Abstract: Based on the theory of generalized plasticity， for static Pastor-Zienkiewicz(P-Z) model parameters， it can be divided into eight parameters from three aspects. The sensitivity analysis of vertical displacement varying with each parameter was performed. The results showed that elastic modulus E exhibits the largest sensitivity， and the corresponding maximum rate of vertical displacement is 66.05%， when the every parameter is changed between -40%~40%. Followed by the angle of internal friction φ and Poisson’s ratio μ， the rate of vertical displacement was within ±10%. But for the parameters about plastic modulus， the rate of vertical displacement was less than ±1%. When lack of measured data， the values of plastic parameters can come from a great amount of geological data. The conclusions can provide important basis for the selection of P-Z sandy model parameters in the deformation calculation of sub grade.

Key words: Pastor-Zienkiewicz model, model parameters, vertical displacement, rate of change, sand