RMZ – MATERIALI IN GEOOKOLJE

Physicotechnical substantiation of parameters of blasting operations in deep ...399is 1.10–1.25 kg/m 3 (Nobelan 2080), inwatered blastholes it is 1.15–1.30 kg/m 3(Nobilit 2030); stemming space lengthis 5–6 m. In the rock area of the openpit mine it is possible to apply the 250mm diam. blasthole network havingsize of 6.5 m × 6.5 m at specific BEconsumption of 0.98–1.05 kg/m 3 andstemming space length of 5.5–6.5 m.The developed parameters of DBOadapted to EBE have enabled to reduceexpenditures for blasting by 15 %with the best handling of the rock solidalong the whole height of the blastedbench.Development of effective blasting techniquesenabling to improve quality ofrock mass breaking and to enhancecompleteness of extraction of commercialmineral. Intensification of geomechanicaleffects with increasing miningdepth has impact on achieving the targetquality of breaking. This imposesfurther requirements to explosive ruptureof rock which are implemented bymeans of new methods and parameters.Researches on quality of rock massbreaking have demonstrated that evenobserving the determined optimal parametersof charge placing in the solidand at increased specific EBE consumption(q): on average for Nobelan1.11 kg/m 3 (maximum value is 1.27kg/m 3 ); and for Nobelit 1.26 kg/m 3(maximum value is 1.59 kg/m 3 ) it isimpossible to avoid yield of oversizeand coarse size. Moreover, at q ≥ 1.15–1.20 kg/m 3 as a result of predominanceof throwing (propellent) effect of anexplosion over rending effect a considerableportion of rock mass is thrownfrom the side of mined-out area (10–20%) on lower horizons or formation ofshotpiles as wide as up to 40 m takesplace. In the first case this results indecrease of quality and amount of ore,and in the second case this causes dropin intensity of mining operations.In this regard, researches have beenconducted to increase duration ofexplosion effect on the upper part ofbench and to enhance stemming efficiency.Specifically, to increase durationof explosion effect on the solidmass and to enhance locking effect itis recommended to use dynamic stemmingconsisting in explosion of BEcharge in an additional short blastholedrilled at 2 m distance off the mainblasthole or explosion of lockingcharge in stemming space of the mainblasthole. NTS was used to initiate BEcharges: in blastholes by nonelectricexplosion initiating device-B (blasthole)with delay of 500 ms; the surfacenetwork was arranged by nonelectricexplosion initiating device-S (surface)with delays of (25, 42 and 67) ms. Onexperimental areas the delays were selectedin such a manner that the lockingcharge was the first to explodeand then the main (primary) chargeexploded. Retardation of the mainRMZ-M&G 2012, 59