In the Soil Plasticity subnode you define the properties for modeling materials exhibiting soil plasticity.
Soil Plasticity can be used together with
Linear Elastic Material and
Nonlinear Elastic Material. It is available with the Geomechanics Module.
Soil Plasticity is available for 3D, 2D, and 2D axisymmetry.
Select the Material model —
Drucker–Prager,
Mohr–Coulomb,
Matsuoka–Nakai, or
Lade–Duncan. Most values are taken
From material. For
User defined choices, enter other values or expressions.
In the standard Drucker–Prager formulation, the material parameters are given in terms of the α and
k coefficients. Often material data is expressed in the parameters
c and
ϕ used in the Mohr–Coulomb model. You can then choose to use there parameters instead. If so, select the
Match to Mohr–Coulomb criterion check box (see
The Mohr–Coulomb Criterion). If this check box is selected, the default values for
Cohesion c and the
Angle of internal friction ϕ are taken
From material.
If required, select the Use dilatation angle in plastic potential check box. If this check box is selected, then enter a value or expression for the
Dilatation angle ψ. Alternatively, select
From material. The dilatation angle replaces the angle of internal friction when defining the plastic potential.
If the Match to Mohr–Coulomb criterion check box is
not selected, then the default
Drucker–Prager alpha coefficient and
Drucker–Prager k coefficient are taken
From material.
If required, select the Include elliptic cap check box. Select from the list the hardening model. When
Perfectly plastic (no hardening) is selected, enter values or expressions to define the semi-axes of the ellipse under
Elliptic cap parameter pa and
Elliptic cap parameter pb. When
Isotropic hardening is selected from the list, the default
Isotropic hardening modulus Kiso, the
Maximum plastic volumetric strain εpvol,max, and the
Ellipse aspect ratio R are taken
From material (see
Elliptic Cap with Hardening). Enter a value or expression to define the initial semi-axis of the ellipse under the
Initial location of the cap pb0.
The default Angle of internal friction ϕ and
Cohesion c are taken
From material.
If required, select the Use dilatation angle in plastic potential check box. If this check box is selected, then enter a value or expression for the
Dilatation angle ψ. Alternatively, select
From material. The dilatation angle replaces the angle of internal friction when defining the plastic potential.
Under Plastic potential select either
Drucker–Prager matched at compressive meridian,
Drucker–Prager matched at tensile meridian, or
Associated.
If required, select the Include elliptic cap check box. Select from the list the hardening model. When
Perfectly plastic (no hardening) is selected, enter values or expressions to define the semi-axes of the ellipse under
Elliptic cap parameter pa and
Elliptic cap parameter pb. When
Isotropic hardening is selected from the list, the default
Isotropic hardening modulus Kiso, the
Maximum plastic volumetric strain εpvol,max, and the
Ellipse aspect ratio R are taken
From material (see
Elliptic Cap with Hardening). Enter a value or expression to define the initial semi-axis of the ellipse under the
Initial location of the cap pb0.
If required, select the Match to Mohr–Coulomb criterion check box. If this check box is selected, the default
Angle of internal friction ϕ is taken
From material.
If the Match to Mohr–Coulomb criterion check box is
not selected, then the default
Matsuoka–Nakai mu coefficient μ is taken
From material.
If required, select the Match to Mohr–Coulomb criterion check box. If this check box is selected, then enter a value or expression for the
Angle of internal friction ϕ. Alternatively, select
From material.
If the Match to Mohr–Coulomb criterion check box is
not selected, then the default
Lade–Duncan k coefficient k is taken
From material.
This section is only available with the Drucker–Prager and
Mohr–Coulomb models
If required, select either None,
Mean stress cutoff, or
Principal stress cutoff.
When Mean stress cutoff is selected from the list, enter a value or expression for the
Maximum mean stress σm. Use this to constrain the soil plasticity model with an extra yield surface which limits the maximum pressure in tension.
When Principal stress cutoff is selected from the list, enter a value or expression for the
Maximum tensile stress σt. Use this to constrain the soil plasticity model with an extra yield surface, which limits the maximum principal tensile stress.
The default is None. Select
Implicit Gradient to add nonlocal regularization to the equivalent plastic strain. Enter a value for the:
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Length scale, lint. The length scale should not exceed the maximum element size of the mesh.
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Nonlocal coupling modulus, Hnl. This stiffness is the penalization of the difference between the local and nonlocal variables. A larger value enforces the equivalent plastic strain εpe to be closer to the nonlocal equivalent plastic strain εpe,nl.
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This section is available with the Implicit gradient nonlocal plasticity model. Select the shape function for the
Nonlocal equivalent plastic strain εpe,nl —
Automatic;
Linear;
Quadratic Lagrange, Quadratic serendipity;
Cubic Lagrange, Cubic serendipity;
Quartic Lagrange, Quartic serendipity; or
Quintic Lagrange. The available options depend on the order of the displacement field.
To display this section, click the Show More Options button (
) and select
Advanced Physics Options in the
Show More Options dialog box.
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Deep Excavation: Application Library path Geomechanics_Module/Soil/deep_excavation
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Select the Local method to solve the plasticity problem —
Automatic or
Backward Euler. When
Backward Euler is selected, it is possible to specify the maximum number of iterations and the relative tolerance used to solve the local plasticity equations. Enter the following settings:
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Maximum number of local iterations. To determine the maximum number of iteration in the Newton loop when solving the local plasticity equations. The default value is 25 iterations.
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Relative tolerance. To check the convergence of the local plasticity equations based on the step size in the Newton loop. The final tolerance is computed based on the current solution of the local variable and the entered value. The default value is 1e-6.
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To display this section, click the Show More Options button (
) and select
Advanced Physics Options in the
Show More Options dialog box.
Physics tab with Linear Elastic Material or
Nonlinear Elastic Material node selected in the model tree:
