# Mechanisms of Tunnel Rockburst Development Under Complex Geostress Conditions in Plateau Regions
## 1 Introduction
At present, there are few reports on the development patterns of rockbursts under such complex stress environments, and their disaster characteristics and failure mechanisms remain unclear, making the effective prediction of rockburst risks difficult. Therefore, elucidating the development patterns and occurrence characteristics of rockbursts under the complex stress environments of plateau regions is of great significance for rockburst risk prediction, assessment, and mitigation in plateau tunnel engineering. In view of this, this study takes deep-buried tunnel engineering on the Qinghai-Xizang Plateau, represented by the Sichuan-Xizang Railway, as its application background. Based on numerical simulations using FLAC3D, three key variables--geostress orientation, lateral pressure coefficient, and tunnel depth--that capture the main characteristics of complex geostress environments were selected to systematically investigate their influence on the spatial distribution, intensity, and extent of tunnel rockbursts. This research aims to reveal the development and evolution mechanisms of rockbursts under complex geostress conditions in plateau regions. The findings can provide scientific insights and theoretical support for rockburst risk prediction, construction method selection, and protective design for the Sichuan-Xizang Railway and other major tunnel projects in plateau regions. Specifically, the main contributions of this study are as follows:  
1. Development of automated computation and visualization of key rockburst indicators based on FLAC3D using the FISH language. This study conducts secondary development of FLAC3D via FISH programming to extract, record, and visualize critical parameters such as tangential stress around the chamber, the Russenes rockburst criterion index, and elastic strain energy. Compared with conventional manual post-processing methods, this approach significantly improves simulation efficiency and data traceability, thereby providing a technical foundation for multi-criteria rockburst identification under complex stress environments on the plateau. 2. Systematic evaluation of the influence of complex stress characteristics on the spatial distribution and severity of rockbursts in plateau regions. The study selects three representative variables--stress orientation, lateral pressure coefficient, and burial depth--to characterize plateau-specific stress environments. Through numerical simulation, it analyzes the coupled effects of these parameters on the location, intensity, and affected range of rockbursts, offering new insights into the incubation and development mechanisms of rockbursts under high in-situ stress conditions. 3. Validation of simulation results using a real-world engineering case to enhance model applicability. A typical tunnel section of the Sichuan-Tibet Railway is selected as a case study. The comparison between the simulated rockburst distribution and field observations demonstrates spatial consistency, thereby enhancing the engineering relevance of the research outcomes and providing quantitative support for risk identification and protective design in major plateau tunnel projects.