Numerical Investigation of the Optimal Construction Sequence of an Actual Super Shallow Large-Span Tunnel

The construction process of super shallow large-span tunnel is quite complicated comparing with the construction technique of regular tunnels; therefore, it is deserved to investigate the optimal construction sequence which determines the schedule and safety management of the tunnel excavation. To address this issue, the optimal excavation procedure of the super shallow large-span tunnel is investigated using numerical analysis in this study, based on a practical tunnel project. First, the analytical finite element model of an actual tunnel structure is established to implement the numerical simulation of different tunnel excavation. Second, some numerical results are analyzed for the selection of the optimal construction excavation, such as the variation rules of the surface settlement, crown displacement and side wall deformation etc. The analytical results show that the ground surface heaves with the tunnel excavated and the crown displacement improves gradually. Finally, the optimal excavation scheme is determined by comparing the deformation of the tunnel structure and the law of surface subsidence.