## 5 Conclusions  
Based on RFPA\({}^{\text{3D}}\) numerical modeling and microseismic monitoring, the stability of the excavated geologically weak section of the #2 diversion tunnel in the Xulong Hydropower Station was analyzed and evaluated, with the following conclusions reached:  
1. Surrounding rock damage after excavation of the geologically weak section of the #2 diversion tunnel was modeled by using RFPA\({}^{\text{3D}}\). The maximum principal stress concentrated around the tunnel profile and at the corners of the side wall in the study area, and cracks were initiated and grew from the tunnel vault and bottom corner of the side wall until they penetrated the entire profile. Acoustic emissions also started to accumulate at the vault and corners of the side wall and then propagated along the floor and side wall. The acoustic emissions at the vault and corners of the side wall gradually increased in energy, making it a key monitoring target in the study area.
2. Microseismic events were mainly concentrated near the vault and footwall during the excavation of stakes K0+765 to K0+775. It was dominated by tensile failure accompanied by shear failure. The frequency of microseismic events could better reflect the frequency of excavation activities in underground plants, and microseismic monitoring helped infer the damage evolution of the rock during the instability failure process of the surrounding rock and delineate the potential risk area.
3. The RFPA\({}^{\text{3D}}\) numerical modeling results and the data collected by the actual microseismic monitoring system were consistent, which verified the damage area of the surrounding rock in the excavated geologically weak section. The vault and corners of the side wall, in particular, sustained the most serious damage, so it is necessary to pay close attention to this area and provide timely support. Microseismic monitoring played a key role in controlling the stability of the tunnel surrounding rock, and it is required to continue to strengthen microseismic monitoring and take effective measures to ensure the safety and stability of the slope during the construction and operation periods in the subsequent construction process.  
Figure 13: Comparison between numerical modeling and field monitoring.  
**Author Contributions:** [PERSON] investigated the geological and construction information of the engineering and wrote the first draft of the manuscript. [PERSON] conducted the literature review and carried out the numerical simulation. [PERSON] developed the overarching research goals and analyzed microseismic data. All authors have read and agreed to the published version of the manuscript.  
**Funding:** The research is supported by the National Natural Science Foundation of China (No. 42177143, 42277461), the Science Foundation for Distinguished Young Scholars of Sichuan Province (Grant No. 2020 JJQ0011) and the opening project (No. SKLGP2021K007) of the State Key Laboratory of Geohazard Prevention and Geoenvironment Protection.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The microseismic data related to this research is confidential and cannot be made public.  
**Acknowledgments:** Thanks are given to colleagues at the hydropower station for their valuable contributions to the project. Finally, the authors would like to thank the editors and reviewers for their valuable comments and constructive suggestions.  
**Conflicts of Interest:** The authors declare no conflict of interest.