The Elastoplastic Soil Material feature is used to model stress-strain relationships that are nonlinear even at infinitesimal strains. It is available in the Solid Mechanics interface. This material model requires a Geomechanics Module license (see https://www.comsol.com/products/specifications/). Elastoplastic Soil Material is available for 3D, 2D, and 2D axisymmetry.

By adding the following subnodes to the Elastoplastic Soil Material node you can incorporate other effects:

Add an External Stress node in case you need to define a pore pressure in a porous soil. The Pore pressure pA is user defined by default. The default value is 1 atm, but you can change it to another value or expression for the pore fluid pressure. If there are other physics interfaces (like Darcy’s Law) in the model that make a pressure variable available, such variables will be available in the list.

The Global coordinate system is selected by default. The Coordinate system list contains any additional coordinate systems that the model includes (except boundary coordinate systems). The coordinate system is used when stresses or strains are presented in a local system. The coordinate system must have orthonormal coordinate axes, and be defined in the material frame. Many of the possible subnodes inherit the coordinate system settings.

Select a Material model from the list: Modified Cam-Clay, Modified Structured Cam-Clay, Extended Barcelona Basic, Hardening Soil, or Hardening Soil Small Strain.

All elastoplastic soil models have density as an input. The default Density ρ uses values From material. For User defined enter another value or expression.

If the material has a temperature dependent density or other material property, and From material is selected, the Volume reference temperature list will appear in the Model Input section. As a default, the value of Tref is obtained from a Common model input. You can also select User defined to enter a value or expression for the reference temperature locally.

The Modified Cam-Clay options adds the equations and interface for defining the material properties for the modified Cam-clay soil model.

From the Specify list, define the elastic properties either in terms of Poisson’s ratio or Shear modulus.

The defaults for the Poisson’s ratio ν or the Shear modulus G, Density ρ, Slope of critical state line M, Swelling index κ, Compression index λ, Initial void ratio e0 , and Void ratio at reference pressure eref are taken From material. For User defined enter other values or expressions

Enter a value or expression for the Reference pressure pref, and the Initial consolidation pressure pc0.

From the Specify list, define the elastic properties either in terms of Poisson’s ratio or Shear modulus.

The defaults for the Poisson’s ratio ν or the Shear modulus G, Density ρ, Slope of critical state line M, Swelling index for structured clay κs, Compression index for destructured clay λd, Angle of internal friction ϕ, Initial structure strength pbi, Destructuring index for volumetric deformation dv, Destructuring index for shear deformation ds, Plastic potential shape parameter ξ, Initial void ratio e0, Void ratio at reference pressure for destructured clay erefd, Additional void ratio at initial yielding Δei, and Critical equivalent deviatoric plastic strain edcp are taken From material. For User defined enter other values or expressions.

Enter a value or expression for the Reference pressure pref, and the Initial consolidation pressure pc0.

From the Specify list, define the elastic properties either in terms of Poisson’s ratio or Shear modulus.

The defaults for the Poisson’s ratio ν or the Shear modulus G, Density ρ, Slope of critical state line M, Swelling index κ, Swelling index for changes in suction κs, Compression index at saturation λ0, Compression index for changes in suction λs, Angle of internal friction ϕ, Weight parameter w, Soil stiffness parameter m, Plastic potential shape parameter bs, Tension to suction ratio k, Initial void ratio e0, Void ratio at reference pressure and saturation eref0, and Initial yield value for suction sy0 are taken From material. For User defined enter other values or expressions.

Enter a value or expression for the Initial suction s0, Suction s, the Reference pressure pref, and the Initial consolidation pressure pc0.

Select the Failure criterion — Mohr–Coulomb, Matsuoka–Nakai, or Panteghini–Lagioia.

Select the Mobilized dilatancy angle — Soreide, Rowe, Modified Rowe, Wehnert, Li–Dafalias, Rowe–Li–Dafalias, or User defined.

The Reference initial stiffness for primary loading Eiref, Reference stiffness for unloading and reloading Eurref, Bulk modulus in compression Kc, Poisson’s ratio ν, Density ρ, Stress exponent m, Cohesion c, Angle of internal friction ϕ, Dilatation angle ψ, Ellipse aspect ratio R, and Initial void ratio e0 are taken From material. For User defined enter other values or expressions.

Enter a value or expression for the Failure ratio Rf, the Reference pressure pref, and the Initial consolidation pressure pc0.

Select the Include dilatancy cutoff check box if needed. The defaults for the Maximum void ratio emax is taken From material. For User defined enter other value or expression. Enter a value or expression for the Initial volumetric strain εvol0.

Select the Failure criterion — Mohr–Coulomb, Matsuoka–Nakai, or Panteghini–Lagioia.

Select the Mobilized dilatancy angle — Soreide, Rowe, Modified Rowe, Wehnert, Li–Dafalias, Rowe–Li–Dafalias, or User defined.

The defaults for the Reference initial stiffness for primary loading Eiref, Reference stiffness for unloading and reloading Eurref, Initial shear modulus G0, Bulk modulus in compression Kc, Poisson’s ratio ν, Density ρ, Reference shear strain γ, Stress exponent m, Cohesion c, Angle of internal friction ϕ, Dilatation angle ψ, Ellipse aspect ratio R, and Initial void ratio e0 are taken From material. For User defined enter other values or expressions.

Enter a value or expression for the Failure ratio Rf, the Reference pressure pref, and the Initial consolidation pressure pc0.

Select the Include dilatancy cutoff check box if needed. The defaults for the Maximum void ratio emax is taken From material. For User defined enter other value or expression. Enter a value or expression for the Initial volumetric strain εvol0.

In case of cyclic loading the load reversal points are automatically detected. But in many cases the load reversal points are known a priori. The Load Reversal Points section enables to set the load reversal points manually based on a loading parameter.

The default is None. Select Implicit Gradient to add nonlocal regularization to the equivalent plastic strain. Enter a value for the:

Select a Formulation — From study step (default), Total Lagrangian, or Geometrically linear to set the kinematics of the deformation and the definition of strain. When From study step is selected, the study step controls the kinematics and the strain definition.

To have full control of the formulation, select either Total Lagrangian, or Geometrically linear. When Total Lagrangian is selected, the physics will force the Include geometric nonlinearity check box in all study steps.

Select a Strain decomposition — Automatic (default), Additive, or Multiplicative to decide how the inelastic deformations are treated. This option is not available when the formulation is set to Geometrically linear.

The Strain decomposition input is only visible for material models that support both additive and multiplicative decomposition of deformation gradients.

Select the Calculate dissipated energy check box as needed to compute the energy dissipated by Creep, Plasticity, Viscoplasticity, or Viscoelasticity.

To display this section, click the Show More Options button () and select Advanced Physics Options in the Show More Options dialog box.

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.

Select the Reduced integration check box to reduce the integration points for the weak contribution of the feature. Select a method for Hourglass stabilization — Automatic, Manual, or None to use in combination with the reduced integration scheme. The default Automatic stabilization technique is based on the shape function and shape order of the displacement field.

Control the hourglass stabilization scheme by using the Manual option. Select Shear stabilization (default) or Volumetric stabilization.

When Shear stabilization is selected, enter a stabilization shear modulus, Gstb. The value should be in the order of magnitude of the equivalent shear modulus.

When Volumetric stabilization is selected, enter a stabilization bulk modulus, Kstb. The value should be in the order of magnitude of the equivalent bulk modulus.

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:

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 Solid Mechanics selected: