## 3 Results Analysis  
### AE Amplitudes  
The AE amplitude evolution characteristics of intact specimens and jointed specimens from different types of tests were compared. Considering the difference in loading time between the various tests, the ratio of loading to peak load (\(\sigma/\sigma_{peak}\)) was used as the horizontal axis for the unified comparative analysis of the three tests, with a minimum scale value of 0.1 \(\sigma_{peak}\). In the tensile test, the peak stress of the intact specimen was 0.75 MPa, and the number of AE events to peak stress was 85,634. In the compressive-shear test, the peak stress of the intact specimen was 11.24 MPa, and the number of AE events to peak stress was 3645. In the tensile-shear test, the peak stress of the intact specimen was 2.76 MPa, and the number of AE events to peak stress was 94,865. In the tensile test, the peak stress of the jointed specimen was 0.34 MPa, and the number of AE events at peak stress was 16,253. In the compression-shear test, the peak stress of the jointed specimen was 6.53 MPa, and the number of AE events at peak stress was 16,103. In the tension-shear test, the peak stress of jointed specimen was 1.66 MPa, and the number of AE events at peak stress was 36,972. A comparison of the AE amplitude distribution versus loading stress level for the three types of tests is shown in Figure 3.  
From Figure 3a,b, it can be seen that the amplitude distribution in tensile tests is relatively scattered, ranging from 40 to 100 dB, and the pattern is the same for intact and jointed specimens. From 20% \(\sigma_{peak}\) to 60% \(\sigma_{peak}\), the AE amplitude is mainly between 40 and 55 dB, and there are sporadic AE signals with a high amplitude of 55-80 dB, indicating that the crack scale is small at the early stage of loading, and micro-cracking is predominant. From 60% \(\sigma_{peak}\) to 80% \(\sigma_{peak}\), the AE signals are abundant. However, the amplitude remains primarily between 40 and 55 dB, but the number of signals with high amplitudes larger than 55 dB increases significantly, and there are signals with high amplitudes larger than  
Figure 2: The test and monitoring equipment (The name of the equipment is “Tension-Compression-Shear” multifunctional rock mechanics testing machine). 90 dB in the intact specimen at this stage, indicating that large-scale cracks have begun to appear. The number of cracks is significantly increased. After 80% \(\sigma_{peak}\), the AE amplitude is more evenly distributed in the range of 40-75 dB, with sporadic, very-high-amplitude signals, indicating that the number of microcracks in the specimen has been significantly reduced, and large-scale fractures have formed. The distribution of AE signals of compressive-shear failure before the peak strength is primarily in the range of 40-55 dB, which is substantially less than tensile failure, showing that small-scale microcracks are prominent in the compressive-shear stress state (Figure 3c,d). Few AE signals between 55 and 70 dB exist at the early loading stage and near the peak strength. It is worth noting that the peak strength does not coincide with  
Figure 3: AE amplitude distribution characteristics in three test types. (**a**) Specim T1; (**b**) specimen T2; (**c**) specimen CS1; (**d**) specimen CS2; (**e**) specimen TS1; (**f**) specimen TS2. the maximum AE counts, and the macroscopic shear fracture surface has not yet been pierced. The difference in the distribution pattern of AE signals between intact and jointed specimens in the tensile-shear test is more significant than in the previous two types of shear tests, as shown in Figure 3e,f. The intact specimen's amplitude distribution is primarily in the 40-70 dB region, with similar amplitude distribution characteristics at different loading moments.