Nonlinear Creep Constitutive Model of Rock Considering Hardening Effect

The creep of rock is a complex mechanical phenomenon driven by internal stress adjustment and the interplay between hardening and damage effects. To precisely capture the nonlinearity of rock creep and the law of accelerated deformation, a hardening function and a damage variable are introduced. Based on traditional rheological models, creep mechanisms, and damage laws, an accelerated creep constitutive model integrating hardening and damage effects is established. This model uses nonlinear functions and physical parameters to describe the coupling of hardening and damage throughout the creep process. The results show that the model can accurately reproduce the entire creep curves of rock specimens under different stress levels, with correlation coefficients exceeding 0.90. Further verification with diverse test data confirms its ability to describe the whole creep process and reflect the hardening–damage mechanisms, enabling accurate prediction of the transition to the failure-prone tertiary creep stage. Overall, this constitutive model provides a more accurate theoretical tool for understanding rock creep, offering significant value for rock engineering design and stability analysis in projects like underground mining and tunneling.