Abstract In order to investigate the characteristics of ultrasonic wave velocity and acoustic emission activity of salt rock under triaxial loading,the multi-level cycle loading tests were conducted using a device composed with the acoustic wave and acoustic emission testing systems. The variations of ultrasonic wave velocity and AE number of salt rock were consistent with the loading stress. In the loading process,the ultrasonic wave velocity increased and AE activity was intense. However,there were opposite characteristics when the stress was unloading. The higher level the loading stress was,the more significant the feature was. The loading level of the confining pressure had great influence on the ultrasonic wave velocity and acoustic emission activity. The rate of change of the ultrasonic wave velocity was greater and the AE events were more under the lower confining pressure than when the confining pressure were in a higher loading level. This can be explained by the principles of confining pressure densification. In the paper,the unloading modulus,the fracture density and the ratio of Felicity were used respectively to express the damage evolution for salt rock. Results showed that the features of fracture density and the ratio of Felicity had a good consistency with the salt rock damage,which reflected the process of damage fracture well. Because of the plastic deformation,the unloading modulus was not suitable for describing the damage.
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