A novel damage-based creep model considering the complete creep process and multiple stress levels

To develop a unified creep model, the complete creep process of rock is divided into the deceleration region and acceleration region based on the typical deformation characteristics and mechanism of the rock creep behavior. By introducing the time-hardening theory and the damage theory, the analytical solutions of creep strengthening and weakening behaviors during the complete creep process are obtained. A unified creep model has been established that can fully capture all the typical creep behavior stages for rock under multiple stress levels, including instantaneous elastic deformation, decelerating creep, stable creep, accelerating creep, and final failure. The model has the advantages of a simple form and easy access to parameter determination. The parameter determination methods are discussed, and the performance of the proposed model has been verified by comparing the predicted creep strain curves with the experimental results from various rock tests.