Generally

curves of rock creep include three stages: attenuation creep stage

steady creep stage and accelerated creep stage. The traditional models for rock creep

which always contain Newtonian dashpot rather than non-Newtonian dashpot

couldn’t describe accelerated creep stage. An improved constitutive model for rock creep is proposed; and the method can be divided into three steps. First

traditional Kelvin model is not quantitatively good in description of initial attenuation creep stage and steady state creep stage. A modified Kelvin model using non-Newtonian dashpot is used here in. The power-law creep function is obtained by solving the constitutive relation. Second

the parallel connection of non-Newtonian dashpot and plastomer

whose creep function is power function

is used for description of accelerated creep. Third

by connecting instantaneous elasticity Hooke body

modified Kelvin and nonlinear viscoplastic body in series

a new visco-elastoplastic constitutive relation of rock is proposed. This creep model can describe attenuation creep stage

steady-state creep stage and accelerated creep stage. It is shown that creep testing curves under different conditions are coincident well with the theoretic curves; and the model is reasonable and feasible.