Material parameters of D-P yield criterion in 3D stress space based on non-associative flow rule

Drucker-Prager (D-P) yield criterion was widely used in the FEM (Finite Element Method) analysis of geotechnical engineering in present. For limitation of complex characteristic of geotechnical material, the results of analysis that used D-P criterion do not meet for the practical engineering sometimes. According to the potential theory of plasticity in geotechnical plastic mechanics, the plastic volumetric strain factor (alpha(u)) and the rate of plastic shearing strain to plastic volumetric strain (beta) are advanced. The total plastic strain of frication material is expressed as two kinds of plastic strain caused by the deviatoric stress and spherical stress respectively. alpha(u) and beta considered the level of plastic deformation caused by the invariant of the deviatoric stress and spherical stress. At the same time, beta also reflects the plastic strain coupling of the deviatoric stress invariant and the spherical stress invariant for the different material and different loading level on the view of macroscopic. Submitting the alpha(u) and beta into two yield surface criterion, the material parameters of D-P in 3D stress space are built. Comparing with the material parameters of different solutions, it shows that the plastic deformation is relative to alpha(u), beta, cohesion (c), internal frication angle (phi) and the angle of stress direction (theta) and it fits for the deformation characteristic of geotechnical material.