Effects of thermally-induced cracks on acoustic emission characteristics of granite under tensile conditions

Abstract

Temperature can affect the physical and mechanical properties of rocks. With the aim of better understanding the effect of thermally-induced cracks on rock failure process, we heated granite disks (up to 800 °C) to induce different degrees of thermal damage, which were then used for Brazilian tests . The acoustic emission (AE) technique was applied to collect AE signals throughout each test. Specifically, the effect of thermally-induced cracks on AE characteristics (AE spatio-temporal characteristics, damage parameters D AE , amplitude-frequency characteristics, and b -value) was studied. Our results show that the thermally-induced cracks increase with the treated temperature, leading to more AE damage occurring at the early stage of the loading process. The existence of a large amount of thermally-induced cracks causes the scattered AE distribution on the disks treated at 600 °C and 800 °C. The average dominant frequency of AE signals decreases with the treated temperature. The decreasing of high-frequency signals and the increasing of low-frequency signals can be explained by the different mechanisms of thermally-induced cracks and stress-induced cracks. The b -value increases with treated temperature and decreases with the increasing applied stress.