When initial density and confining pressure of non-cohesive soil are considered in Pastor-Zienkiewicz (PZ) constitutive model

multiple sets of parameters are required to simulate the same type of material. Thus this model is pretty difficult to be applied in practice

which to a great extent limits its development. To solve the existing deficiency of the PZ model

some recently proposed state parameters are introduced into the dilatancy formula

plastic potential direction vector

loading (unloading) direction vectors and plastic modulus equation of the original PZ model

separately. It is found that the predicting capability of the modified model has been improved in terms of mechanical behaviour of the non-cohesive soil

particularly by considering the initial density and confining pressure. Then the calibrating method for each parameter in the modified model is discussed in detail and the physical meaning of each parameter is further clarified

according to a practical example. Finally

the predictive ability of the modified model is verified by the experimental data. It is shown that predicted results are in good agreement with experimental data

which indicates the modified model is reasonable and feasible.