Mechanical behaviour of a large-span double-arch tunnel

A scaled physical model test and numerical simulations of a shallow-buried double-arch tunnel, the Great Wall Ridge Tunnel (GWRT), are performed as a first step toward a full understanding of the deformation of double-arch tunnels in shallow formations. The instrumentation of the model experiment includes high-accuracy dial gauges, miniature stress sensors, and strain gauges to record the mechanical responses of the tunnel supporting system and the surrounding rocks. The experiment strictly follows the designed excavation procedure planned for the GWRT, and the results show good agreement with those obtained from numerical simulations. We focus on the accurate approximation of the ground movement in order to ensure the safety of a neighbouring ancient relic, the Great Wall of the Qi. We also investigate the stress distributions of the surrounding rock formations and the middle wall. Based on the settlements of the ground and the plastic zone distribution, we conclude that the current design of the GWRT construction could potentially damage the neighbouring historical site.