Deformation and acoustic emission characteristics of hard rock under different unloading rates.

In this paper, triaxial loading and unloading tests under different conditions were carried out to explore the deformation and failure characteristics of hard rock marble, and the acoustic emission information of the test process was monitored synchronously to obtain the acoustic emission distribution characteristics. The test results show that: (1) when the confining pressure unloading rate is low, the rock yielding is more obvious, the damage peak is higher, and the Poisson effect is more obvious under loading and unloading, while when the unloading rate is high, it shows multi-stage damage; (2) there is a linear relationship between strain deviatoric stress flexibility and unloading rate, as the unloading rate accelerates, the circumferential and volumetric flexibility increases and the axial flexibility decreases; (3) the lower the unloading rate, the higher the confining pressure, and the main shear surface of the rock gathers a large number of tensile microcracks to form a shear zone, while the higher the unloading rate, the lower the confining pressure, and the main shear surface is thoroughly penetrated and ruptured; (4) acoustic emission can characterize the damage degree of marble in the process of loading and unloading, when the confining pressure is low, acoustic emission at the peak damage point appears sharp phenomenon, the overall damage increases with the accelerated rate of unloading, when the confining pressure is high, acoustic emission grows progressively, the overall damage decreases with the accelerated rate of unloading, the overall damage of the rock will appear " pre-peak to post-peak " hysteresis effect. [ABSTRACT FROM AUTHOR]