Soil material

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The Soil material dialogue manages soil libraries and lets you define parameters for foundation design and deformation analyses.

Overall layout of the dialogue

The dialogue consists of three main areas:

At the top:

• Find – search materials by typing the name

On the left-hand side:

• Material tree grouped by soil types. This shows both library soils and those already used in the project

On the right-hand side:

• No editable parameters
• Message: “Safety factors can be specified under Foundation design tab, Configure foundation design button.”

At the bottom of the dialogue are library manipulation buttons:

• New – add a new soil material to the library (opens soil-specific dialogue, see below)
• Modify – edit the selected soil material (opens the same dialogue as New)
• Delete – remove the highlighted entry from the library (built-in entries cannot be deleted)
• Import – load a saved .fdsoil library file. Entries with matching names will be ignored, keeping the local material definitions
• Export – save the entire soil material library to an external .fdsoil file

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New material

When you press New or Modify, a dedicated soil material dialogue opens.

Name

• Name – text field for the material name shown in schedules, lists and tooltips

Strength parameters (left-hand side)

Strength properties are colour-coded by their use:

• blue – used in foundation design
• yellow – used in deformation calculation
• green – used in both

• Reference level – numeric field for soil layer depth
• Behaviour – drop-down list: Undrained or Drained
• Design according to combined behaviour – checkbox to combine drained and undrained behaviour
• cuk – characteristic undrained cohesion (with depth-dependence d)
• ck – characteristic cohesion (with depth-dependence d)
• φk – effective friction angle
• φcvk – characteristic constant-volume (critical state) friction angle
• γdry – unit weight in dry state
• γsat – unit weight in saturated state

Depth-dependence (d) fields describe linear variation of the parameter with soil depth. A diagram next to the input illustrates the meaning of d.

Deformation parameters (right-hand side)

The Material model drop-down defines how soil stiffness is represented:

• Linear
• Over consolidated
• Generic

Each model shows a different set of parameters and diagram:

Linear model

• M0 – constrained modulus (with depth-dependence d)
• E – Young’s modulus (with depth-dependence d)
• ν – Poisson’s ratio

info

M0 and E are mutually exclusive – selecting one disables the other.

Over consolidated model

• Mu – constrained modulus at ultimate state (with depth-dependence d)
• M0 – constrained modulus at reference state (with depth-dependence d)
• ML – constrained modulus at limit state (with depth-dependence d)
• M’ – constrained modulus under intermediate load (with depth-dependence d)
• σ’c – effective pre-consolidation pressure (value only)
• ρ’c – corresponding strain (with depth-dependence d)
• σ’L – effective limit pressure (value only)
• ρ’L – corresponding strain (with depth-dependence d)
• ν – Poisson’s ratio

Generic model

• Mu – constrained modulus (with depth-dependence d)
• ν – Poisson’s ratio

Below the two values is a special editable table, allowing you to define stiffness development for arbitrary stress steps:

• σ’ – effective stress
• ρ’ – strain
• ρd – strain increment
• M – modulus
• Md – modulus increment