In order to investigate the mechanical properties of face-based mixed milling planes and their ontological model that is not unspecified yet. Based on the triaxial test， a nonlinear shear expansion constitutive model was constructed based on the Duncan-Chang model and the Pastor-Zienkiewicz shear expansion equation， and the stiffness matrix of this constitutive model was derived by applying the theory of infra-elasticity. Moreover， the model was developed twice with the help of the UMAT subroutine of the ABAQUS finite element software platform， which verified the model accuracy and reliability of the model. In addition， the overall sensitivity analysis and the response surface analysis of the key parameters of the model were also carried out. The results show that at about 10% axial strain， the strength of the two materials gradually reaches the residual strength under different circumferential pressures， and the volumetric strain and axial strain show a tendency to decrease and then increase， and exhibit obvious shear expansion characteristics within a certain range. The triaxial tests were simulated using a second developed UMAT subroutine， and the results showed a high degree of agreement when compared to the test results. The study index deviatoric stresses （σ1-σ3） are particularly affected by the parameters φ0，