Characteristics of Mining Tremors within the Near-wave Field Zone

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Rock mass vibrations directly affecting the roof support in roadways and load on the support were continuously measured for 78 days in the deep seismic-prone coal mine Bobrek. The mine tremor of seismic energy E = 3E5 J (local magnitude, M L =2) and E = 8E3 J (local magnitude, M L = 1.1) located close to the tested roof support induced peak particle velocity weighted over 25 Hz, PPV w = 0.110 m/s and PPV w = 0.046 m/s. During the vibrations, an increase in vertical load of 82 kN and of 100 kN under the arch support was recorded. During vibrations induced by the other 395 seismic events, very low values of PPV W were recorded, i.e., less than 30 mm/s, and no significant increase in load was recorded under the arch support. However, the measurements showed that seismic events can cause a significant increase in load on the support, especially when the mine workings are located in the near seismic wave field, in which the parameters of peak particle velocity weighted over 25 Hz (PPV W) reach very high values. The influence of wave motion, which is caused by a seismic event, on the steel arch support was also analyzed with FLAC software numerical modeling and showed an important increase in the calculated load on the arch steel support.

Section: Introductionmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Peak particle velocity as an indicator of dynamic load exerted on the support of underground workings

Mutke¹

2016

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“…Due to safety reasons their localization in connection to the mining operations (Stec and Drzewiecki, 2000;Dubiński and Mutke, 1996), the intensity of their disturbance (Drzewiecki, 1996;2004) and the geometrical (Biliński, 1985) and mechanical parameters (Bukowska, 2005) which determine their ability to accumulate and release energy (Cabala et al, 2004) and seismic activity according to exploitation (Marcak and Mutke, 2013) are important. In this group of parameters, elasticity is of fundamental importance for proper prediction of the energy that layer accumulates as a result of deformation during mining exploitation, and their reduction by blasting methods (Koniček et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Determination of the value of the elastic modulus of the rock mass Esrm disturbed by a longwall operation

Drzewiecki¹

2015

This paper presents a method of determining the value of the elastic modulus of large-size piece of rock in the Bobrek mine. The basis of the analyses were relations between the mechanical and geometrical parameters of the rock mass in the environment coal seam 503, the intensity of its exploitation and its associated seismicity. The correct estimation of physico-mechanical and geometrical parameters of the rock mass is crucial for safety. As a result of changes in rock mass, due to the exploitation, some rock mass parameters change their value. The result of the analysis is a method of calculating the value of the elastic modulus Es for large fragments of rock disturbance by panel 1 operation. The results of the analyses are presented in graphical form. The results of the analysis indicate that for the correct seismicity forecasts, induced by coal seam operation, it is necessary to calculate the elastic modulus layers for the in situ conditions, i.e. for areas in which there are registered strong seismic phenomena. The developed formulas can be used both for ad-hoc analysis and long-term forecasts of seismic events energy. ARTICLE INFO

“…For example, sources of mining seismic events localized shallow under coal seam, require a different prevention than the mining tremors localized in direct rock roof. When the seismic events are located much deeper under mining coal seam and are far from excavations, the amplitude of ground motion are significantly damped and dynamic loads to mine workings are relatively low and don't cause danger to the stability of mine workings and miners (Dubiński and Mutke, 1996;Mutke, 2011;Dubiński and Mutke, 2012).The spatial location of seismic sources and analysis of their position in relation to mine workings is therefore essential for rockburst hazard assessment and thus for safety in operation. This is a very practical aspect of the study foci of deeper mining tremors.…”

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confidence: 99%

Registrations of seismic foci under mining coal seam - the experience of Polish mines

Mutke¹

2013

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In the article the results of registering seismic events located under mining coal seam are presented. Such mining tremors have occurred in several Polish mines. The geological and mining conditions affecting the induction of that type of seismic events are shown. The mechanisms of deep seismic events (more than 1000m) triggered by mining are discussed in relation to regional geology. The most deep mining seismic events in Upper Silesia were related to regional geological structures focusing stress (e.g. syncline) or tectonic structures (younger faults), where mining stresses were only additional factor to trigger strong regional seismic events. The tremors were characterized by a shear mechanism in the source (double-couple forces). Tremors located directly under the performed operation, usually characterized by an uniaxial tension mechanism, associated with the regional tension axis and the space created during the operation of the coal seam, causing pushing loaded rock-mass into new gobs. Proposed methods of seismic monitoring for case of seismic events location under mining coal seam are discussed.