沿層掘進におけるAE活動の計測

Abstract

The acoustic emission activity from coal gas outburst was monitored during an entry drivage by blasting against the 11th coal seam in SUNAGAWA Coal Mine. In this observation, the source location analysis was conducted to determine the location of the acoustic emission activity which occurred prior to the coal and gas outburst using a multi-channel acoustic emission monitoring system. Moreover, themethane gas concentration in the driving face were measured successively after blasting.As the observational results, both acoustic emissions and gas emission after blasting increased and decreased remarkably in the approaching process of an entry driving face to outburst-prone fault zone, as well as the cases of cross-measure drivages presented in the first report of this study. Additionally, the continuous AE waveforms similar to the waveforms of gas outbursts were detected immediately after each blasting prior to the coal and gas outbursts. On the other hand, from the source location analysis and the frequency distribution of acoustic emission events against median frequency, it was revealed that the acoustic emission activity occurred locally ahead of the driving face. Therefore, these flactuations in acoustic emission activity and gas emission after blasting in the approaching process of driving face to outburst-prone area seem to be related to a local fracturing activity in the gas outburst source ahead of the driving face.