## 3 Results Analysis
### AE Peak Frequency  
For the three types of tests, the AE waveforms of the different tests were extracted, the FFT spectra of all the AE signals of the various tests were transformed, and the peak frequency distributions were counted. The maximum values of the peak frequencies of the AE signals of the three tests did not exceed 500 kHz, and the distribution of the peak frequencies of the different tests showed a three-band distribution. Based on the clustering characteristics of the peak frequency values, the AE signals below 50 kHz were classified as a band of low frequencies, 50-200 kHz as a band of medium frequencies, and above 200 kHz as a high-frequency band. The distribution of the peak frequency bands and the percentages of the three types of tests as the stress is continuously loaded are shown in Figure 4. In the tensile test, only low-frequency signals are generated until 60% \(\sigma_{peak}\) of the intact rock specimen. Only sporadic medium- and high-frequency signals are generated in the jointed specimen at this stage. In contrast, near the failure, the medium- and high-frequency signals of the intact and jointed specimens start to increase. In particular, only medium-frequency signals are generated during the 90-100% \(\sigma_{peak}\) loading interval for the intact specimen. In the compressive-shear test, the high-frequency signals are mainly generated in the initial loading stage, and the intact rock specimen has relatively more medium-frequency signals, accounting for 60.1%. In contrast, the jointed specimen still has mainly low-frequency signals, and both specimens have significantly more medium- and low-frequency signals near the failure. In the tensile-shear test, both specimens generate three frequency bands of signals throughout the loading process. The proportion of high-frequency signals is much greater than in the tension and compression-shear tests. However, all three tests are similar in that the number of medium-frequency signals increases significantly near the moment of failure, which can be an essential precursor to identifying failure. The peak frequencies of the jointed specimens under the three types of failure are selected for moving average processing (step size of 50) to investigate the evolution of the peak frequency distribution of the three types of testing. The peak frequencies of the three types of tests fluctuate and decrease with stress loading. The tensile and tensile-shear tests have similar patterns, with peak frequencies decreasing in the early loading stage and fluctuating in the medium and late stages. The compressive-shear test differs significantly from the other two tests because the peak frequency fluctuates considerably at the beginning of loading. In contrast, the peak frequency values are lower near the failure time and only fluctuate within a small range. There is currently no consensus on the relationship between tensile and shear cracking and the peak frequency. As the failure mechanism of compressive-shear tests has been studied more in previous research,the relationship between the peak frequency and cracks in compressive-shear tests was analyzed first. [PERSON] (2018) concluded that the early and medium stages of compressive-shear failure in jointed specimens are dominated by small-scale tensile cracks, with tensile cracks converging near the failure time and failing the bridge in the form of shear rupture. Combined with the peak frequency evolution features of the jointed specimen in Figure 5b, it was deduced that AE signals with high peak frequency belong to tensile cracks and those with low peak frequency correspond to shear cracks, but this is simply a qualitative conclusion. It is impossible to determine the quantitative division criteria between high and low frequencies, but it is clear from Figure 5 that the peak frequencies are above 50 kHz at the beginning of all three types of test loading.