Assign element type

The element type decides which balance equations are solved on a part of the model, and how the element is integrated. It is assigned before the material, because it determines what the material has to provide: a two-phase element needs a permeability, a single-phase element does not.

The branch has two entries.

Continuum

Assigned to surfaces and volumes — the soil and rock of the model.

Formulation selects the balance equations:

Formulation
Single-phase solid
Single-phase porous
Two-phase u-p
Two-phase u-p - stabilised
Two-phase u-p-U
Two-phase u-U
Three-phase u-p
Three-phase u-p - stabilised
Three-phase u-p-p
Flow-only

A single-phase element solves the mechanical problem only. A two-phase element solves the deformation of the soil skeleton together with the flow of pore water, and a three-phase element adds pore air. Flow-only solves the flow problem without a mechanical part.

The formulation must match the number of phases of the material assigned to the same region.

Integration selects the numerical integration scheme:

Option	Meaning
full	Every integration point of the element is used
reduced	Fewer points, e.g. one for a four-node quadrilateral

Reduced integration avoids volumetric locking, but allows zero-energy deformation modes that need suppressing — see Hourglass stiffness in the material manager.

Truss/Beam

Assigned to lines — the structural members of the model.

Formulation is either Truss or Beam. A truss carries axial force only; a beam also resists bending, shear and torsion. There is no integration setting.

The choice here must match the element type of the section assigned in the truss/beam material manager.

The element formulations are described under Elements in the numgeo reference manual.