Damage Evolution and Quantification of Granite in a High-Temperature Environment

In order to reveal the damage evolution of rock under high temperature environment, granite was heated to 600 ℃, 800 ℃, 1000 ℃ and its fracture morphology was analyzed. Using digital image processing technology, damage mechanics and "damage micro element" theory, combined with the characteristics of granite micro cracks at various temperatures, a rock damage evaluation method was established and a quantitative study of rock damage was carried out. The results show that: The fracture characteristics of granite are related to the initiation and propagation of cracks, and the number and distribution density of cracks increase with temperature; In each temperature range, the micro crack length of granite obeys logarithmic normal distribution, and the internal damage forms are mainly short cracks, supplemented by long cracks; At different temperatures, the micro cracks of granite developed from unidirectional extension to multi-directional penetration, and the maximum damage degree was positively correlated with temperature. This study reveals the damage evolution law of granite internal cracks, and the damage evaluation method has important reference value for the stability evaluation of high-temperature formation rock and the maintenance of underground engineering.