By means of stepwise incremental cycling loading and unloading

the test of siltstone specimen was done under uniaxial condition.The test results show that the siltstone possesses characteristics of instantaneous elasticity

decay

stable creep

etc.stages.The MCVISC creep model was set up which can overall reflect these properties through improved Nishihara model

and the creep constitutive model of finite difference form for three-dimensional state was deduced.Using second development program interface of FLAC3 Dwith the Visual C++language

the program of user-defined model was developed

and the program flowchart and the key technique of code compiling were given.At the same time

the correctness and reliability of program compiling were verified through cases.The results show that numerical simulating result coincides with test one for either strain level or overall tendancy of creep

which indicates that the developed model is effective and feasible.