Mechanical Behaviors and Structure Safety of a Tunnel Crossing a Water-Rich Fault Fracture Zone—A Case Study

To study the potential disasters caused by tunnels crossing water-abundant fault areas, this study takes the Jinyunshan Tunnel as an example, and studies the groundwater flow law between different rock layers, the interaction between surrounding rock hydrostatic pressure and soil pressure, and the mechanical features and safety of the lining during construction by combining field tests and finite element simulation analysis. The results show that the displacement change rate of the tunnel vault reaches 2.8 mm/d, and the maximum earth pressure and hydrostatic pressure are 2.3 MPa and 1.15 MPa, respectively, both at the bottom of the tunnel in section II. When the tunnel enters the fault fracture zone from the V surrounding rock, the bending moment of the lining increases by 222.78% at the left haunch and 60.87% at the bottom of the right wall. The axial force of the right spandrel increases by 2579.2%, and the left spandrel increases by 221.18%. The safety factor of the two sections is greater than 2.4, indicating that the overall structure is in a safe state, but the safety factor of the second right shoulder is 2.54, which is close to the safety threshold of 2.4. The research results provide a basis for the safety design and construction safety of tunnels through water-rich sections in similar fault fracture zones, and provide a reference for reducing groundwater loss and protecting ecological vegetation.