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Stress state interpretation based on focal mechanism solution
Ptáček, Jiří ; Mořkovská, E.
Důlní otřesy vznikají za spolupůsobení přírodních a technologických faktorů. Obecně se má zato, že hlavními příčinami horského otřesu jsou nepříznivé geologické a geomechanické vlastnosti strukturních jednotek horského masivu a konsekventně tím způsobená nepříznivá, nerovnoměrně rozložená napěťová pole. Pro verifikaci tvaru napěťových polí a strukturního, napěťodeformačního modelu interpretovaného na základě paleonapěťové analýzy v české části hornoslezské pánve byla v rámci řešení projektu GAČR realizována měření pro zjišťování recentních napětí. Záměrem výzkumu bylo vytvoření modelu napěťodeformačních polí v sedimentárním uhelném ložisku a jeho srovnání s původním modelem interpertovaným na základě paleonapěťové analýzy. Pro studium byla vybrána nejvýchodnějčí část karvinské dílčí pánve.
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Stress - one of the most important mining influenced factors
Waclawik, P. ; Ptáček, Jiří
Stress is one of the basic factors affecting rock massif behaviour by decisive way. Knowledge of stress fields facilitates projection and successful realization of workings (e.g. stability check of workings, behaviour of proposed supports, spatiotemporal situation of workings). Within the scope of sedimentary deposit of Karvina subbasin were used data from structure-tectonic analysis and from measures in situ by overcoring and hydrofrac methods for determination of natural stress state and its orientation. This report deals with contemporary recognition of stress fields in the eastern part of Karvina subbasin. There are also disscussed problems of long working line depending on orientation and size of horizontal stress in this report. Last but not least there is described new knowledge about geological-tectonic structure of Karvina subbasin.
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Test equipment for measurement of the rock fracture toughness
Vavro, Leona
Presented contribution provides basic knowledge of development in the methodology of rock fracture toughness measurement in the laboratories of the Institute of Geonics AS CR in Ostrava. Fracture toughness is a relatively new parameter in geomechanics; the laboratory preparation of rock specimen is very time consuming. The fracture toughness of rocks may be practically used in a wide range of application; e.g. prediction of the anomalies in the geomechanics processes like the rock bumps.
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Topical issues connected with necessity of improvement of mining hazards prevention
Drzewiecki, J. ; Kabiesz, J. ; Przeczek, A. ; Koníček, Petr
Many mine induced seismic events are monitored in Upper Silesian Coal Basin both in Czech and Polish parts. In some cases these seismic events are attendet by rock bursts. Many broadly-based researches are carried out by Czech and Polish science institutions to explain the rockburst genesis. For all that we consider rockburst as hardly predictable mining risks. The contribution focuses on rockburst control solution. The examples of the stress-strain monitoring methods used by both Polish and Czech researchers are described together with some useful rock burst prevention methods. The high level of knowledge of the determinative parameters of the rockbursts occurrence help to create effective rockburst model. Anyway the research collaboration in the area of rock burst study improve the degree of mining safety.
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Evaluation of effectiveness of destress coal blasting fro stress release
Koníček, Petr ; Przeczek, A.
Destress blasting in the coal seam are important active rockbursts measures in conditions of Czech part of the Upper Silesian Coal Basin. Destress coal blasting involves regularly setting off carefully tailored blasts in the fractured coal immediately ahead of a mining face, so as to encourage slip on pre-existing fractures, in order not to allow the accumulation of high strain energy density in the rock mass. In some cases high stress in coal seams (or surrounded rocks) can be reduced. In cases that we demands high stress release we evaluates effect of stress release. Evaluation of stress release is carried out the same procedure without difference between destress blasting in rock and in the coal seam. Paper describes the first analysis of destress blasting in coal seams realised in period 2008 – 2010 (source of seismological databases, about 1200 data). The result of analysis shows of necessity of separate system of stress release evaluation by destress blasting in coal seams and rocks.
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