Differences in the acoustic emission characteristics of rock salt compared with granite and marble during the damage evolution process

Abstract

Rock salt cavities for energy storage are important elements of energy supply management and sustainability. The mechanical properties of other common rocks have already been adequately investigated, but a systematic characterization of the differences in acoustic emission (AE) characteristics among rock salt and other common rocks is needed. In this study, the AE characteristics of the full-regime uniaxial compression of rock salt and common rocks such as granite and marble were determined. A damage variable based on AE parameters and a methodology for its determination were established, including an analysis of the characteristics of the AE time–space evolution, the AE amplitude distribution and the damage evolution based on AE parameters. Clear differences were observed in the AE characteristics of rock salt compared with granite and marble during the damage evolution process. The AE activity and energy release of rock salt with coarse grains and nonuniform structures decreased gradually with increasing stress level. The AE activity of rock salt appeared in a continuous, group-occurring form. The AE spatial distribution of rock salt was relatively uniform, without a definite rupture surface. The AE amplitude distribution varied slowly, and the proportion of AE events with small amplitudes increased gradually during compression in rock salt. Moreover, the damage in rock salt predominantly occured during the pre-peak period, resulting in a large damage variable of 0.9 at peak stress. By contrast, the damage variables of granite and marble are only 0.5 and 0.1, respectively, at peak stress. Rock salt exhibited less damage when approaching failure, resulting in a gentler and steadier process. And the plastic characteristics of rock salt are relatively obvious. These properties, to some extent, ensure the safety of underground storage engineering when rock salt is chosen as the medium.