The Monitoring of Acoustic Emission Accompanied with Advance Boring

Study on acoustic emission activity due to advance boring in coal seam

Abstract

In this research, the fracturing activity in coal seam due to advance boring was observed by applying the acoustic emission techniques in order to ascertain its preventive effect for coal and gas outburst
In the working faces of drifting, a transducer was installed near the drilling region. The detected signals associated with coal fractures were separated from drilling noises successfully, and were presented for the analyses on the waveforms, the frequency spectra and the parameters of fracturing activities. Consequently, itwas found that these analytical results offered the useful informations to estimate the hazard of coal and gas outburst in the coal seam ahead of driving faces. The main concluding remarks are as follows;
1) The acoustic emissions due to coal fractures during drilling occurred near the cutting points of the bottom of boreholes.
2) The acoustic emission activity accompanied with advance borings was extremely at a low degree in the relaxed region; and at a high degree in the region under a local stress concentration.
3) The location and the range of a local stress concentration were more clearly recognized from the histogram of acoustic emission counts per unit drilled length than that of volume of discharged cuttings.