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Uncontrolled and excessive gas emissions pose a serious threat to safety in underground coal mining. In a recently completed research project, a suite of monitoring techniques were employed to assess the dynamic response of the coal seam being mined to longwall face advance at Coal Mine Velenje in Slovenia. Together with continuous monitoring of gas emissions, two seismic tomography measurement campaigns and a microseismic monitoring programme were implemented at one longwall top coal caving panel. Over 2,000 microseismic events were recorded during a period of four months. Over the same period, there also was a recorded episode of relatively high gas emission in the same longwall district. In this paper, a detailed analysis of the processed microseismic data collected during the same monitoring period is presented. Specifically, the analysis includes the spatial distribution of the microseismic events with respect to the longwall face advance, the magnitude of the energy released per week and its temporal evolution. Examination of the spatial distribution of the recorded microseismic events has shown that most of the microseismic activity occurred ahead of the advancing face. Furthermore, the analysis of the gas emission and microseismic monitoring data has suggested that there is a direct correlation between microseismicity and gas emission rate, and that gas emission rate tends to reach a peak when seismic energy increases dramatically. It is believed that localised stress concentration over a relatively strong xylite-rich zone and its eventual failure, which was also identified by the seismic tomography measurements, may have triggered the heightened microseismic activity and the excessive gas emission episode experienced at the longwall panel monitored.

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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.

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