Plasticity Drucker - Prager Model

The yield criterion can be defined as:

where a and k are material constants which are assumed unchanged during the analysis, s m is the mean stress and s is the effective stress. a and k are functions of two material parameters f and c obtained from experiments where f is the angle of internal friction and c is the material cohesion strength.

Drucker-Prager model can be used to simulate the behavior of granular soil materials such as sand and gravel. In using this material model, the following considerations should be noted:

• Strains are assumed to be small.

• Problems with large displacements can be handled provided that the small strains assumption is still valid.

• The use of NR (Newton-Raphson) iterative method is recommended.

• Material parameters f and c must be bounded in the following ranges:

• • 90 >= f >= 0 (in degrees)  (>= means greater than or equal to)

  • c >= 0 (in force/unit area)

• For most soil mechanics problems, gravitational acceleration can have significant effect, therefore gravitational acceleration should be defined through the GravityPropertyManager.

The required inputs include the following:

•  EX and NUXY

• COHESN = Material cohesion strength

• FRCANG = Friction angle

The Drucker-Prager model can be used with the solid elements (draft and high quality mesh).