Infrared Radiation Characteristics During Crack Development in Water-Bearing Sandstone

We studied the infrared radiation (IR) characteristics of sandstone cracks with different water contents. We propose a new IR-based method to distinguish the initial development and damage point of cracks. The maximum variation of IR variance shows a quadratic relationship with water content. By defining crack initiation and damage using a stiffness stress curve, it can be concluded that the crack initiation and crack damage IR variance thresholds show a quadratic relationship with water content. The proportion of the two thresholds at the maximum IR variation amplitude does not change with increasing water content, yielding ratios of 47.51% and 78.19% for crack initiation and crack damage, respectively. The rock stress threshold of crack initiation and damage show a negative logarithmic relationship with their respective IR variance thresholds with correlation coefficients above 0.90.