A Meso/Macroscale Theoretical Model for Investigating the Large Deformation of Soft Rock Tunnels Considering Creep and Anisotropic Effects.

The rheological deformation of soft rock resulting from tunnel excavation can lead to significant construction and safety challenges. In this study, a multiphase numerical model was developed to simulate the rheological deformation of soft rock surrounding a tunnel after excavation. The developed model considers the coupled meso/macroscale creep and damage processes of the rock using the coupled discrete element method–finite element method (DEM–FEM). In particular, the damage and deformation accumulation at the mesoscale (i.e., initial phase before excavation, loading phase due to the disturbance of the excavation and creep-induced damage phase leading to large deformation) were incorporated into the model. The model predictions were validated using field monitoring data. By incorporating the coupled meso/macroscale deformation process of the rock into the model, the predicted time-dependent displacements of the tunnel face agree reasonably well with the monitoring data. In addition, the results demonstrate that tunnel brittle damage accumulated in mineral clusters severely leads to instantaneous deformation, which becomes less important in the creep evolution stage. Furthermore, the results indicate that the final deformation is characterized by a high sensitivity to the value of mesoscale modeling parameters. Highlights: A multiphase numerical model was developed to simulate the rheological deformation of soft rock surrounding a tunnel after excavation. The developed model considers the coupled meso/macroscale creep and damage process of the rock using the discrete element–finite element coupling method (DEM–FEM). By incorporating the coupled meso/macroscale deformation process of the rock into the model, the predicted time-dependent displacements of the tunnel face agree reasonably well with the monitoring data. Bedding joints were considered in the model, and the influences of joints on the local movement of grains as well as the final converged deformation were assessed. The influences of mesoscale tensile strength, mesoscale cohesive strength and the fraction of grains experiencing creep on macroscale deformation were discussed. [ABSTRACT FROM AUTHOR]