岩石循环加载和分级加载损伤破坏声发射实验研究

对循环加载和分级加载条件下岩石损伤破坏全过程的声发射规律和频谱特性进行了研究。结果表明，声发射与载荷变化或岩体变形破裂密切相关。循环加载过程中当载荷超过前期最大值时声发射信号增强，卸载阶段声发射信号随卸载过程逐渐减少，岩石的应力记忆特性具有明显的Felicity效应。分级加载时，当应力增加时声发射信号明显增多，应力稳定在低水平时基本不产生声发射信号；在高水平时，由于岩石内部损伤程度高，有零星声发射信号产生。岩石加载初期声发射主频较低，卸载阶段主频先增高后降低，恒载阶段主频最低，破裂阶段主频增高且主频带变宽，并出现次主频现象。

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. Changes of acoustic emission signals during complete failure process can preferably reflect the crack initiation and propagation in the rock. The study can provide theoretic basis for forecasting and monitoring dynamical disasters forecasting of coal or rock.