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

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

Add a External Stress feature 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, or Hardening Soil.

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 any material in the model has a temperature dependent mass density, 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.

When using Common model input, you can see or modify the value of the volume reference temperature by clicking the Go To Source button (). This will move you to the Common Model Inputs node under Global Definitions in the Model Builder. The default value is room temperature; 293.15 K.

If you want to create a model input value which is local to your current selection, click the Create Model Input button . This will create a new Model Input node under Definitions in the current component, having the same selection as in the current node.

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, 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, Void ratio at reference pressure for destructured clay erefd, Additional void ratio at initial yielding Δei, and Critical effective 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.

The defaults for the Shear modulus G, Density ρ, Swelling index for changes in suction κs, Compression index at saturation λ0, Angle of internal friction φ, Weight parameter w, Soil stiffness parameter m, Plastic potential shape parameter bs, Tension to suction ratio k, 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, the Reference pressure pref, and the Initial consolidation pressure pc0.

The defaults for the Reference stiffness for primary loading E50ref, Reference stiffness for unloading and reloading Eurref, Elastoplastic compression modulus Kc, Poisson’s ratio ν, Density ρ, Stress exponent m, Cohesion c, Angle of internal friction φ, Dilatation angle ψ, 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 Failure ratio Rf, the Reference pressure pref, and the Initial consolidation pressure pc0.

Select the Include dilatancy cut-off 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.

If a study step is geometrically nonlinear, the default behavior is to use a large strain formulation in all domains. Select the Force linear strains check box to always use a small strain formulation, irrespective of the setting in the study step.

When a geometrically nonlinear formulation is used, the elastic deformations used for computing the stresses can be obtained in two different ways if inelastic deformations are present: additive decomposition and multiplicative decomposition. The default is to use multiplicative decomposition. Select Additive strain decomposition to change to an assumption of additivity.

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

Physics tab with Solid Mechanics selected:
Domains>Material Models>Elastoplastic Soil Material