Analysis of AE Time-Frequency Characteristics of Granite and Fine-Grained Granite

In order to further study the characteristics of crack evolution in different granites, uniaxial compression acoustic emission experiments were carried out on granites and fine-grained granites. It is found that by comparing the event rate, cumulative event number, energy rate and cumulative energy, the crack initiation ability of fine-grained granite is weaker than that of granite in the unstable crack growth stage, and the brittle character is stronger in the post-peak failure stage. The proportion of high-amplitude AE signals in granite is about twice that of fine-grained granite, and the proportion of high-amplitude AE signals in granite is more, and the damage is more intense. The AF value of fine-grained granite is higher than that of granite before the main fracture occurs, and the fine-grained granite has a higher proportion of tension cracks before the main fracture occurs. It is found that the inflection point of "fluctuation increasing- fluctuation decreasing" can be used as the critical failure precursor point of the sample. The evolution law of different types of AE signals in each stage of the sample is analyzed, and it is found that a large number of low amplitude and medium frequency AE signals appear in the granite in the stable crack expansion stage, indicating that more damage will be accumulated in the granite at this stage.