An improved nonlinear creep damage model of slates considering freeze–thaw damage and bedding damage

To study the creep behavior of bedding slates after freezing and thawing, the RLW-2000 rock creep triaxial instrument was used to carry out the creep test, and the creep curves of slate under different bedding angles and different freeze–thaw cycles were obtained. Then, based on the slate creep test results and the fractional-order theory, a new nonlinear creep damage model considering freeze–thaw damage and bedding damage was proposed. The creep damage model can not only describe the changes in the three creep stages (primary creep, steady-state creep, and accelerated creep) but also reflect the influence of freeze–thaw and bedding coupling damage on creep characteristics. The mathematical optimization analysis software 1stOpt was used to identify the parameters of the nonlinear creep damage model. Finally, the influence of stress level and bedding angle on creep parameters was analyzed, and the creep characteristic parameters in the creep damage model were sensitively analyzed. The consistency between the test data and the predicted results showed that the nonlinear creep damage model proposed in this study can accurately reflect the creep behavior of rock with freeze–thaw and bedding-damaged.