Analysis of precursor and failure mechanisms of granite under high temperature: Based on acoustic emission and 3D-DIC perspectives

Abstract

In deep mining, underground oil and gas extraction, and other high-temperature rock engineering applications, the complex rock environment leads to damage and deformation of the rock. Studying the precursors of rock fracture and failure mechanisms at high temperatures is important for maintaining the stability of high-temperature engineering. This paper focuses on granite as the research object. It utilizes Acoustic Emission (AE) and Three-Dimensional Digital Image Correlation (3D-DIC) techniques to monitor the entire fracture process of granite under uniaxial compression at 25°C, 100°C, 300°C, 500°C, and 700°C. A mechanism for identifying the precursors of high-temperature granite fracture, considering both internal and external factors, is established. The failure mechanism of granite under uniaxial compression at high temperatures is revealed. The results indicate that as the heating temperature increases, the bearing capacity of the rock decreases. High-temperature granite transitions from predominantly tensile cracking to shear cracking. The sudden increase in the cumulative count of acoustic emissions (AE), the rise in damage stress, and the abrupt decrease in the b-value effectively reflect the crack development process within the rock. RA-AF can elucidate the evolution of crack types in high-temperature granite. By integrating full-field principal strain analysis with b-value analysis, the significant drop in b-value can accurately indicate the precursors to rock failure. Ultimately, an 'internal-external' synergistic mechanism for identifying failure precursors is established. As the temperature rises, the failure precursor point of the rock advances.The increasing temperature correlates with a gradual decrease in the quartz content of the rock, which impedes the transmission of force chains among granite particles. Concurrently, the bonding strength between mineral grains diminishes, fundamentally accounting for the variations in uniaxial bearing capacities and failure mechanisms of granite. The research findings have theoretical significance for understanding the identification of fracture information and failure mechanisms of rocks at high temperatures. They provide theoretical support for the occurrence mechanisms, early warning, and prevention of high-temperature rock engineering disasters.