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Abstract Based on Nishihara model by introducing the nonlinear Bingham viscoplastic component and adding a Kelvin component，a new nonlinear viscoelasto-plastic rock rheological model(nonstationary Nishihara model) is proposed，which can fully reflect the global rheological property of rock material. Rock viscoplastic rheological parameters nonlinearly change with time under high stress level. According to the UMAT format requirement of ABAQUS and plane strain or stress finite element theory of nonstationary Nishihara viscoelasto-plastic rheological constitutive model，the corresponding UMAT codes are programmed. The numerical test results show that the establishment of nonlinear viscoelasto-plastic rheological model can uniformly describe creep process under different stress states，which demonstrate the extensive adaptability of the model. Using the nonstationary Nishihara viscoelasto-plastic model，the rheological numerical analysis is applied to rock slope. Under the large load on the top of slope，the slope vertex enters into the accelerated creep stage firstly；while the midpoint and end point of slope are under a low stress state or the viscoelastic stage，the displacement tends to be a constant value finally. These results indicate that the developed model is correct and reliable，and will have good application prospects.
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Received: 04 March 2010
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2011, Vol. 30 
