Time-dependent deformations in deep tunnels: Insights into uncertainty and variability of rheological behavior

The uncertainty in determining rock mass properties significantly impacts tunnel stability. Additionally, squeezing conditions worsen tunnel stability, causing the tunnel to gradually converge over time. This paper addresses this issue and investigates the long-term behavior of deep tunnels using both visco-elastic and viscoelasto-plastic models. This study also includes risk-based analyses to offer a quantitative tool for engineering decision-making. Initially, an analytical method is introduced to calculate tunnel convergence in a visco-elastic rock mass. The uncertainty of key parameters that significantly affect tunnel behavior is also considered. Using MATLAB, the probability distributions of tunnel wall deformations over time are determined. The results indicate that, except in one case, the long-term tunnel convergence follows a right-skewed Gamma distribution, especially with a low GSI in both visco-elastic and visco-elasto-plastic models. This suggests that deterministic methods may not be reliable for ensuring the safety of long-term tunnel designs.