Experimental study on infrared precursors of marble strain burst

To explore the precursors of strain burst for marble, the processes of stress-concentrated (SC) and dynamic-triggered (DT) strain bursts are simulated by the true triaxial rock burst experiments under different loading modes, and the infrared radiation temperatures of strain bursts are monitored by the infrared thermal imaging instrument. Additionally, the precursors of marble strain burst are analyzed according to the average infrared temperature difference (AITD), variance (AITV), heating rate, average infrared images and Fourier spectra. Furthermore, the differences of precursor characteristics among different strain bursts are discussed. The results show that the AITD, AITV and temperature rise rate increase significantly before strain burst. Moreover, the sudden increase of AITD is ahead of strain burst (10 ms and 20 ms, respectively for SC and DT), which can be used as an effective precursor of strain burst. Additionally, the AITV before DT strain burst will fluctuate slightly, and the heating rate has an obvious downward trend, which corresponds to the cooling process of the AITD. However, for the SC strain burst, the AITV and heating rate both have no obvious fluctuation characteristics. Moreover, the infrared temperature difference images before strain burst show the phenomenon of high- and low-temperature alienations, specifically, the average infrared image before strain burst of SC shows an obvious inverted "Y" high-temperature region, and that for the DT strain burst shows a downward movement of high-temperature region. Finally, the vertical Fourier spectra both show a large number of main components with high frequency and low amplitude for the two types of strain bursts.