Experimental study on rockburst test of marble based on acoustic emission amplitude-frequency distribution

In order to carry out comparative analysis on the distribution of amplitude and main frequency of acoustic emission signals before and after rockburst, and to explore the essential characteristics of acoustic emission signals generated by marble in the rock burst stage and the inherent law of rock burst, this paper employed the three-way loading and one-way unloading methods to simulate the stress state change process of rock. Two marble rock burst simulation experiments were carried out on standard specimens. Three-dimensional stress time curve and acoustic emission signal were collected during the experiment. The rockburst experiment process was divided into three stages:initial loading stage,loading and unloading stage and rockburst stage by analyzing the three-way stress time-history curve, and the amplitude and frequency of the acoustic emission signal in different experimental stages were compared and analyzed.In terms of the distribution law, the concept of density distribution of acoustic emission signals in the amplitude-frequency plane was proposed. The distribution law of acoustic emission signals in the amplitude-main frequency plane before and after rock burst was analyzed.The internal destruction law of rockburst occurred in marble was studied when the density of the transmitted signal was the highest in the amplitude-main frequency plane. The results show that the intrinsic natural frequencies of acoustic emission of marble failure do not change with the change of loading stress in the two frequency bands centered at 90 kHz and 270 kHz, and the distribution law of amplitude-frequency in different stages has obvious difference.The highest frequency of acoustic emission events in the rockburst stage is not less than that in the loading stages, and the highest amplitude of acoustic emission occurs in the rockburst stage. The average main frequency of AE in rockburst stage is more than 200 kHz, and the maximum amplitude and average main frequency of AE in rockburst stage are larger than those in loading stage, which indicates that the rock in the rockburst stage has undergone more severe damage.