Coupled analytical solutions for deep-buried circular lined tunnels considering tunnel face advancement and soft rock rheology effects

For tunnelling in a deep soft rock mass, rock rheology and the advancing process significantly affect the induced pressures on the support system and the long-term safety of the tunnel. In this study, coupled analytical solutions, which take both the rock rheology and tunnel face advancement effects into consideration, are proposed to predict the mechanical behavior of deep-buried circular lined tunnels in a soft rock mass. To account for different rheological behaviors of rocks, five types of viscoelastic models are adopted in the theoretical derivations. The analytical solutions are validated by comparing the predicted results with corresponding existing solutions and those predicted by finite difference simulations. According to parameter degradation, the proposed solutions can be simplified to the classic viscoelastic solution without consideration of tunnel face advancement and the elastic solution with consideration of tunnel face advancement. Based on the proposed coupled solutions, the characteristics of convergent displacements of unlined tunnels with or without consideration of the tunnel face advancement, are studied. In addition, for lined tunnels, the influences of the initial stress release parameter, influence radius of the tunnel face, excavation rate and liner installation time on rock stress and displacement and support pressure are systematically investigated. Finally, the proposed solution is successfully applied to analyze the time-dependent behavior of the Lyon-Turin Base Tunnel, and good agreements are achieved between the theoretically predicted values and corresponding field monitoring data.