Abstract: The numerical manifold method is a new developed numerical method and has been used in many fields of geotechnical engineering. But there is no research on numerical manifold method in creep. In recent years, the study of high-order manifold method shows that using high-order cover function could improve accuracy of manifold method in complex geotechnical engineering. The research on high-order numerical manifold method in creep is presented. The “time step-initial strain” method is combined with high-order numerical manifold method to simulate the creep of rock. Based on generalized Kelvin model, some relation equations are given; and a new code is developed. Some examples are used to check the feasibility and rationality of the method. The result shows that the high-order numerical manifold method could simulate the creep of viscoelastic rock very well combining with “time step-initial strain”. It can improve accuracy of the solution only by using high-order cover function but without changing the mesh density.

Key words: high-order numerical manifold method, viscoelasticity, creep, time step-initial strain