Spatial-temporal infrared radiation precursors of coal failure under uniaxial compressive loading

In order to find out the abnormity of infrared radiation temperature field during the coal bearing failure process and express the infrared radiation characteristics quantitatively at the time of coal failure. In this paper, two quantitative analysis indicators based on variance, Variance of Original Infrared Image Temperature (VOIIT) and Variance of Successive Minus Infrared Image Temperature (VSMIT), were adopted to study the infrared radiation (IR) characteristics of coals during uniaxial compression loading. Original infrared images and successive differencing of infrared images were used to reveal the spatial distribution characteristics and evolution process of fractures, and the spatial-temporal precursors of coal failures were obtained. The precursor of upcoming failure (PUF) and the precursor of initial failure (PIF) were discovered. About 80% of the coal samples tested showed significant PUF at a stress level of about 93% (ranging between 86.3 and 98.0%) relative to the peak stress (σp) on average. Typically, the PUF was observed about 30.0 s prior to a failure. Furthermore, about a minute prior to failure, 30% of the coal samples showed significant PIF at a stress level of about 80% relative to σp on average. This study demonstrates the potential ability to use infrared remote sensing technology for forecasts and early warnings of natural and engineering disasters caused by rock failures, such as rock bursts, landslides and earthquakes.