Numerical Modeling of Stand-Up Time of Tunnels Considering Time-Dependent Deformation of Jointed Rock Masses

The mechanical responses of tunnels are time-dependent due to creep deformation of rock masses, which can result in large deformations on tunnel walls over time and influence excavation stability. This study investigates time-dependent deformation behaviors of tunnels excavated in jointed rock masses. The creep deformations of both rock and joints are considered using a creep model for jointed rock masses implemented in a distinct-element method code. Simulations of the time-dependent deformation behavior of tunnels are conducted using two-dimensional plane strain models based on the convergence-confinement analysis method. The weakening of the rock mass in a cross-section in an excavated tunnel due to time-dependent deformation of rock mass is simulated using the internal pressure reduction method. Stand-up times of tunnels excavated in jointed rock masses with different rock mass qualities and unsupported roof spans are simulated. The simulation results agree with field data, which validates the effectiveness of the analysis approach used. The analysis approach provides a useful tool for improving the understanding of time-dependent deformation behavior of tunnels. Highlights Time-dependent deformation of rock mass near the tunnel face is simulated using a creep model for jointed rock mass implemented in UDEC. The weakening of face-effect due to time-dependent deformation of rock mass can be analyzed using the convergence-confinement and the internal pressure reduction methods. Stand-up times of unsupported tunnels in joined rock masses are simulated. The simulated stand-up times agree with Bieniawski’s field data.