A nonlinear creep model for transversely isotropic rock based on fractional calculus theory.

A nonlinear creep model based on fractional calculus theory is proposed to better describe the creep characteristics of transversely isotropic rock. The model includes a Hooke elastomer, a fractional Abel dashpot, a Kelvin body, and a nonlinear viscoplastic body, which effectively capture the three stages of creep (including the primary, steady-state, and accelerating creep stages) while also reflect the influence of different bedding angles on creep behavior. The parameters of the model are identified by the Levenberg–Marquardt algorithm. Compared to previous models assuming constant Poisson's ratio for transversely isotropic rock, our nonlinear creep model demonstrates improved accuracy and rationality. [ABSTRACT FROM AUTHOR]