Acoustic emission and thermal infrared precursors associated with bump-prone coal failure

Coal bump is sudden catastrophic failure of coal and usually causes serious problems to underground coal mining. The acoustic and thermal infrared radiation (TIR) characteristics of bump-prone coal under uniaxial compression and cyclic loading conditions are investigated in this study. The monitoring system consists of a TIR observation system, a stress and strain measurement system and an acoustic emission monitoring system. Precursory information for impending failure of coal samples is collected, including TIR, acoustic emission and strain precursors. Moreover, the response speed and the sensitivity of different monitoring systems during the cracking events in the samples are studied under different loading conditions. The microstructure of coal sample is analyzed by X-ray computerized tomography (CT) and scanning electron microscope (SEM). The experiment results show that 0.9 sigma(c) (sigma(c) is the compressive strength) and 0.82 sigma(c) can be regarded as the stress-caution-points for the failure of bump-prone coal under uniaxial compression and under uniaxial cyclic compression, respectively. They are much higher than 0.79 sigma(c) as the stress-caution-point for the normal coal samples. It is also indicated that the temperature at coal surface or in the coal mass should be monitored at the perimeter of the site with anticipated collapses. It can be a valuable tool to obtain the precursors for mine disaster control such as coal bumps, gas outburst and water inrush. (C) 2010 Elsevier B.V. All rights reserved.