Abstract: To investigate the influence of confining pressure on the creep behavior of rock,creep tests were carried out under various confining pressure conditions.By incorporating a hardening function and a damage variable,a hardening-damage coupled three-dimensional creep model for surrounding rock was established.On this basis,by introducing a yield function and a plastic potential function,the one-dimensional creep relation of sandstone was extended to a three-dimensional form,and the model parameters were identified and validated using experimental data.The results show that the predicted creep curves agree well with the experimental curves overall,with only local deviations in the accelerated creep stage,while the correlation coeffi cients are all greater than 0.90,indicating that the model can effectively describe the whole creep process of rock.Compared with the Nishihara model,the proposed hardening-damage coupled three-dimensional creep model for surrounding rock can not only characterize the coupled evolution of hardening and damage during creep,but also better capture the variation patterns in the decelerating creep,steady-state creep,and accelerated creep stages.The model can provide a theoretical reference for the long-term stability analysis of surrounding rock and geotechnical engineering design.

Key words: rock creep,hardening effect,damage variable,Nishihara model,accelerated creep