Materiały konferencyjne SEP 1992

Szkoła Eksploatacji Podziemnej * 92 465 concentrated near to the face. Obviously this event zone correlates włth the zone of high stresses induced ahead of the face, which moves together with the face-advance (about 5 m/day) and produces smali bursts in the coal. When all of the events are localized for the whole retreat- mined area, they can also be plotter as an "event-density". which means number of events, located within a smali, limited area (e.g. 10 x 10 m). The result is shown in figurę 16, together with the locations of distresslng-blastings, which łndicate "critically" stressed zones, found by the results of test- drillings. As the count-rate correlates strongly with the face- advance, this effect dominates the plot. Within the first 15 weeks of mining with the highest advELnce, the event-rate or event-concentration also reaches the biggest values and it decreases generałly in the following phases with lower face- advance. Yet out of this generał effect there are some local specialities. For example we find relative maxima of the event- density before and behind the residual pi 1lar (dashed 1 ine in figurę 16), which was situated some 165 m above the mined seam. These concentrat ions also seem to correlate with stress- concentrations found by test-dri11ings and indicated here by destressing-blastings. Out of these pos i t i ve hi nts, the pl ot of the event-dens i ty shows some principal limitations too. For example the probe- distribution leads to a higher detection sensitłvity ahead of the middle of the face compared to the areas near both roadways. This and other disadyaintages can yet be overcome by calcułating also the energy release for the seismoacoustic events. The first results of such trials are very promising, so that it łooks like the seismoacoust ical method really provides a continuousły working watch-over-system in complement to the test-dri11ing method, which should improve the prevention of coal-outbursts. Literaturę 1. Betriebsempfehlungen: Empfehlungen zur Gebirgsschlagverhutung Ed. Steinkohlenbergbauverein. Bd.21, Essen. Gluckauf- Verłag, 1981.