This paper presents the problems associated with the rapid change of the rock stress-strain state in terms of increasing the rate of coal mining. Parameters of the roof collapse are determined depending on the rate of a longwall advancing under conditions of poor rocks. Statistical data are processed to obtain a general trend concerning the mining rate impact on the roof collapse. The statistical strength theory is applied to explain the increase in mined-out space and the size of hanging roof behind a coal face. Numerical simulation is carried out to determine a critical size of mined-out space that provokes a roof collapse. The area of yielded rocks is outlined using the criterion developed taking into account the rate of longwall advancing. A general regularity is obtained to determine the roof collapse parameters. The developed technics gives a possibility to predict the moment of general roof collapse at the initial stage of longwalling to prevent the negative effect of the rapid stress redistribution provoking joints propagation and intensive gas release. The estimation of the rock stress-strain state considering the rate of mining operations can be useful for tasks related to a new technology implementation. The statistical strength theory and failure criterion applied together provides adequate planning of mining activities and the assessment of natural hazards.
Seismic and rock burst hazards still currently appear to be important in most hard coal mines in Poland. Recently, there has been a significant increase in seismic activity in the Silesian rock mass, in comparison to previous years. In the period 2001-2010, hard coal mines experienced 33 rock bursts. The causes of rock burst occurrences are here presented, based on an analysis of the rock bursts that occurred in Polish hard coal mines. The scale of the rock burst hazard has been characterized with respect to the mining and geological conditions of the existing exploitation. The most essential of the factors influencing the status of rock burst hazard is considered to be the depth of the interval, ranging from 550 m to 1150 m. The basic factors that cause rock burst to occur are as follows: seismogenic strata, edges and remnants, goafs, faults, pillars and excessive panelling. The consequences of rock bursts are damaged and/or destroyed roadways. On this basis, the areas (ranges) of safe zones were selected as being those safe from rock burst hazard in roadways, according to the assessment conducted to establish different degrees of the risk. KEYWORDS: rock burst hazard, parameters of rock bursts, consequences of rock burstsThe methods and technology for reducing rock burst hazards have made great strides, and the number of rock bursts in hard coal mines decreased drastically from 39 in 1972 to 2-5 in recent years. Between 2001 and 2010, the total number of recorded rock bursts was 33 (Fig. 2; Patyńska, 1989 Patyńska, -2010.
Abstract:The paper presents the characteristics of seismic tremors and rockbursts that occurred between 2001 and 2015. The characteristics are based on a general description of the geological structure of the Upper Silesian Coal Basin (USCB). The level of seismic activity in the analysed period changed a number of times and depended on the intensity of mining works and diverse mining and geological conditions in each of the five regions where tremors occurred (Bytom Trough, Main Saddle, Main Trough, Kazimierz Trough, and Jejkowice and Chwałowice Troughs) and which belong to various structural units of the Upper Silesia. It was found out that in the case of rockbursts the phenomena were recorded in three regions. These are: Main Saddle, Bytom Trough, and Jejkowice and Chwałowice Troughs. The so called Regional Rockburst Indicator (RWT) was estimated for each of the regions where the rockbursts had been recorded. The obtained values of RWT are presented against the Probability of RockBurst (PT) in a given area.
Based on a literature review concerning methane emissions in Poland, it was stated in 2009 that the National Greenhouse Inventory 2007 [13] was published. It was prepared firstly to meet Poland's obligations resulting from point 3.1 Decision no. 280/2004/WE of the European Parliament and of the Council of 11 February 2004, concerning a mechanism for monitoring community greenhouse gas emissions and for implementing the Kyoto Protocol and secondly, for the United Nations Framework Convention on Climate Change (UNFCCC) and Kyoto Protocol.The National Greenhouse Inventory states that there are no detailed data concerning methane emissions in collieries in the Polish mining industry. That is why the methane emission in the methane coal mines of Górnośląskie Zagłębie Węglowe -GZW (Upper Silesian Coal Basin -USCB) in Poland was meticulously studied and evaluated. The applied methodology for estimating methane emission from the GZW coal mining system was used for the four basic sources of its emission. Methane emission during the mining and post-mining process. Such an approach resulted from the IPCC guidelines of 2006 [10].Updating the proposed methods (IPCC2006) of estimating the methane emissions of hard coal mines (active and abandoned ones) in Poland, assumes that the methane emission factor (EF) is calculated based on methane coal mine output and actual values of absolute methane content. The result of verifying the method of estimating methane emission during the mining process for Polish coal mines is the equation of methane emission factor EF.
