A nonlinear creep constitutive model of rock based on the law of conservation of energy

In order to further explore the creep characteristics of rock under different confining pressure conditions, a series of rock triaxial creep tests are carried out to systematically study the creep behavior of rock under various confining pressure levels. The long-term strength of rock is determined according to the isochronous stress–strain curve, and the relationship between confining pressure and long-term strength is analyzed. Based on the energy principle and strain energy function, an energy nonlinear creep model is established. The test results show that the model effectively describes the full-stage creep behavior of rock under different confining pressures in a concise form and clear physical meaning. Compared with the experimental data, the proposed model has high accuracy and reliability and can better capture the nonlinear characteristics of rock creep under the influence of confining pressure. The method of dividing creep stages according to energy is also suitable and feasible. The test curves of different types of rocks are in good agreement with the model curves, and the correlation coefficients are all above 0.90. The research results provide a theoretical basis and practical model for further understanding the long-term deformation behavior of rock under a complex stress environment and the long-term stability analysis of rock engineering.