Failure Behavior of Tunnel Inverted Arch Structure in Carbonaceous Slate Stratum: A Case Study

This study investigates the failure behavior of the inverted arch structure in carbonaceous slate stratum. The cracks of the inverted arch are observed in this tunnel, and they are caused by the large deformation of the rock mass. To reveal that the large deformation caused by the expansion of surrounding rock when encountering water is the main factor leading to cracking. An extended finite element method model is established based on the extended Drucker–Prager yield criterion, which allows simultaneous volume increase through non‐associated flow. Four cases with different dilatancy angles are analyzed to present the cracking behavior and rock plastic zone distribution. The numerical results demonstrate that lower dilatancy angles led to more significant crack propagation and larger plastic zones at the tunnel bottom. The installation of anchor bolts is studied as the reinforcement method against the uplift of the rock mass around the inverted arch. The numerical results demonstrate that 4 m anchor bolts with a 90° setting direction can achieve the economical and effective reinforcement effect. This study provides an effective strategy for numerical modeling of expansive surrounding rock and offers practical recommendations for optimizing tunnel support strategies in carbonaceous slate stratum.