Mining University of Kola Science Center of Russian Academy of Sciences (Apatity, Russia):

Fokin V. A., Leading Researcher, Doctor of Engineering Sciences, e-mail: fva666@goi.kolasc.net.ru

Kovdor Ore Dressing and Processing Enterprise (Kovdor, Russia):

Togunov M. B., Chief Specialist on Drilling and Blasting Operations
Semkin S. V., Chief Engineer of Mine
Shitov Yu. A., Deputy Chief Engineer on Drilling and Blasting Operations

Сrushing quality of blast rock mass is the main indicator of drilling and blasting operations’ efficiency under open-pit mining conditions. Thus, there are shown the following key parameters, characterizing the crushing quality:
-size of an average piece of rock;
-yield of fractions, which size exceeds maximum permissible value (oversize yield);
-yield of fractions, which size doesn't exceed the target value.
Regular measurements of granulometric structure of blast rock mass have the following peculiarities:
- provision of monitoring of the basic trends in crushing quality change;
- timely responding to quality degradation and estimation of new designs’ efficiency of charges or new types of explosives, compared to the previously used ones.
At the same time, comparison of crushing quality will be reliable in case of methodical uniformity in initial data obtaining on the foregoing crushing quality parameters. According to this, new and more informative criteria should be used. This makes it possible to reduce all possible options of block blasting (various types of explosives, different diameter and design of borehole charges) “to a common denominator”. For this purpose, the authors proposed the new criterion of crushing quality of blast rock mass and relevant scale of quality classification, based on this criterion. Thus, the horizontal axis of the scale can be different, depending on the purpose of the analysis: for example, specific energy of different type explosives (efficiency is analyzed by comparison of previously used and new explosives with same diameter of borehole charges and same initiation method); diameters of borehole charges (impact of charge diameter is analyzed for crushing efficiency under similar initiation method and same type of explosive); chronological dates (months and years, if chronological changes for a certain period of time are analyzed). Case studies of proposed technique are presented to make the crushing quality assessment of blast rock mass, using borehole charges of different diameters and initiation methods as well as some aspects of an average blast piece of rock, based on uniqueness of solution principle.