Accelerated creep model of rock based on energy dissipation theory

The starting condition of the rock accelerated creep stage is a difficult problem in analyzing the whole process of creep. The existing Nishihara model has obvious shortcomings in describing the accelerated creep character-istics of the rock viscoplastic stage. In order to better describe the whole process of rock creep,divide the creep into different stages and characterize the deformation characteristics of accelerated creep stage,the control threshold of ac-celerated creep start was defined based on the energy dissipation theory. A new model of rock ac-celerated creep con-stitutive model was constructed by introducing the Perzyna viscoplastic model into the Nishihara model. The model was verified by a three-axis progressive loading creep experiment. The results showed that the energy consumption and creep damage during creep loading were mainly derived from the internal energy changes inside the geomaterial. The rock accelerated creep model based on energy dissipation theory and considering creep rate changes could better de-scribe the viscoelastic-plastic creep properties of rock. The model not only reflected the relationship between rock ener-gy dissipation and creep variation,but also highlighted the effects of creep rate and creep stress state on accelerated creep. The model overcome the shortcomings of the traditional Nishihara model which was difficult to describe the characteristics of accelerating creep deformation. Also,it more accurately reflected the creep characteristics of the at-tenuation and stable creep stages. The comparative analysis results verified that it was feasible to use the dissipation rate value to define the control threshold from the stable creep phase to the accelerated creep phase. The introduction of the Perzyna viscoplastic model was effective for improving the deformation characteristics of the rock specimen dur-ing the accelerated creep stage of the rock model. The research results provide a new method for analyzing the whole process of creep deformation and the stage of creep deformation,and also provide a new idea for studying creep model and creep mechanics.