Institute of Mining, Far Eastern Branch, Russian Academy of Sciences, Khabarovsk, Russia

E. B. Shevkun, Chief Researcher, Professor, Doctor of Engineering Sciences, ev.shevkun@yandex.ru

E. N. Kazarina, Junior Researcher at Rock Fracture Sector

AVT-Amur LLC, Blagoveshchensk, Russia
A. Yu. Plotnikov, Deputy Chief Engineer of Drilling and Blasting, Candidate of Engineering Sciences
P. V. Nikulin, Managing Director, Malomir Mine

The current fleet of single bucket excavators at open pit mines in the Far East of Russia consists mostly of hydraulic machines with bucket capacity of 4–36 m³. Reliable operation of such machines is only possible at high-quality fragmentation of strong rocks by blasting. At the same time, in open pit mining of high-value ores in strong rock masses, it is required to preserve natural ore and waste rock interfaces to reduce mixing of rocks in disintegration during preparation of strong rocks for excavation using special blasting techniques. Therefore, for the last ten years, the authors engaged themselves in development of a technology of blasting-induced loosening at open pit mines of Atlas Mining Group. The technology was aimed to ensure high-quality fragmentation of rocks by blasting at maximum preservation of initial ore–rock interfaces to reduce ore dilution without escalation of material costs. High results are achieved with delays longer than 100 ms between successively blasted charges: the mechanism of explosive rupture of rocks in multi-row short-delay blasting changes drastically as such delays enable formation of screening (reflective) surface represented by earlier blasted rock mass, which essentially alters interaction between the stress wave energy and rocks. As a consequence, the blasting energy is maximally spent for rock loosening at the minimal displacement of blasted rock mass owing to control of parameters of the reflected and refracted stress waves in rock mass at the same charge energy, and the kinetic energy of ejection is redirected to rock fragmentation. It is shown that blasting at delays longer than 200 ms increases the yield of broken rocks at the essentially decreased powder factor. The pattern of blastholes with the diameter of 5 m is increased to 6.5×6.5 m, and the yield of broken rocks is expanded to 30 m³/m. As against the delay intervals of 150–200 ms, dilution is reduced from 8.8 to 7.6 %, and the loss of useful materials is decreased by 22%.
The authors would like to appreciate participation of S. I. Korneeva, Leading Researcher and Candidate of Engineering Sciences from the Institute of Mining, FEB RAS in this study.

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