Materiały konferencyjne SEP 1992

428 Underground Exploitation School '92 of the evaluation, a seam or a part of it is classified as dangerous or not from the point of view of the possibłe release of a rock burst. Criteria based on the theory ajid also on the practice of bursts occurred in the Basin were set for it. The prediction is madę already at the stage of exploratlon of the deposit and is continued throughout the life of a given mine working. The degree of danger of a rock burst release is predicted at the stage of designing the face or the roadway. Its position in « relation to other openings in the ssane seam and in the adjacent seams is considered in the prediction. Three degrees are being recognized. The third one is the most dangerous. Dur i ng t he life of the faces and roadways, the yield of chippings from especially driven borehołes is measured. The dia- meter of these borehołes is 42, 115 or 200 mm. The borehołes of 115 and 200 mm diameter are mainly used during the roadways dri- ving because they are simultaneously considered as distressing borehołes and they assure the prediction of one day of advance of a roadvra.y driven by cont inuous miners. The frequency and intensity of seismoacoustic impulses (the noise of rock mass) is monitored simultaneously with the drilling using a transportable device. In such a way» prediction of real danger of a rock burst at a given site is raade. A network of seismological stations on the surface and un- derground has been built in OKD to make space prediction of rock bursts. Recently a seismic polygon has been also built to improve this prediction. Some mines were equipped with stationary seismoacoustic apparatuses to record seismoacoustic activity during the mining. The impulses are monitored continu- ously. They are a manifestation of deformations produced in rock mass by the effect of brittle fracture accompanying changes in the stress-strain condition of the mass induced by the mining. The above methods are also used to check the effectivity of preventive measures taken against the danger of rock bursts. Dur i ng the 1as t two years some new methods of rock bursts prediction have been łnvestigated by the research institute VVU=^ in Ostrava in Coal Mine Czechoslovak Army. The results of this