Mining Institute, Kola Science Center, Russian Academy of Sciences, Apatity, Russia:

S. A. Kozyrev, Head of Laboratory, Doctor of Engineering Sciences, skozirev@goi.kolasc.net.ru

Kirovsk Branch Apatit, Kirovsk, Russia:
A. Yu. Abrashitov, Director
V. S. Onuprienko, Chief Engineer
A. V. Volkov, Head of Drilling-and-Blasting Department

The paper reveals the main factors affecting the quality of ore fragmentation in underground mines of the Kola Peninsula, and suggests engineering solutions to improve efficiency of blasting in sublevel caving method using emulsion explosives. Based on the revealed patterns of emulsion matrix gasification, the optimum detonation characteristics of the emulsion explosives, as well as charging, initiation and blasting parameters were determined. The actual energy characteristics were evaluated for Sabtek explosive in various diameter boreholes, and, thereupon, blasting patterns were designed for different types of ores and rocks of the Khibiny Massif. It is shown that according to the conditions of borehole damage under explosive impact, deviation in drilling, and charging conditions, the borehole depth should be no more than 20–25 m. This allowed justification of the blasting perimeter and drilling pattern for rhomb-shaped excavation panels in underground mines of the Kirovsk Branch Apatit. It is shown that electronic drilling charts allow shorter preparation period, more accurate drilling path as compared to manual drilling and reduced probability of damage to boreholes under blasting. The optimal delay interval has been substantiated theoretically for nonsimultaneous blasting of boreholes in a fan. It has been established that the maximum breaking of rocks between boreholes occurs when the blasting delay is 15 ms. The effectiveness of the optimal delay intervals was estimated based on the fragmentation quality and blast-induced load of nonsimultaneous blasting at delay intervals of 10, 15 and 20 ms in the Rasvumchorr mine. It is shown that with 20 ms delay interval, the distinct periods are observed between blasts as compared with delay intervals of 10 and 15 ms. Furthermore, the seismic-induced load on nearby excavations reduces, and fragmentation is improved. The indicated delay interval was recommended for ore breaking in underground mines of the KB Apatit, which improved blasting safety and efficiency.

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