Investigation into the Construction Response of Tunnels through Fault: Model Test

Abstract

The fractured zone poses a significant risk to construction safety and structure durability in tunnel engineering. However, the effect of excavation methods has not been thoroughly investigated in previous studies. This paper presents a series of 1:30 scale 3D model tests on fault tunnels under the coupling effect of different fault dip angles and construction steps. We measured and analyzed the rock mass deformation and lining structure stress to explore the influence of tunnel excavation by the CD method. The model test results were verified by numerical simulation using the prototype tunnel parameters. Our results show that steeper fault dips correspond to greater radial pressure of the surrounding rock, and pressure in both haunt positions changes more significantly than that in the vault position, while pressure in the side-wall position changes only slightly. Additionally, considerable deformation can be observed in the vault and both haunt positions, with a rock mass relaxation range of less than 1.0 D. For the lining structure stress of each point in the second excavation cycle, larger lining stress is measured in the case of a fault dip of 75° than that in cases when the fault dip equals 45° and 60°, respectively. The biggest stress is observed in the side-wall position after the mid-partition is mantled to form a closed-loop lining structure. Overall, our findings provide valuable insights into the construction response of tunnels through faults and highlight the importance of considering excavation methods in tunnel engineering.