Analysis of fracture characteristics of saturated sandstone based on infrared radiation variance

The use of infrared radiation technology for monitoring rock stability and failure has been a common practice. However, the presence of groundwater significantly compromises the precision of infrared monitoring. This study employs scanning electron microscopy technology and PFC simulation to examine the micro-fracture development and infrared radiation variance (IRV) characteristics in dry and saturated sandstone conditions, and establishes a direct relationship between the two. The findings of this research indicate the following: (1) Saturated sandstone exhibits a substantially weakened internal structure, with the number of cracks at peak strength is approximately twice that of dry sandstone,the strength, peak stress, and elastic modulus of the saturated samples decreased to 56% and 59%, respectively. (2) The surface IRV characteristics of saturated samples are notably more pronounced, with an IRV value 9.57 times that of dry rocks. (3) Two infrared radiation variance indicators have been introduced to delineate different fracture stages of sandstone: "slow fracture variance" (SFIRV) denotes the initial crack formation in sandstone, while "rapid fracture variance" (RFIRV) characterizes a rapid fracture stage marked by a significant increase in crack development, serving as a precursor to complete sandstone fracture. (4) The relationship between IRV and the quantity of internal fractures adheres to a power function. A mathematical model for Fracture-IRV has been established, demonstrating a high degree of consistency with actual experimental results. The outcomes hold valuable implications for infrared monitoring research in deep engineering that may encounter groundwater-related challenges, such as tunnel and coal mining.