Experiment on acoustic emission of rock damage and fracture under cyclic loading and multi-stage loading

The acoustic emission regularity and spectrum characteristics of rock under cyclic loading and multi-stage loading during complete failure process were studied.The results show that the characteristic of acoustic emission is closely related to the load variation or the deformation fracture of rock.During cyclic loading process,acoustic emission signals are enhanced when the load is larger than the previous maximum value,acoustic emission signals are reduced gradually along with the unloading process,and memory characteristic of rock stress shows obvious Felicity effect.During multi-stage loading process,acoustic emission signals increase obviously when the stress increases,and few acoustic emission signals are detected in the low stress stage.Meanwhile,sporadic acoustic emission signals are detected in the high stress stage for the high extent of internal damage.The main frequency of acoustic emission is low in the initial loading stage.It increases firstly and then decreases in the unloading phase.The main frequency is the lowest during load stability period.It increases and broadens,with the sub-frequency in the fracture stage.