The analysis of rock bursts effects in Ostrava-Karvina Coalfield has indicated a principal difference between effects of rock bursts on gates and effects on longwall faces. The effects on gateways are distinctly more intense even if they occur at lower energy level of dynamic events. Mostly opened support structures in gateroads are concerned with relatively low resistance against dynamic loading from roadway side and floor (such load is most frequent in case of rockbursts). The proper reinforcing measures must include a reinforcing of steel support structure and influencing of phisico-mechanical characteristics of rocks and coal in roadway surroundings (reinforcement by grouting and bolting).


Hard coal extraction in Ostrava- Karvina coalfield (hereafter only OKR) which is part of Upper Silesian hard coal basin is accompanied by rock burst manifestations. The increasing number of rock bursts dates back mainly to seventies of XXieth and it is connected with advance of coal winning (especially In Karvina part of coalfield) into the area of thick coal seams (exceeding 2.5 m) with interseam positions formed by rigid sandstone strata and by layers of siltstones and conglomerates (Lower Sucha and Saddle strata of Upper Carboniferous, i.e. Middle and Upper Namurian).

Equally in course of the last fifteen years in connection with privatisation and restructuring of mining companies the coal mining conditions in OKR have changed conspicuously as a wind-up of coal production and reduction of coal output led to closure of all underground coal mines in Ostrava part of coalfield. he gravity centre of coal production moved then to Karvina area of coalfield and thus the share (but also quantity) of coal output from seams endangered by rock bursts increased. This is the reason why even at reduction of total coal output the rock bursts have been still intensely manifested.(see Fig. 1, Konecny et al 2003). By unfavourable impacts of underground rock bursts on domain of safety and health of miners and naturally also on cost sphere and on total coal production economy have necessitated a more detailed investigating of genesis and action of such dynamic events.

(Figure in full paper)

Figure 1. Development of coal output of OKC in million t/a structured into total coal output (TO), output of Karvina part of coalfield (KI), output of rock burst prone seams (RPS) compared with number of rockbursts (NR).


Analysing of genesis and effects of underground rock bursts based on performed measurements has enabled defining of the following two principal types of underground rock bursts. During the beginning phase (in seventies and eighties of XXieth century) so called in-scam rock bursts with a focus within coal seam in vicinity of affected mine working prevailed. They were manifested by brittle failure of coal seam adjacent to mine working being advanced with a minimum failure of roof rock or floor rock strata (so called shelf effect).

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