Drill-and-Blast Pattern Adjustment for Mining Conditions at Open Pit Coal Mines in Permafrost Zone in Russia’s Far East
Al. A. Galim’yanov, V. I. Mishnev
Institute of Mining, Far Eastern Branch, Russian Academy of Sciences, Khabarovsk, Russia
Keywords: Permafrost zone, borehole charges, charge cavity volume, interpermafrost water, borehole wall caving, blast-induced damage factors, liquid emulsion explosive, blasting block volume
Abstract
The problems connected with the adjustment of drill-and-blast patterns for the volume change in a charge cavity in case of deformation of borehole walls in case of drilling in open pit coal mining in the permafrost zone in Russia’s Far East are justified. The examples show that in drilling on benches 10 and 15 m high, 2-17% of boreholes require redrilling because of partial disintegration of rocks beyond the hole perimeter and due to caving of rocks inside the holes. In case of redrilling, the drill-and-blast patterns undergo decrease in the borehole spacing, which leads to the increase in the range of hazards in terms of the damage factors (flyrock and seismic impact). Borehole wall caving changes the charge cavity volume, which affects the quality of liquid emulsion explosive charges in mechanical pumping. A set of devices is proposed for the charge decoupling to ensure stability of the explosive charge cavity under conditions of large block blasting at mineral deposits situated in the zones of discontinuous permafrost.
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