大理岩应变型岩爆红外前兆特征试验研究

Experimental study on infrared precursors of marble strain burst

为探究大理岩应变型岩爆的红外前兆特征,通过不同加载方式下单面临空的真三轴岩爆试验,模拟应力集中型和动力触发型岩爆的发生过程,使用红外热像仪监测两类岩爆的红外温度场变化过程,从平均红外温差、方差、升温速率、红外图像及傅里叶频谱图等方面分析了岩爆前兆信息,并探讨了不同类型岩爆前兆特征的差异。结果表明:岩爆发生前平均红外温差、方差及升温速率曲线均出现明显突增,其中平均红外温差突增分别提前应力集中型和动力触发型岩爆10,20 ms,可作为有效岩爆前兆;动力触发型岩爆发生前方差会出现小幅波动且升温速率有明显下降趋势,与温差曲线中岩爆前的一小段降温过程相对应,而应力集中型岩爆方差与升温速率无明显波动特征;岩爆前平均红外温差图像出现高低温异化现象,表现为:应力集中型岩爆前红外图像出现明显的倒“Y”型高温区域,动力触发型岩爆平均红外图像出现高温区域下移现象;此外,两类岩爆傅里叶频谱图中的垂直谱图均出现大量高频低幅的主要分量。

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.