Belgorod National University, Belgorod, Russia:

I. M. Ignatenko, Director of the Institute of Earths Sciences, Candidate of Engineering Sciences, ignatenko_i@bsu.edu.ru

VIOGEM, Belgorod, Russia:
E. B. Yanitsky, Deputy CEO in Research and Development, Candidate of Geologo-Mineralogical Sciences
V. A. Dunaev, Professor, Doctor of Geologo-Mineralogical Sciences
S. G. Kabelko, Leading Researcher, Candidate of Engineering Sciences

In open pit mining, the critical factor of pitwall stability and blastability is jointing of exposed rock mass. This article, in terms of the open pit at the Zhelezny mine of Kovdor Mining and Processing Plant, shows variability in jointing intensity laterally and vertically in rock mass under development. Moreover, it is found that lithologically uniform sites are composed of both low and heavily jointed rocks at the same depth, due to the spatial variability of tectonic stress field intensity. This implies weak dependence of jointing on petrographic type of rocks and, accordingly, advisability of annual estimation of jointing in pitwall rock massIt is found that heavy jointing reduces strength of rocks, which is especially observable in jointing category II rock mass, as a result of weaker cohesion between mineral particles and due to formation of microcracks under the action of tectonic stresses. Considering exponential dependence of average block size on depth and the approximating function of this dependence, the graph of behavior of average block size with depth is plotted in the size range from 0.22 to 1.19 m in the depth interval of 0–150 m and to 1.4 m at the depth of 450 m.

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