Space-time evolution rules study on acoustic emission location in rock under cyclic loading

Abstract

An acoustic emission (AE) location experiment was performed on sandstone using an advanced AE test system. The space-time evolution rule regarding damage was analyzed under cyclic loading as well as AE. The results show that AE on static loading process is consistent with the damage evolution rule of compression and the elastic-plastic deformation phase; at the beginning of cyclic loading with low duration time and energy, AE events came from a small crack. The location result showed that most events occurred in the core zone forming at the static loading process, and the location points changed slowly. AE energy changed little during the metaphase of cyclic process. There was a modest increase of location points in every cycle. The tendency of steady development could be predicted from the AE location events. At the end of each cyclic loading, the quantity of AE events and energy increased quite rapidly, reaching a maximum at the last cycle. AE events had high energy and duration time. Location events changed quite rapidly and assembled and linked continuously in the core zone. At the same time, they expanded to the top of specimen. A macroscopic crack finally formed. In the postfailure process, some AE events still existed due to fracturing of gliding friction. Owing to the inner stress balance of rock even after loading stopped, minor AE events still occurred.