Abstract. The current level of rockburst hazard in copper mines of the (LGOM) Legnica-Głogów Copper Belt Area is mostly the consequence of mining-induced seismicity, whilst the majority of rockbursting events registered to date were caused by high-energy tremors. The analysis of seismic readings in recent years reveals that the highest seismic activity among the copper mines in the LGOM is registered in the mine Rudna. This study investigates the seismic activity in the rock strata in the Rudna mine fields over the years 2006-2015. Of particular interest are the key seismicity parameters: the number of registered seismic events, the total energy emissions, the energy index. It appears that varied seismic activity in the area may be the function of several variables: effective mining thickness, the thickness of burst-prone strata and tectonic intensity. The results support and corroborate the view that principal factors influencing the actual seismic hazard level are regional geological conditions in the copper mines within the Legnica-Głogów Copper Belt Area.
This article concerns numerical modeling of the impact of mining operations on fault behavior, carried out on the basis of a calculation program based on the finite element method. The calculations and their graphic results related to the reactions of vertical discontinuity on the mining operations that run along its boundary under changing operating parameters, such as geometry of the field and direction of mining with respect to the fault, as well as the method of liquidation of the caving zone. The behavior of the fault was analyzed based on distributions in the plane of shear stress and slip, together with their range and energy dissipated due to friction. The results of numerical calculations made it possible to draw conclusions on the impact of faults and the impact of operating conditions of mining in their vicinity on the level of seismic hazard.Keywords: geomechanics, underground mining, faults, mining tremors W artykule w oparciu o program obliczeniowy bazujący na metodzie elementów skończonych przeprowadzono numeryczne modelowanie wpływu eksploatacji na zachowanie się uskoku. Obliczenia i ich graficznie rezultaty dotyczyły reakcji pionowej nieciągłości na prowadzoną wzdłuż jej granicy eksploatację górniczą przy zmieniających się parametrach eksploatacji, takich jak: geometria pola i kierunek wybierania względem uskoku oraz sposób likwidacji zrobów. Zachowanie się uskoku analizowano w oparciu o rozkłady w płaszczyźnie uskoku naprężeń stycznych i poślizgu wraz z ich zasięgiem oraz energię zdyssypowaną wskutek tarcia. Rezultaty obliczeń numerycznych pozwoliły na sformułowanie wniosków dotyczących oddziaływania uskoków oraz wpływu górniczych warunków eksploatacji w ich sąsiedztwie na wielkość zagrożenia sejsmicznego.
Rock bursts are a common hazard in Polish hard-coal mines. Their magnitude depends on the state of stress in the mining area, and on underground mining-induced seismicity. Both long-term and ongoing as-sessments of the capacity of the rock mass to generate tremors are based on geological and mining surveys, rock property measurements (in laborato-ries and in-situ) and observations involving signs of rock mass pressure, supported by available concepts applicable to geomechanical and geophys-ical measurements. These include seismic measurements, including profil-ing, scanning, passive/active geotomography and analytical techniques. This paper presents a comparative analysis involving exemplary results provided by both seismic and analytical methods for a selected panel in one of Upper Silesian Coal Basin (USCB) mines. For the purposes of our seismic measurements, we employed seismic tomography for the ge-otomographic reconstruction of velocity fields. Subsequently, we com-pared the results with the results of analytical modelling of rock stresses that relied on classical engineering solutions applicable to problems of me-chanics of deformable bodies. The tremor hazard analysis was based on observations of changes in P-wave velocity distributions in the coal seam environment relative to the evolution of the vertical stress concentration factor at the level of a potentially seismogenic roof layer.
Mining-induced seismicity in the area of development works and proper mining operations is one of the major determinants of the rockburst hazard level in underground mines. Rockburst hazard assessment in Polish collieries is performed by a variety of mining and geophysical methods, including seismic and seismoacoustic techniques, borehole surveys, small diameter drilling, rock strata profiling and analyses of geomechanical properties of rocks, geological structure and geological mining conditions. In the case of zones particularly exposed to potential hazards, it is recommended that analytical or numerical forecasts of the state of stress in the vicinity of workings should be used already at the stage of planning of mining operations. This study summarises the comparative analysis of seismic test data and analytical forecasts of the state of stress in five selected headings in one of the burst-prone collieries within the Upper Silesia Coal Basin in Poland (USCB). As regards the seismic data, duly defined quantitative indicators and energy criteria of the registered seismic activity are recalled in the assessment of rockburst hazard level during the roadheading operations. Analytical simulations utilise a developed geomechanical model and stress–strain relationships stemming from the principles of elastic media mechanics. From the standpoint of mining engineering practice, interpretation of results obtained by the two methods reveals how effective analytical models will be in prognosticating or verification of rockburst hazard conditions.
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