis procedure is discussed in terms of a vertical mine shaft under the impact of extraction of ore reserves from protective pillar in Oktyabrsky mine of NorNickel’s Polar Division. The procedure is used in predictive strain analysis in depth of the shaft in case of different scenarios of protective pillar mining in ventilation shaft No. 3. The calculations show impossibility of preservation of shaft VS-3. Based on the prediction, it was decided on the early analysis of ventilation alternatives in the mine without involvement of shaft VS-3. The implemented research saved significant assets from spending on the shaft maintenance in the period of extraction of ore reserves from the protective pillar. Moreover, the time allowance until disability of shaft VS-3 enables scheduled planning and construction of access gateways to ensure the required ventilation mode in the mine. The authors appreciate participation of D. A. Kotikov, S. Yu. Shilenko, V. V. Balandin, M. P. Sergunin, A. V. Kulov, V. N. Andreev and A. K. Ustinov in the study.