Abstract
This paper presents the results of seismic profiling along the sidewalls of two headings of a longwall in a coal-seam at a depth of about 850 and 870 metres in a coal mine in the Upper Silesian Coal Basin, Poland. The seismic profiles were located in a zone of impact of the same overlying edge of the coal-seam located about 40 m above. This study was interesting from that point of view since there were no other geological and mining factors present which could disturb the impact of the coal seam edge. The profiling of refracted P-wave velocity changes was carried out according to the Dubinski method. This method is used for the assessment of relative stress in a coal seam in the side wall of the excavation. The results obtained on both seismic profiles are very similar, which demonstrates the small impact of the overlying edge of the coal seam in both headings of a longwall. It should be emphasised that at greater exploitation depths, the calculated reference velocity is less reliable than the measured reference velocity. Presumably, the method of calculating seismic anomaly requires updating under such conditions, but additional evidence should be collected.
Highlights
In underground coal mines, various types of hazards occur which affect the maintenance of the stability of excavations which are related to geological and mining factors [1,2,3,4]
Assuming that on the initial section of the profile, measured wave velocities P are not disturbed by an edge influence and other geological and mining factors, it can be assumed that the measured reference velocity is 2220 m/s
Under the conditions of multi-seam exploitation in underground coal mines, excavations are often located in the zone of excessive impact of various types of edges and remnants of unexploited coal seams
Summary
Various types of hazards occur which affect the maintenance of the stability of excavations which are related to geological and mining factors [1,2,3,4]. Such hazards include various edges and remnants of already-exploited coal seams, which create excessive concentrations of stress in the rock mass and a simultaneously unfavourable impact on mining excavations [5,6]. The results achieved by seismic profiling are useful in qualitative assessments of the stability of supportexcavation systems and rock bursts
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