Infrared Radiation and Acoustic Emission of Damage Evolution and Failure Precursory for Water-Bearing Coal

The instability and failure of water-bearing coal mass can lead to serious coal–rock dynamic disasters, such as mine water inrush. It brings severe challenges to the safety produce during coal mining activities. Facing to this, the fine monitoring and accurate prediction are the direct and effective solution. To explore the influence of water content on the infrared radiation (IR) and acoustic emission (AE) signals during coal destruction, uniaxial compression experiments of dry and water-saturated coal samples were carried out. The time–frequency response of AE and the change of three quantitative IR indexes after the head–tail difference and the first order difference processing are investigated, to further analyze the precursory information of the IR and AE response characteristics. The results show that the influence of water on damage and failure modes play significant role to promote the thermal energy value generated by thermoelastic effect and frictional thermal effect, which also changing the AE time–frequency characteristics. Water role promotes the increase of the average infrared radiation temperature (AIRT) in elastic stage and plastic stage, and weakens the AE activities obviously. The first order difference infrared variance (VIRT b ), first order difference infrared skewness (SKIRT b ) and first order difference infrared kurtosis (KUIRT b ) show significant abrupt changes simultaneously with the damage variable during different water-bearing coal rupture damage. For the sensitivity of abnormal precursor, SKIRT b have good effect similar to VIRT b , while it is weaker for KUIRT b , and water can promote their sensitivity. The surface damage measured by IR is local characterization of the overall damage localized by AE. The combination of SKIRT b and b value for accurate early warning can play an excellent effect. The results can reveal the monitoring and forecast information for coal–rock dynamic disaster prevention under water involvement.