Abstract: Uniaxial compression tests were carried out on sandstone specimens with different fracture angles by means of digital image correlation method and infrared thermal imaging technology, the differentiation degree and rate of strain field and infrared radiation temperature field were quantitatively described by using the standard deviation and approximate derivative. The evolution law, variation mechanism and precursory anomaly characteristics of these two fields during the deformation and rupture processes of the fractured sandstones were analyzed, and their correlations were also discussed. The results show that the evolution process of standard deviation for strain fields can be divided into four stages: initial differentiation, initial acceleration differentiation, intermediate acceleration differentiation and accelerated acceleration differentiation. The evolution process of standard deviation for infrared radiation temperature field can be divided into three stages: initial differentiation, stable differentiation and accelerated differentiation. The standard deviations of strain fields and infrared radiation temperature fields have similar variation trend during the deformation and fracturing process of flawed sandstone specimens. The Pearson correlation coefficients between these two fields are in the range of 0.50 to 0.91, presenting a significant or high positive correlation. There are two peaks in the variation curve of differentiation rate for strain field before failure, corresponding to the initiation points of tensile crack and shear crack, respectively, which could be regarded as two precursor points. The differentiation rate of infrared radiation temperature field increases continuously before the initiation of shear cracks, which could also be regarded as a precursor point. Research results can provide a new method and theoretical basis for monitoring and forecasting the stability of fractured rock masses.

Key words: flawed sandstone, digital image correlation method, strain field, infrared radiation temperature field, precursor