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An attempt to determine the strong tremors causes during longwall mining of destressed bottom layer of a thick coal seam

Pakosz Rafał, Wojtecki Łukasz, Mendecki Maciej J., Krzyżanowska Agnieszka

Journal of Sustainable Mining

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2025

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Vol. 24, iss. 1

145--157

EN

The sequence and method of coal seam mining can significantly minimize the risk of rock bursts. The planning of exploitation in the Bielszowice part of the Ruda Hard Coal Mine involves maximizing the destress effect associated with the mining of adjacent coal seams or layers of thick coal seams. Longwall mining of destressed coal seams is characterized by much lower seismic activity; however, even during such mining, high-energy tremors may occur. This article analyzes the seismic activity accompanying the mining of longwall panels in the bottom and top layers of thick seam No. 510 and seam No. 507 in the Bielszowice part of the Ruda Hard Coal Mine. An attempt was made to determine the reasons for the occurrence of high- and medium-energy tremors during the longwall mining of the bottom layer of seam No. 510, which had been destressed by the earlier excavation of the top layer of this seam. For this purpose, the focal mechanisms of these tremors were calculated using the seismic moment tensor inversion method. In the foci of high-energy tremors, the shear mechanism was dominant. A correlation was found between the occurrence of high-energy tremors and the edges of previously mined coal seams.

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Identification of strong tremor causes for appropriate rock burst prevention in a hard coal mine

Pakosz Rafał, Wojtecki Łukasz, Mendecki Maciej J., Krzyżanowska Agnieszka

Journal of Sustainable Mining

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2024

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Vol. 23, iss. 2

132--146

EN

The exploitation carried out in the Bielszowice part of the Ruda Hard Coal Mine is mainly accompanied by seismic and rock burst hazards. The occurrence of high-energy tremors may be associated with many factors, e.g., fracturing of thick layers of high-strength rocks or destruction processes of a stressed and/or thick coal seam. These factors are often combined when excavating a single longwall panel. Determining the causes of strong tremors is of fundamental importance for mining and rock burst prevention. The extraction of the 004z longwall panel in the top layer of coal seam No. 504 was designed in complex geological and mining conditions. During the mining of the 004z longwall panel, strong tremors with energies of 105 J and 106 J occurred. The analysis of the focal mechanisms of these tremors using the seismic moment tensor inversion method allowed to determine the most probable causes of their occurrence. They were mainly related to the processes of fracture and slip in the thick layers of sandstone deposited in the direct or main roof of coal seam No. 504. Therefore, active rock burst prevention was aimed mainly at fracturing high-strength roof rocks.

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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

Wojtecki Łukasz, Krawiec Krzysztof, Ćwiękała Mateusz, Dzik Grażyna

Geology, Geophysics and Environment

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2024

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Vol. 50, no. 4

323--340

EN

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 ap-proximately 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. Addi-tionally, the study determined the spectral parameters of the tremor, which possessed an energy of 9.8 × 107 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.

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Charakterystyka aktywności sejsmicznej występującej podczas eksploatacji pokładu 507 w KWK„Ruda" Ruch Bielszowice w skomplikowanych warunkach geologiczno-górniczych

Wojtecki Łukasz, Pakosz Rafał

Bezpieczeństwo Pracy i Ochrona Środowiska w Górnictwie

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2024

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nr 12

18--28

EN

Induced seismicity usually accompanies the mining of hard coal seams, including those destressed by the extraction of adjacent seams. Mining of another coal seam beneath longwall goaf in previously mined adjacent seams is often characterized by a specific pattern of seismic activity. Seismicity induced during such mining is usually low due to the prior release of stress in the rock mass. The vertical distance and the time that has passed since the adjacent coal seam was mined are important. Incidental high-energy tremors may occur near the edges of previously mined coal seams surrounding the longwall panel in the mined seam. Their occurrence is associated with the redistribution of stress in the rock mass. The extraction of another coal seam may disturb the state of stress-strain equilibrium existing in the rock mass in the area of the edges of previously mined seams, thus leading to the occurrence of strong tremors. The article analyzes the seismic activity during longwall mining of seam No. 507 under complex geological and mining conditions in the Bielszowice part of the Ruda hard coal mine. Previously, multi-seam mining was carried out in this part of the deposit for many years. A comparison was made of the seismicity occurring during the mining of seam No. 507 and seams deposited above. Based on the seismic moment tensor inversion method, the mechanism of strong tremors that occurred during the mining of seam No. 507, in the area of the edges of previously mined seams Nos. 418, 501 and 502 and the top and bottom layers of the thick seam No. 504, was determined. The rock burst prevention used was analyzed against the background of the geological and mining conditions accompanying the mining of seam No. 507.

