The rockbursts in the Upper Silesian Coal Basin in Poland

SELECTED METHODS OF ROCK STRUCTURE DISINTEGRATION TO CONTROL MINING HAZARDS WYBRANE METODY DEZINTEGRACJI STRUKTURY SKAŁ DLA ZWALCZANIA ZAGROŻEŃ GÓRNICZYCHNatural hazards are inseparable element of underground mining, particularly of coal mining process. They are combated on a regular basis by many measures and effectiveness of these measures determines work safety in mines. Attempts to improve the effectiveness, presented in the paper is based on interference of seismic waves generated by blasting in a selected area of the rock mass and on modification of blasting technology. Preliminary results of detonating classical and new type of explosives in specific temperature and pressure conditions are analyzed. Theoretical and practical consideration of obtaining an interference effect of seismic waves is discussed. A device for making systems of starting notches and a construction of a chamber to test explosives are presented.Keywords: mining hazards, rock structure disintegration, blasting technology Nieodłącznym elementem podziemnego górnictwa, szczególnie węglowego, są zagrożenia naturalne. Ich zwalczanie jest codzienną praktyką, a jego skuteczność decydująco wpływa na bezpieczeństwo pracy. Przedstawione w artykule próby poprawy tej skuteczności obejmują badania efektu nakładania się w wybranym obszarze górotworu drgań generowanych robotami strzałowymi oraz informacje o próbach modyfikacji strzelniczych technik szczelinowania skał, a także wstępne wyniki badania charakterystyk eksplozji klasycznych i nowych materiałów wybuchowych w nietypowych warunkach temperatur i ciśnienia.Omówiono między innymi teoretyczne i praktyczne warunki uzyskiwania efektu interferencji drgań oraz przedstawiono urządzenie do wykonywania systemów tzw. szczelin zarodnikowych i konstrukcję komory będącej elementem stanowiska do badania MW.

Section: Introductionmentioning

confidence: 99%

Selected Methods of Rock Structure Disintegration to Control Mining Hazards / Wybrane Metody Dezintegracji Struktury Skał Dla Zwalczania Zagrożeń Górniczych

Kabiesz¹,

Lurka²,

Drzewiecki³

2015

“…Whereas an increase in water inflow in mine workings results in changes in moisture of geological surrounding of specific values of strength-deformation parameters (Bukowska, 2005(Bukowska, , 2013. Hence the changes in properties of rocks under influence of drainage or saturating them with water (Bukowski & Bukowska, 2008, 2012, and as a result changes in hydrogeological conditions; including conditions and directions of water flow in workings and in the rock mass as well as ability to accumulate it (Haładus et al, 2005).…”

Section: B)mentioning

confidence: 99%

“…Evaluating water hazard in the areas of safety pillars it is impossible to avoid evaluating rockburst hazard, including the method employing the parameters determining rockburst susceptibility of the rock mass (Bukowska, 2012;Bukowska et al, 2012). Rockburst phenomena and high energy tremors of the rock mass disturb stability of the pillars and lower their strength.…”

Section: Research Tools To Evaluate Water Hazards In Today's Reality mentioning

confidence: 99%

Evaluation Of Water Hazard In Hard Coal Mines In Changing Conditions Of Functioning Of Mining Industry In Upper Silesian Coal Basin – USCB (Poland)

Bukowski¹

2015

Water hazard has been accompanying underground mining since the first mines were built. The hazard is particularly often in the areas of mines situated in hydrogeologically outcropped part of USCB and in water rich formations of Cracow Sandstone Series. To plan properly mining actions and technical measures at each stage of life of a mine it is necessary to evaluate hydrogeological and geomechanical conditions and their changes. The conditions determine formation, occurrence and volume of the most serious sources of water hazard. Symptoms obtained in geomechanical tests and observations of forming and dewatering reservoirs of underground water, show that it is necessary to update constantly evaluation and classification of sources of water hazard or the state of water hazard in the coal mines of USCB.Development of underground mining in , which resulted in a quick increase in production, determined development and the range of influence of mining operations on the rock mass and the influence on the state of drainage and saturation of the rock mass. The result of the changes was an apparent influence on the changes in the state and shaping water hazards in the course of time. Since 1989 economic conditions of functioning of mines have been tightly associated with the conditions and rules of market economy. As a result of each of the so-called restructuring of mining activity a certain number of mining companies was closed, merged or split. The consequence is that in the vicinity of active mines and prospective mining areas, more and more often there are partially or completely flooded abandoned coal mines. Flooded coal mines have changed and still do hydrogeological conditions of their surrounding and force active mining companies to introduce changes in mining activities they are planning and conducting. The current state of flooding mine workings, is a result of realizing previous plans of restructuring mining industry, and all the changes of the state require hydrogeological documentation and evaluation of water hazard.In the today's conditions of functioning of mining industry, sources of water hazards like water reservoirs in goafs, are one of six main types of sources of hazard, and at the same time the biggest problem and the most serious threat for active mine workings. As the hydrodynamic conditions in the closed areas stabilise and the water piles up close to the surface, an increase in the influence of reservoirs on the state of environmental and public hazard (subsidence, overflowing, flooding, pollution of water in the aquifers located in the overburden and surface water).As there is a qualitative change in the directions, causes and sources of water hazard, it shall be expected that the changes will tend to increase the threat level from the closed mines. Hence since

