Abstract
In accordance with the formal regulations currently in force in Poland, the criteria for rockburst hazard assessment with respect to coal deposits include the records of seismic events and their impacts, de-stressing of the entire seam or its parts and expert opinions of mine operation engineers. Effectiveness of the de-stressing can be verified by geophysical test data whilst the expert opinions are mostly based on mathematical modelling using specialist software or dedicated simulation algorithms. This study collates and synthesises the results of tests carried out in a seam section in a colliery within the Upper Silesia Coal Basin, obtained by the outlined methods. Geophysical survey results are interpreted basing on seismic tomography procedures utilising the geo-tomography techniques for velocity field reconstruction in data processing. For comparison, the stress state modelling data are provided, based on conventional engineering solutions applicable to mechanics of deformable media. The actual assessment of the rockburst threat level is based on observations of distributions of the longitudinal wave velocity in relation to the actual value of the vertical component of stress concentration within the coal seam.
Highlights
Mining operation in the conditions of rockburst hazard require effective prevention measures, including long-term and short-term control strategies developed in the mining practice [1]
With reference to the geological and mining conditions in the area, the study synthesises the key aspects involved in the development of the state of stress and the de-stressing effects experienced during mining operations in one of the collieries in the Upper Silesia Coal Basin
The main objective of the investigations was to compare the geophysical survey data with analytical results obtained by the methods of strata mechanics in the context of rockburst hazard assessment prior to projected mining operations
Summary
Mining operation in the conditions of rockburst hazard require effective prevention measures, including long-term and short-term control strategies developed in the mining practice [1]. The stress relief effect consists in reduction of the stress tensor components within the seam being mined, whilst the destructive effect gives rise to formation of the cracking and fracturing zones within the deposit such that it is no longer able to accumulate elastic energy. The conditions prevailing in a plot in the coal deposit (shortwall panel AD/510) to be mined in one of the collieries within the former Katowice Mining Holding S.A. are investigated and used in the comparative study of the rockburst threat levels derived by geophysical methods [12] and analytical simulations [13]. Geophysical methods include seismic tomography with the technique of P-wave velocity field reconstruction whilst analytical modelling relies on conventional studies of the state of stress in rock strata affected by the presence of old exploited mine workings, recalling the principles of mechanics of elastic media [14,15,16]
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