Dynamic Influence of Near-Source Seismic Ground Motion on Underground Mine Working Stability Using Time-Frequency Analysis

Peak particle velocity parameter is very useful in assessing underground mine working stability. Its application is widespread and requires additional analysis of the dominant frequency of the seismic signal. In order to properly analyze the velocity amplitudes of strong ground motions generated from seismic sources, time-frequency properties of near-source seismic signals in underground mines should be quantified. Using numerical calculations, the continuous wavelet transform (CWT) of the recorded near-source seismic signals in three perpendicular directions was obtained to characterize its time-frequency properties. The properties of recorded strong ground motion velocity seismograms for two high energy seismic events and two blasts from two underground coal mines in Poland have been extracted with the use of continuous wavelet transform spectrograms showing the duration time of each frequency group. Assuming a constant peak particle velocity amplitude on the analyzed seismograms, the duration time of each frequency group starts to play a key role. The longer the duration time of the lower frequency group is on the CWT spectrogram, the more the damaging effect on underground mining excavations can be observed. Varying bandwidths of dominant frequencies in separate time intervals for the analyzed seismic signals have had significantly different influence on the potentially damaging effect on underground mining excavations.

Optimization of Parameters to Improve Ventilationin Underground Mine Working using CFD

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Classification of Theories about Rock Pressure

The first classificationsw of physical properties of rocks and hypotheses of rock pressure in the world practice are analysed. The analysis of internationally widely known theories about rock pressure and physical processes around mine workings is executed. Classification of theories about rock pressure on classification feature “condition of investigated massif” is constructed. The energy theory that describing capsulation by the massif of underground mine working is offered.

APPLICATION OF OTT'S MINE COORDINATE SYSTEM IN THE PAST AND IN PRESENT DAY

The coal district system of coordinates for mines located in the Ostrava region was established in 1858 by Dipl. Ing. František Ott, Surveyor of the Emperor Ferdinand Northern Railway (Severní dráha Ferdinandova). Coordinates of all significant points of existing mine shafts, characteristic mine surface points, and points in terrain, were determined by establishing mine triangulation within the Western part of the Ostrava-Karviná Coal District (OKR) on an area comprising almost 58 km2. Said points were stabilized by granite stones. The reason to establish this system of coordinates was to determine the points of a uniform basis of coordinates for making surveys both on the mine surface, i.e. for connecting the underground mine working, and simultaneously for removing any discrepancies occurring with respect to mine boundaries among particular proprietors, i.e. to allow for exact demarcation of mine areas bestowed to them by the state. Thus, nowadays Ott's system of coordinates that used to be applied during the period, in which within the OKR redevelopment works took place, like abatement the coal mining consequences.