Abstract: To ensure the safety and normal usage of geotechnical engineering, it’s necessary to analyze the creep of rock mass. The “time step-initial strain” method is commonly used to compute the creep of rocks. Numerical manifold method (NMM) is a recently developed numerical method which is used to simulate the deformation of jointed rock mass but has not been used to analyze the creep of rocks. A "time step-initial strain" computing module has been added to the NMM code. The result of simulating the deformation of generalized Kelvin model shows that the new program can reflect the trend of viscoelastic creep of rocks and could be used to simulate the creep strain of jointed rock mass; so the adapted NMM now can compute both linear elastic and viscoelastic deformation of rock mass. It reflects rocks’ deformation trend more comprehensively, and extends the usage scope of NMM in geotechnical engineering.

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