Failure mechanism of deep-buried tunnel surrounding rock-lining system: physical model tests and numerical investigation

Abstract

Lining cracking is a common failure mode in tunnel construction and operation, particularly in regions characterized by unfavorable geological conditions (e.g., weak strata), which poses significant risks to tunnel stability. This study conducted dynamic physical model tests to investigate the failure mechanisms associated with tunnel excavation within weak geological environments. During the excavation process, the deformation of surrounding rocks comprises both instantaneous and creep deformations. Utilizing similarity theory, the time-dependent creep behavior of tunnels under constant loading conditions was examined. A strain acquisition system alongside a digital photogrammetry system was employed to monitor the mechanical responses of both surrounding rocks and linings, thereby elucidating the evolution characteristics of failures during excavation. The test results indicate that stress concentration and redistribution occur in surrounding rocks post-excavation, leading to abrupt changes in strain. Following lining installation, both stress and strain fields within the cavern gradually stabilize. Notably, the rock-lining system significantly contributes to long-term tunnel stability. Subsequently, a nonlinear creep model capable of accurately describing rock creep behavior was proposed, and numerical analysis utilizing finite difference methods was performed to explore deformation mechanisms during excavation processes, revealing that failure characteristics observed in surrounding rocks align well with experimental findings.