Seismic and rock burst hazards still currently appear to be important in most hard coal mines in Poland. Recently, there has been a significant increase in seismic activity in the Silesian rock mass, in comparison to previous years. In the period 2001-2010, hard coal mines experienced 33 rock bursts. The causes of rock burst occurrences are here presented, based on an analysis of the rock bursts that occurred in Polish hard coal mines. The scale of the rock burst hazard has been characterized with respect to the mining and geological conditions of the existing exploitation. The most essential of the factors influencing the status of rock burst hazard is considered to be the depth of the interval, ranging from 550 m to 1150 m. The basic factors that cause rock burst to occur are as follows: seismogenic strata, edges and remnants, goafs, faults, pillars and excessive panelling. The consequences of rock bursts are damaged and/or destroyed roadways. On this basis, the areas (ranges) of safe zones were selected as being those safe from rock burst hazard in roadways, according to the assessment conducted to establish different degrees of the risk., Renata Patyńska., and Obsahuje bibliografii
This paper presents the relation between main crack systems and physical properties of carbonate rocks. The existence of cracks in a rock mass causes the reduction of seismic wave velocity, which is smaller in direction perpendicular to a crack plane than in direction parallel to it. This affects the occurrence of the anisotropy of seismic wave velocity, which is characteristic for rocks with preferred orientation of cracks. The existence of relationship between crack and seismic anisotropy allowed to use geophysical methods for determination of fracture density and orientation of crack systems. The research area is located in the south-east part of the Upper Silesian Trough. Tectonic observation and geophysical measurements was carried on the carbonate sequence on the both fold limbs building the Chrzanow-Wilkoszyn Syncline, originated during the Early Cimmerian movements, in the Upper Triassic - Middle Jurassic period. It was measured seismic waves velocity in the surface layers of rock mass and the strike azimuth and dip angle of cracks.The seismic anisotropy of the rock mass was done along radial profiles having common central point using P.A.S.I. Seis mograph (Mod.16S24-N). Results of field measurements were interpreted to estimate components of crack and velocity tensors. Obtained outcomes allowed to compare the existing main crack systems on the both fold limbs with seismic measurements. Eventually we have shown that seismic measurements are useful tool to study the cracks anisotropy in rocks inaccessible for direct observations., Iwona Stan-Kleczek, Katarzyna Sutkowska, Dominika Stan and Mikołaj Zolich., and Obsahuje bibliografické odkazy