“…These parameters may be used directly to assess natural hazards, such as the dynamics of rocks and rockmass deformation, which is indispensable for describing such methan hazards (Krause & Łukowicz, 2012;Dziurzyński & Krause, 2012;Koptoń & Wierzchowski, 2014) and geomechanical hazards as sejsmic hazard (Butra et al, 2001;Mutke et al, 2009;Marcak & Mutke, 2013), and rockbursts (Kabiesz 2010), cave-ins, and gas and rock outbursts. They also play an important role in forecasting rockburst hazards in the mined areas by using them to evaluate the susceptibility of the rockmass to rockbursts (Bukowska 2006(Bukowska , 2012. The post-critical mechanical parameters of rocks are also used in forecasting other natural hazards associated with mining activities, e.g., water hazards (Bukowski, 2009(Bukowski, , 2015Bukowski & Augustyniak 2013), especially in collieries in the vicinity of water reservoirs formed in goafs of abandoned collieries (Bukowski, 2010).…”

Section: Introductionmentioning

confidence: 99%

Post-Critical Mechanical Properties Of Sedimentary Rocks In The Upper Silesian Coal Basin (Poland)

Bukowska¹

2015

In this paper, we present the results of a study of the Upper Carboniferous sedimentary rocks of the Upper Silesian Coal Basin (USCB) in Poland. We examined the hard coals, which belong to various stratigraphic units of Upper Carboniferous coal-bearing strata, and waste rocks, i.e., sandstones, mudstones, claystones. We present the results of tests of their post-critical mechanical properties. These results are from tests of the post-critical modulus, residual stress and residual deformation from experiments using a servo-controlled testing machine (MTS) with uniaxial compression and conventional triaxial compression. We applied confining pressures of up to 50 MPa at a strain rate of 10 -5 -10 -1 s -1 (0.003-6.0 mm/ sec). The confining pressure applied in the triaxial compression tests reflected the conditions of current and future mining activities in the USCB at depths exceeding 1.300 metres. The strain rate applied in the tests reflected the values observed in the rockmass surrounding the mine workings and the rate of certain geodynamic phenomena occurring in the Carboniferous rockmass in the USCB, e.g., rock bursts. We present the values of the sub-critical modulus of coals and waste rocks, the functional relationships between the post-critical modulus and uniaxial compression strength, which are described using an exponential function of high correlation coefficients of the given rocks, and an exponential relationship between the post-critical modulus and the longitudinal elasticity modulus (Young's modulus). Based on the results of tests of the post-critical properties of the Carboniferous rocks under triaxial compression and at various strain rates, we devised the functional relationships between the properties of the rocks and the confining pressure. The dependence of the post-critical modulus of the sandstones and claystones on the confining pressure is described using a polynomial function of degree 2, and that of the coals is described using an exponential function. The relationship between the residual stress and residual deformation in the rocks and the confining pressure was described using a linear function. The obtained results of tests have a practical application in forecasting behaviour of rocks located deep, and designing safe exploitation of mineral deposits. Confining pressures of up to 50 MPa used in the conventional triaxial compression tests allowed us to predict the behaviour of the rock mass at large depths. These data provide general knowledge of the tendencies in behaviour of rocks at substantial depths and the ability to design safe methods of mining deposits of various raw materials, including energy sources. These deposits are mined from increasingly great depths as the reserves are gradually exhausted and collieries of the largest European coal basins are continuously reconfigured.