In the years 2001-2015, 42 rockbursts were recorded in Polish coal mines. For the past 15 years the scale of the phenomena has been similar and ranges from 1 to 5 rockbursts per year. However, the number of recorded high energy seismic tremors of 108 and 109J (E) energy that has occurred in recent years, 2 to 5, is alarming. According to the data, 27 of tremors of E > 108 J energy that occurred between 2001 and 2015 caused 3 rockbursts. Confronting these data with seismic activity from 1989-2000, it should be noted that only 2 events out of 99 rockbursts caused tremors with energies of E>108 J. Against the background of the scale of seismic and rockburst hazards, the geological and mining conditions of the Upper Silesian Coal Basin (USCB) have been analysed, detailing the structural units in which the rockbursts occurred. On this basis, the author characterised factors that impacts on the mining excavations resulting in rockbursts that caused damage on a larger scale. These rockbursts had the characteristics of mining catastrophes and weak earthquakes not recorded in mining statistics of natural hazards of USCB so far.
Streszczenie W latach 2001-2010 produkcja oraz liczba funkcjonujących kopalń węgla kamiennego w polskim górnictwie węgla kamiennego uległa znacznemu zmniejszeniu. Wydobycie węgla ze 102,78 · 106 Mg ograniczono do 76,15 · 106 Mg. Eksploatacja pokładów realizowana w 43 zakładach górniczych w roku 2001, na skutek likwidacji oraz połączenia kopalń, w roku 2010 dotyczyła 29 kopalń. Liczba 30 kopalń metanowych w roku 2001, w których wydobywano węgiel na poziomie 72,37 · 106 Mg, wroku2010 wynosiła21 kopalń, produkujących 52,18 · 106Mg węgla. Pomimo spadku produkcji węgla oraz malejącej liczby kopalń w Polsce wentylacyjna emisja metanu z procesów eksploatacji węgla kopalń metanowych od roku 2001 wzrosła o około 50 m3/Mg. W miarę upływu lat, wysiłki na rzecz odmetanowania niosą jednak pozytywny skutek. Pomimo wzrostu „strat" metanu w procesie odmetanowania, z roku na rok zwiększa się ilość metanu ujętego systemami odmetanowania. Z rozeznania i przeglądu literaturowego dotyczącego zagadnień związanych z emisją metanu w Polsce wynika, że w 2009 roku opublikowano Raport Krajowej Inwentaryzacji Emisji i Pochłaniania gazów cieplarnianych za rok 2007. Z Raportu Krajowej Inwentaryzacji... wynika, że brak jest danych szczegółowych dotyczących wskaźników emisji metanu z kopalń węgla kamiennego dla polskiego górnictwa. W związku z tym, przygotowano i obliczono szczegółowo emisje metanu z kopalń metanowych w Polsce. Zastosowana metodyka szacowania metanu wykonana została dla dwóch podstawowych źródeł jego emisji. Obliczono emisję metanu w trakcie procesu eksploatacji węgla jako emisję wentylacyjną oraz emisję z układów odgazowania. Takie podejście wynikało z wytycznych IPCC z roku 2006. Aktualizacja proponowanych metod IPCC (2006) szacowania emisji metanu z układów wentylacyjnych i z układów odmetanowania kopalń węgla kamiennego (czynnych i zlikwidowanych) w Polsce polega na założeniu, że wskaźnik emisji metanu (EF) obliczamy, opierając się na wydobyciu z koplań metanowych oraz rzeczywistych wielkościach metanowości bezwzględnej. Rezultat modyfikacji metody szacowania emisji metanu z procesów górniczych dla polskich metanowych koplań węgla kamiennego to równanie wskaźnika emisji metanu. W górnictwie polskim, od roku 2008 średni wskaźnik emisji z systemu węgla kamiennego utrzymuje się na stałym poziomie około 10 m3 C^/Mg. Uzyskane wyniki obliczeń emisji metanu w całym analizowanym okresie lat 2001-2010, mieszczą się w granicach 402-462 Gg (śr. 441,45 Gg).
Summary This paper presents the results of new research on ground-motion relations from three areas in the Upper Silesia Coal Basin (USCB) in Poland and compares them with of ground-motion relations. These three mining areas of the USCB were investigated in order to better predict ground motion caused by seismic events. The study focused on variations in regression parameters and predicted PGA (Peak Ground Acceleration) for different areas to better understand the influence of geology. To compare our results to previous models we had to unify the known Ground-Motion Prediction Equations (GMPE). Then, we used various regression models to predict the corresponding PGA values of a relatively strong USCB seismic event with an energy level of 108 J (ML = 3.3) and compared their results. The regression model parameters were compared to each other, particularly those related to energy and distance, which corresponds to a geometrical scattering (attenuation) of seismic waves as well as the influence of wave type (body or surface). Finally, building upon several established regression models, our analysis showed a strong linear correlation between two regression parameters corresponding to energy and distance. However, an open question remains whether this relation can be explained by physics, or, from a mathematical point of view, it is the effect of linear dependence of matrix vectors logE and logR. A comparison of different GMPEs allows for better verification of knowledge about the impact of tremors on ground motion in the USCB.
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