# Mechanisms of Tunnel Rockburst Development Under Complex Geostress Conditions in Plateau Regions
## 6 Conclusions  
In this study, FLAC3D numerical models were constructed to investigate plateau tunnel engineering under complex tectonic influences, with geostress orientation, lateral pressure coefficient, and burial depth selected as the main variables to systematically explore the influence mechanisms of rockbursts under complex geostress environments. The main conclusions are as follows:  
1. Geostress orientation determines the location of rockburst occurrences. Numerical simulations indicate that local surrounding rock areas in the direction of the minimum principal stress (S\({}_{2}\)) on the tunnel cross section are prone to tangential stress concentration and elastic strain energy accumulation, becoming high-risk zones for rockbursts (Figures 7 and 8). Therefore, accurate measurement of geostress orientation is crucial for predicting rockburst locations. 2. Lateral pressure coefficient affects rockburst intensity and bursting pit extent. Analysis results show that under the same minimum principal stress in the cross section, an increase in lateral pressure coefficient significantly enhances tangential stress and elastic strain energy in local stress concentration zones, leading to markedly greater rockburst intensity and bursting pit extent (Figures 10 and 11). Particularly under high tectonic stress conditions, severe rockbursts may occur even in shallow tunnels. 3. Burial depth determines the overall risk level of rockbursts. As burial depth increases, geostress values generally rise, and tangential stress and elastic strain energy show increasing trends in multiple areas of the tunnel cross section (Figures 13 and 14). This not only intensifies rockburst severity but also expands the affected risk range, validating the understanding that \"the deeper the burial, the higher the likelihood of rockburst occurrence.\"* The three stress-related parameters exhibit distinct mechanisms of influence and should be individually identified and jointly evaluated. The orientation of in-situ stress primarily determines the spatial distribution pattern of rockbursts within the tunnel cross-section and serves as the dominant factor affecting their location. In contrast, the lateral pressure coefficient and burial depth mainly affect the magnitude of in-situ stress and thus respectively govern the intensity and overall trend of rockburst development (Figure 15). These findings suggest that adopting a controlled variable approach to isolate the effects of individual parameters can facilitate targeted rockburst risk prediction and mitigation strategies based on actual stress conditions encountered in engineering practice. This study primarily focused on the complex geostress field under strong tectonic influences and investigated the impact patterns of geostress orientation, lateral pressure coefficient, and tunnel burial depth as the main independent variables affecting rockbursts in plateau regions. The effects of tectonic geological bodies and geothermal activity, formed under complex tectonic processes, on rockbursts will be considered in future research. The study was conducted under clearly defined assumptions, namely, homogeneity and isotropy of the rock mass. Future research should aim to reduce such simplifications by considering the presence of fractures, faults, discontinuities, anisotropy, and heterogeneity within the rock, thereby enhancing the applicability and completeness of the findings in real-world scenarios. Additionally, this study focused on the spatial distribution and intensity of rockbursts after excavation, without addressing their temporal evolution. Future investigations may explore how excavation sequencing and timing influence the occurrence of rockbursts. Moreover, given the complex geotechnical environment of the Qinghai-Xizang Plateau, factors such as thermal gradients and pore pressure should be incorporated into extended models in subsequent studies. The rockburst risk identification method proposed in this study demonstrates strong engineering adaptability.