Large-scale geo-mechanical model tests for stability assessment of super-large cross-section tunnel

For ensuring safety during the construction and use of a super-large cross-section tunnel, it is essential to understand the lining structure failure pattern and the instability of the surrounding rock mass under a high burial depth. With the Letuan Tunnel of China as an engineering background, we conducted large-scale geo-mechanical model tests and numerical simulations in this study. The results reveal the failure behaviour of the lining structure of a super-large cross-section tunnel and demonstrate the stress variation of the surrounding rock under overload conditions. Based on an analysis of the key protected areas as per the experimental results, the lining structure near the tunnel foot, vault, and entrance should be strengthened, and the stress of the surrounding rock near the middle rock wall, especially the tunnel sidewall and foot, should be focused on. Overloading safety factors were also determined through the overloading test. This study can provide a reliable reference for the design of support structures and safety control during the construction of a double-hole super-large cross-section tunnel in the deeply buried area.