monitoring the fracture damage evolution process of flawed rocks and its temporal fractal characteristic

Investigating the progressive fracture process of rock masses containing flaws holds significant importance for assessing the stability of rock engineering projects. to study the fracture evolution behaviors of rocks with pre-existing flaws, uniaxial compression tests are carried out on red sandstone specimens containing two parallel flaws with different ligament angles (β). two monitoring techniques, including acoustic emission (ae) and high-speed camera, are utilized to capture the cracking process of flawed rocks. this investigation primarily examines the effect of β on the mechanical properties of flawed rocks. subsequently, the fracture progression in these rocks is characterized using the interevent time function f(τ), which represents the rate of ae events. it is evident that the initiation, coalescence, and failure modes of flawed rocks are notably influenced by β. furthermore, we employed fractal theory to explore the fractal characteristics of flawed rocks; thereby, enhancing our assessment of their fracture damage process. two parameters derived from fractal analysis, including correlation dimension d and its change rate η, can be served as the damage indicators to characterize the fracture process of flawed rocks. d varies from 1.5 to 5 in the absence of macrocracking. although it ranges from 0.5 to 0.7 during macrocracking occurrences. ultimately, d approaches near-zero levels upon reaching ultimate failure. notably, η displays a substantial increase beyond 0% when macrocracking occurs. the sharp decline in d and the rapid ascent in η can be considered crucial early warning indicators for the onset of macrocracking in flawed rocks. © the author(s), under exclusive licence to the iran university of science and technology 2023.