Embedded region

An embedded region ties one-dimensional members to the continuum around them, so that a pile or an anchor can pass through a soil mesh without the two meshes having to share nodes. The member is the guest, the continuum it runs through is the host.

This is what makes it practical to model a pile in soil: the soil is meshed once, and the pile is laid through it.

Each embedded region is a named block. A model may hold several — a pile group needs one per pile, or one for a set of piles sharing the same treatment.

Method

Method is the first choice, and it governs everything below it. The rest of the block changes with it.

Method	What it does
absorbed	The guest nodes are tied rigidly to the host. No relative movement, no interface behaviour
interaction	The guest is connected to the host through a line interaction law, so it can move relative to the soil
interaction surface	As above, but the shaft is treated as a cylindrical surface of given diameter, with its own capacity and an optional base resistance

Absorbed is the simplest and suits members that are cast into the soil. Interaction and interaction surface are for members that can slip, which is the usual case for a pile under working load.

Sets

Every method needs the guest and the host; the other two sets appear only where they apply.

	Set	Assigned to	Shown for
	Guest / embedded element set	Lines	all methods
	Embedded node set	Lines	absorbed
	Host continuum element set	Surfaces, volumes	all methods
	Pile base node set (optional)	Points	interaction surface

The host set must actually enclose the guest. A member running outside the host region has nothing to connect to.

Interaction settings

Shown for the interaction method.

Line interaction law selects the behaviour along the member:

Law	Additional parameters
linear	—
constant	Ultimate axial traction
Mohr-Coulomb	Interface cohesion c, interface friction angle φ, shear surface per unit length A_s

Common to all three:

Parameter	Unit
Axial stiffness k_t	kN/m²
Lateral stiffness k_n	kN/m²

Interaction-surface settings

Shown for the interaction surface method. The shaft is treated as a cylinder rather than a line, which allows a shaft capacity and a base resistance to be given separately.

Shaft

Parameter	Unit
Interaction-surface diameter D	m
Tangential shaft stiffness k_t	kN/m³
Normal shaft stiffness k_n	kN/m³

Pile shaft capacity law is either constant or Mohr-Coulomb.

With constant, a single constant shaft capacity in kN/m² applies over the whole shaft.

With Mohr-Coulomb, the capacity follows the pressure, and three further choices appear:

• Capacity-pressure source — Interface or Soil, deciding where the pressure driving the capacity is taken from.
• Soil-stress recovery — Inverse-distance or Gaussian, how the soil stress is recovered at the shaft. The Gaussian option adds a support factor.
• Limit capacity-effective pressure — when set to yes, a maximum capacity pressure caps it.

Base

Shown when a pile base node set is given.

Base mobilisation law selects how the base resistance develops. Both laws take a base stiffness k_b in kN/m³ and a compressive base capacity σ_lim in kN/m²; the hyperbolic law adds a capacity scaling factor.

Ghost elastic zone

Ghost elastic zone replaces the soil inside the shaft with an elastic material, which prevents the host elements the pile passes through from being distorted by it. It is on by default and takes a Young's modulus and a Poisson's ratio.

Numerical settings

Setting	Meaning
Circumferential points per ring n_p	How finely the shaft surface is sampled around its circumference
Base-disk quadrature points	How finely the base disk is integrated

Raising either improves the resolution of the interaction at the cost of calculation time.

Embedded regions are described under Embedded regions in the numgeo reference manual.