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Soil Properties

To define soil properties:

  1. Select Soil Properties Soil Properties icon from the toolbar or the Soils menu.
  2. Enter the soil properties in the Soil Properties dialog. For each material:
    • Enter the soil name and unit weight.
    • Enter the k0 for the soil (used for calculation of horizontal xx and yy geostatic stress).
    • Enter Poisson's ratio if applicable (see below for details).
    • You can use the checkboxes to enable or disable the input for Immediate Settlement, Primary Consolidation or Secondary Consolidation. If a checkbox is selected, then the corresponding settlement type will be computed for that material. If a checkbox is NOT selected, then the corresponding settlement type will not be computed for that material.
    • Specify Datum Dependency, if applicable.
    • If you need assistance with input data values, you can select the Pick Pick icon button which is available beside the input edit box for most material parameters (see below for details).
    • If you are using the Multiple Layer stress computation method, then you can define the elastic modulus of the soil by selecting the Layer Modulus button (see below for details).
    • You can specify undrained shear strength parameters by clicking on the Undrained Shear Strength button
    • If your model includes Wick Drains, you can define horizontal flow parameters by selecting the Wick Drains button (see below for details).
    • If your model includes Liquefaction, you can define the Fines Content (%) and D50 values by selecting the Liquefaction button. (see below for details).
  3. When you are finished defining soil properties, select OK in the Soil Properties dialog.

After soil properties have been defined, the properties are assigned to the soil layers of your model in the Soil Layers dialog.

For detailed information on the soil properties and their implementation, definitions and typical values, see the following documents:

Poisson's Ratio

Although Poisson's Ratio can always be entered in the Soil Properties dialog, it is only applicable if you are using one or more of the following analysis options in Settle3:

If you are not using any of the above options, then Poisson's Ratio will have no effect on the analysis (e.g. if you are using Boussinesq stress computation, considering vertical stress only, and using flexible loads, Poisson's Ratio does not enter into the analysis).

NOTE: the staging of the Poisson ratio is valid for regular loads only. The Poisson ratio cannot be staged with embankment loads.

Datum Dependency

To define properties which vary by depth, go to the Datum Dependency tab and check the option on.

You can turn on datum-dependency for any defined parameter. Three datum methods are available: Bottom, Rate of Change, and Rate of Change with Cutoff.

Bottom

In this case, all applicable parameters can have a Top and a Bottom value defined (i.e. the value of the parameter at the top of a soil layer and the bottom of a soil layer). The top value is pulled from the input text box for the parameter in the appropriate tab (ie. from the Immediate Settlement, Primary Consolidation, and Secondary Consolidation tabs). The bottom value is entered in the Value column. A linear variation is assumed between the top and bottom values.

Rate of Change

In this case, the rate of change is defined in the Value column. A positive or negative rate of change can be defined, and the value at a specific depth is calculated as:

Positive or negative rate of change equation

Rate of Change with Cutoff

The value with depth is calculated the same as in the above option. If the calculated value is outside of the cutoff value, the property value is set to the cutoff value.

Stage Factors

Any settlement parameter can be staged. The material properties are updated at the beginning of each stage.

Property Assist Dialogs

For most of the material input parameters in the Soil Properties dialog, you will notice a Pick icon beside the input edit box. If you select this button, you will see a dialog with published test results for a variety of soil types. This allows you to obtain reasonable estimates of parameter values, if you do not have your own analysis data.

Simply click on the most appropriate material listed in the dialog, and a corresponding value (or average value) will be loaded into the edit box of the dialog. Select OK and this value will be automatically entered in the Soil Properties dialog.

Liquefaction

The Liquefaction option allows you to define the Fines Content (%), and D50 (mm) value of the soil. There is also the Prone to Liquefaction checkbox, which is used to indicate whether a particular material should be included in the liquefaction analysis.

Undrained Shear Strength

The Undrained Shear Strength option allows you to define the parameters used to calculate undrained shear strength. This is a post-processing feature only. The settlement calculations are not affected by the undrained shear strength.

The equation for undrained shear strength is:

Undrained shear strength equation

In the Undrained Shear Strength dialog, you can specify the following parameters: A, S, m.

Layer Modulus

The Layer Modulus option allows you to define the elastic modulus of the soil, if you are using the Multiple Layer stress computation method. The Multiple Layer stress computation method requires a value of elastic modulus for each soil layer.

To define the Layer Modulus, select the Layer Modulus button. You will see another dialog which gives you three options for defining the layer modulus E for the soil type:

  • The first option allows you to enter a value of E directly.
  • The second option will set E equal to the value of Es which is entered for Immediate Settlement. This option is only enabled if the Immediate Settlement checkbox is selected in the Soil Properties dialog.
  • The third option will calculate E from the value of Cc entered for Primary Consolidation.

NOTE: the Layer Modulus option is only applicable if you are using the Multiple Layer stress computation method. It will NOT be available if you are using the Boussinesq or 2:1 stress computation methods.

Wick Drains

The Wick Drains option allows you to define the horizontal flow properties of each soil type, if you have defined a wick drain region. Horizontal flow is defined as a ratio, with respect to the vertical flow.

To define the horizontal flow, select the Wick Drains button. You will see another dialog which gives you two options for defining the horizontal flow for the soil type:

  • Ratio of horizontal to vertical coefficient of consolidation: Ch/Cv
  • Ratio of horizontal to vertical permeability: Kh/Kv

NOTE: the Wick Drains option is only applicable if you have defined a wick drain region.

Right Click Shortcut

In the 3D View, the Soil Properties and Soil Layers dialogs can be accessed with a right-click shortcut:

  1. Right-click on a soil layer in the 3D View representation of your soil column profile.
  2. Select Edit Soil Layer or Edit Soil Property to access the soil layer or soil property dialogs.
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