State Company Navoi Mining and Metallurgy Combine, Navoi, Uzbekistan:

N. P. Snitka, Chief Engineer

Navoi State Mining University, Navoi, Uzbekistan:
I. T. Misliboev, Assistant Professor, Candidate of Pedagogical Sciences

It is known that large-scale blasting both affects rocks inside and outside rock mass limits. It is suggested to use this effect to reduce cost of drilling and blasting in the pre-blasting weakening zones in rocks. The proposed method runs the following procedure. A block is divided into two portions along the width of a pass. The first (bigger) portion is drilled starting from the slope based on the standard design, the second portion (last row of boreholes) is drilled with enlarged spacing and the delay time for this row is expanded by 10 ms. The efficiency of the proposed process flow diagram of drilling-and-blasting has been proved experimentally, in three series of test explosions in open pit mines at Ziadin limestone deposit, Uzbekistan Railways. Each series of explosions practiced different number of blastholes (68, 87 and 96), diameters of blastholes (125, 125 and 214 mm), weights of explosive charges (85, 85 and 252 kg) and pre-blasting patterns (3.5×4, 4×4 and 6.5×7 m). For the comparison with the common technology, the check areas were delineated for the standard design drilling-and-blasting. The tests demonstrated feasibility of 20–25% wider spaced blasthole pattern and 10–15% lower powder factor with no essential enlargement of blasted rock fragments. Open pit mines that carry out blasting using the new technology have achieved appreciable economic effect.

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