Infrared precursor of pre-cracked coal failure based on critical slowing down

In order to study the precursor information of infrared radiation temperature of coal containing macro-cracks during load bearing damage, infrared monitoring tests of coal instability damage under different crack inclination angles are designed. Based on the critical slowing down theory, the variance and autocorrelation coefficients of the infrared radiation temperature series are calculated to reflect the damage precursors and provide a theoretical basis for early warning of coal and rock dynamic hazards. The results show that the infrared radiation sequences of pre-cracked coals have a critical slowing down effect. The autocorrelation coefficient and the variance of MIRT curve can be more accurate to find the precursor time of instability. In the critical slowing down analysis, the variance is more stable, and the lag step has a great influence on the autocorrelation coefficient. The infrared precursory information of the coal is mostly about 80% to 85% of the peak stress or instability time, and the horizontal fracture will make the failure precursory appear in advance.