Shear creep damage model for rocks under acidic freeze-thaw cycles and its software application

To investigate the influence of acidic freeze-thaw cycles on the creep behavior of tunnels in cold regions, shear creep tests were conducted on granite from the Huibai Tunnel in Jilin Province. The creep deformation characteristics and meso-damage mechanisms of the rock were systematically analyzed. Based on the experimental rules, the coupling damage variables of acidic freeze-thaw and loading were defined, and a shear creep damage model that can describe the entire creep process of rock under acidic freeze-thaw cycles is established. The proposed model was reformulated into a three-dimensional finite difference form and implemented in the 3DEC platform via C++ secondary development. The validity of the proposed model and its numerical implementation was verified through degeneration analysis and experimental data. Subsequently, the developed model was applied to numerically assess the long-term stability of tunnel surrounding rock in cold regions. The results show that: (1) Acidic freeze-thaw cycles significantly aggravate the creep damage of granite. As the number of cycles increases, the creep deformation and creep rate rise progressively, the transition to the accelerated creep stage shifts to earlier times, and the failure stress exhibits a decreasing trend. (2) The implemented shear creep damage model accurately captures the complete creep process of rock under acidic freeze-thaw cycles, confirming its validity. (3) Furthermore, as the acidic freeze-thaw cycles increases, the creep deformation and plastic zone range of the tunnel gradually increase, and the maximum values consistently concentrated in the crown area. The findings of this study can provide a theoretical basis for the long-term stability evaluation of surrounding rock and disaster prevention in cold-region tunnels.