Abstract:

To address the secondary lining cracking caused by creep in water-rich surrounding rock of the Yanglin Tunnel, an established hydro-mechanical coupled creep model for rock was adopted and embedded into numerical software via secondary development. The convergence-confinement method and orthogonal tests were employed to determine an optimized support scheme for the cracked section, and field monitoring was conducted during construction. Subsequently, the programed model was used to perform hydro-mechanical coupled numerical simulations of the tunnel section under the new support scheme to assess its long-term stability. The results indicate that: (1) secondary lining cracking is attributable to the combined effects of unsymmetrical loading induced by inclined shale interlayers in composite strata and the creep behavior of carbonaceous mudstone; (2) the new support scheme significantly reduces surrounding rock displacement, crown settlement, and convergence rate, with displacements eventually converging and stabilizing, demonstrating satisfactory performance in engineering application; (3) the simulation results derived from the secondary development model are in good agreement with field measurements, validating the model's rationality and accuracy in simulating creep processes during tunnel construction. This study provides a reference for tunnel support optimization and long-term stability assessment in similar water-rich creep strata.

Key words: composite stratigraphic section, hydro-mechanical coupling, creep characteristics, support optimization, convergence-confinement method, secondary development