PL

Sejsmiczność indukowana towarzyszy zwykle eksploatacji pokładów węgla kamiennego, także odprężonych w wyniku eksploatacji pokładów sąsiednich. Eksploatacja kolejnego pokładu węgla pod zrobami ścian w uprzednio wybranych pokładach sąsiednich cechuje się specyficznym wzorcem aktywności sejsmicznej. W artykule przeanalizowano kształtowanie się aktywności sejsmicznej podczas eksploatacji ścianowej pokładu 507 w skomplikowanych warunkach geologiczno-górniczych w KWK „Ruda" Ruch Bielszowice. Dokonano porównania sejsmiczności występującej podczas eksploatacji pokładu 507 oraz wcześniejszej, w pokładach zalegających wyżej. W oparciu o metodę inwersji tensora momentu sejsmicznego wyznaczono mechanizmy ognisk silnych wstrząsów. Przeanalizowano zastosowane środki profilaktyki tąpaniowej w kontekście uwarunkowań geologiczno- górniczych towarzyszących eksploatacji pokładu 507.

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Zagrożenie tąpaniami i profilaktyka tąpaniowa podczas eksploatacji ścianowej pokładu 507 na dużej głębokości w KWK Ruda Ruch Bielszowice

Wojtecki Łukasz, Gołda Iwona

Przegląd Górniczy

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2019

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T. 75, nr 12

10--17

PL

Eksploatacja pokładów zagrożonych tąpaniami w KWK Ruda Ruch Bielszowice jest prowadzona na dużych głębokościach. Eksploatacji tej towarzyszy wysoki poziom naprężeń pierwotnych i związane z tym zagrożenie tąpaniami. Czynnikami negatywnie wpływającymi na koncentrację naprężeń w górotworze są również zaszłości eksploatacyjne wytworzone podczas wieloletniej i wielopokładowej eksploatacji, zaburzenia w zaleganiu pokładów (uskoki, wymycia) oraz obecność grubych warstw mocnych skał w stropie pokładów, odpowiedzialnych za występowanie wysokoenergetycznych wstrząsów. Eksploatacja pokładów węgla w takich warunkach powinna być zaprojektowana w sposób minimalizujący zagrożenie tąpaniami, a aktywna profilaktyka tąpaniowa powinna być ukierunkowana na czynnik wpływający w największy sposób na ryzyko wystąpienia tąpnięcia, nie powodując jednak przy tym wzrostu poziomu pozostałych zagrożeń naturalnych (np. metanowego, pożarowego). W artykule przedstawiono kształtowanie się zagrożenia tąpaniami oraz zastosowaną profilaktykę tąpaniową podczas eksploatacji pokładu 507 ścianą zawałową na głębokości około 814-884 m w KWK Ruda Ruch Bielszowice. Aktywna profilaktyka tąpaniowa była oparta na strzelaniach torpedujących skały stropowe pokładu 507, w zasięgu oddziaływania zaszłości eksploatacyjnych w pokładach 502, 504 i 506. Eksploatacja pokładu 507 została pomyślnie zakończona, co pozwoli na dalszą eksploatację grubego pokładu 510 w tym rejonie.

EN

Exploitation of coal seams in Ruda Hard Coal Mine Part Bielszowice is carried out at large depths. High level of natural stress and the associated rockburst hazard occur during this exploitation. Other factors affecting in a negative way the stress concentration in rock mass are mining remnants, created as a result of mining of many coal seams and lasting many years, coal seams dislocations (faults, washouts) and deposition of the thick layers of competent rocks in the roof of coal seams, responsible for high-energy tremors occurrence. Mining of coal seams under mentioned conditions should be designed to minimize the rockburst hazard, and an active rockburst prevention should be focused on the factor affecting the most the risk of rockburst occurrence, but without causing any increasing of other natural hazards level (e.g. methane hazard, spontaneous fire hazard). In this paper the development of level of rockburst hazard and applied rockburst prevention during longwall mining with caving of coal seam no. 507 at the depth about 814-884 in Ruda Hard Coal Mine Part Bielszowice are presented. The active rockburst prevention was based on a long-hole destress blasting in roof rocks of coal seam no. 507, at influence range of mining remnants in coal seams nos. 502, 504 and 506. Exploitation of coal seam no. 507 was successfully completed, what will enable further exploitation of thick coal seam no. 510 in this area.