Rock burst process of limestone and its acoustic emission characteristics under true-triaxial unloading conditions

摘要

The rock failure process is associated with acoustic emission (AE). Hence, violent rock failure processes such as rock burst under different stress paths in laboratory can be studied using the AE monitoring technique. In this paper, single-face dynamic unloading tests under true-triaxial condition were carried out for Paleozonic marine sedimentation limestone samples produced by blocks cored from 1140 m depth in Jiahe coal mine of China. Frequency-spectra analysis was conducted for the full-wave AE data and figures showing the relationship of frequency-amplitude of AE signals in rock burst stages were obtained. The dynamical damage process and characteristics of limestone under the test condition are summarized. It is found from the fast Fourier transformation (FFT) analysis of the AE signals that there exist two main frequency ranges, i.e. lower (60-100I