Abstract: Uniaxial and triaxial compression tests have been carried out on pure salt rock to study the relationship between damage variable and fractal dimension of salt rock in the deformation and failure process. The damage variable and fractal dimension in the deformation and failure process of salt rock have been studied by using the damage model based on acoustic emission ringing count and fractal dimension calculation based on the spatial distribution of acoustic emission event. The results showed that the fractal dimension of salt rock gradually reduced and the damage variable slowly increased in the deformation and failure process of salt rock. Moreover, each stage of the declined fractal dimension were corresponding to each stage of the increased damage variable. Before the failure of salt rock, the fractal dimension of salt rock was not significantly reduced and was different under different stress states. With the increase of confining pressure, the fractal dimension of salt rock gradually reduced. Under stress states of uniaxial compression and triaxial compression, the fractal dimension of specimen below to 2.42, 2.31 and 2.20 respectively indicated that the internal damage of specimen gathered together to form a macroscopic fracture surface, leading to the specimen deformation and failure. The confining pressure had obvious inhibitory effect on acoustic emission activities. With the increase of confining pressure, there were less acoustic emission activities in the deformation and failure process of salt rock. When the stress state of rock changed from the uniaxial compression process to triaxial compression process, it was found that in the initial loading period, the percentage of stress gradually increased when the fractal dimension of salt rock decreased rapidly. However, in the late loading period, the percentage of stress gradually increased when the fractal dimension of salt rock reduced slightly. In addition, the damage variable was small and energy releasing was less at the early loading time of the deformation and failure process of salt rock. While the damage variable fast increased and energy quickly released before the failure of salt rock.

Key words: the deformation and failure of salt rock, acoustic emission, fractal dimension, damage variable, energy