A Study of Uniaxial Acoustic Emission Creep of Salt Rock Based on Improved Fractional-Order Derivative

Aiming at the disadvantage that the traditional creep model cannot describe the nonlinear creep acceleration stage (third-order creep stage) of rock. This paper explains the creep process of salt rock from a microscopic perspective based on the Riemann–Liouville type fractional-order calculus operator theory and acoustic emission (AE) theory, and describes the creep process of salt rock with the improved fractional-order derivatives. The results of uniaxial creep damage tests on rock salt specimens under quasi-static loading conditions are given, complete creep damage curves are obtained, and a creep model based on fractional-order derivatives for viscoelastic damage of salt rock is proposed, and finally, the best variable values are fitted to determine the optimum values. The AE characteristic parameter curves were compared with the creep strain curves, and it was found that the AE characteristic curves could predict the time point when the salt rock enters the accelerated creep stage in advance. According to this time point, the model is fitted in sections and compared with the experimental results. The predicted value of the model is in good agreement with the test results, and can better describe the nonlinear accelerated creep stage of salt rock. It is believed that the fractional-order model can simulate the whole process of rock creep well and has good practical application value.