Browsing by Subject "seismic source parameters"

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Access status: Open Access ,
An attempt to determine the cause of the strong tremor responsible for a rockburst in a hard coal mine based on numerical modeling and spectral parameters
(Wydawnictwa AGH, 2024) Wojtecki, Łukasz; Krawiec, Krzysztof; Ćwiękała, Mateusz; Dzik, Grażyna
Seismic and rockburst hazards represent significant challenges during the longwall mining of coal seams. One analytical approach to assess the potential for rockburst hazards involves reconstructing the stress conditions within the rock mass. This article reports on the findings from three-dimensional (3D) numerical modeling aimed at examining the distribution of maximum shear stress within the rock mass amid the longwall mining operations of the 703/1 coal seam in a mine situated in the Upper Silesian Coal Basin, Poland which was disrupted by a rockburst incident. On the day of the rockburst, substantial concentrations of maximum shear stress were identified in a thick sandstone layer proximate to the boundary of the overlying 624 coal seam located significantly above the 703/1 coal seam. The calculated maximum shear stress demonstrated an increase of approximately 80% over the values observed in the absence of edge effects. Furthermore, also higher concentration of maximum shear stress was identified within the geologically weaker strata adjacent to the 703/1 coal seam. These observations facilitated the classification of the examined rockburst as a stress-stroke phenomenon. Additionally, the study determined the spectral parameters of the tremor, which possessed an energy of 9.8 × 10$^{7}$ J and triggered the analyzed rockburst. The ratio of the seismic energy of S and P-waves confirmed a shear mechanism in the focus. The scope of inelastic deformation within the focal zone was also quantified. Following the event, the rock mass that had been destressed due to the significant tremor and subsequent rockburst exhibited reduced seismic activity upon the resumption of longwall mining of the 703/1 coal seam.
Access status: Open Access ,
Ocena zagrożenia tąpaniami w kopalniach podziemnych uwzględniająca parametry drgań blisko ognisk wstrząsów - doświadczenia z polskich kopalń
(2007) Mutke, Grzegorz
To study the rockburst hazard and underground mine working stability it is essential to know not only the static loads but also the dynamic loads. The performed analysis of the effects of mine tremors from the Upper Silesian Coal Basin, and of their intensity and various types of damage, clearly shows that they only occurred when the tremor sources were located close to the openings (mostly up to 100 m). These observations show that the ground motions parameters at such distances may be crucial for the occurrence of a rockburst because the high values of the PPV parameter are proportional to high dynamic stresses and underground hazards. An empirical criterion for potential rockburst hazard has been developed based on the worked out correlation dependences. In analyzing the documented database of 120 rockbursts from the Upper Silesian Coal Basin that occurred during a period from 1988 to 2006, the above mentioned criterion was verified. It has been found, that 90% of the rockbursts occurred in the area where peak particle velocity (PPV) reached values ranging from 0,05 m/s to 1 m/s. The investigation results presented in this this paper may be used in both the spatial and time table planning of mining operations under predicted high seismicity conditions and the rational choice of support and preventive actions ensuring functionality of mine workings and improvement in work safety level.