Soil Layers

The Soil Layers option is used to define:

• the sequence of soil layers that make up your soil profile

• the thickness of each layer

• the drainage condition at the bottom of each layer

NOTE: it is assumed that all soil layers are horizontal and continuous

To define your soil layer profile:

1. Select Soil Layers from the toolbar or the Analysis menu.

2. In the Soil Layers dialog:

• click the Insert Layer Above or Insert Layer Below buttons to define the desired number and sequence of soil layers.

• for each layer, click on the Soil Name to select the soil type for each layer. The soil names correspond to the soil types defined in the Soil Properties dialog.

• enter the thickness of each layer

• as you enter the information in the dialog, an image of the soil profile will be displayed at the right of the dialog.

• if you need to delete a layer, click on the layer id number (at the left of the dialog) and select the Delete Layer button.

• If you are performing a time dependent consolidation analysis, you can define the drainage condition at the bottom of each layer, by selecting the Drained at Bottom checkbox for the desired layer(s). See below for more information about layer drainage.

3. When you are finished defining the soil profile, select OK, and the soil profile will be displayed in the 3D View and in the Sidebar.

NOTE:

• At least one load must be defined in order for the soil profile to be displayed in the 3D View.

• It is assumed that the entire soil layer profile rests on an impermeable layer of infinite stiffness (e.g. solid bedrock), so that the settlement at the bottom of the soil profile is always zero.

Layer Drainage

If the Time Dependent Consolidation Analysis option is selected in Project Settings, then you will be able to define the drainage condition at the bottom of each layer in the Soil Layers dialog. This allows you to define horizontal drainage at the interface between soil layers, as described below.

Drained at Bottom

For each soil layer, a Drained at Bottom checkbox can be selected in the Soil Layers dialog.

If this checkbox is selected, then the layer is assumed to be freely drained at the bottom (i.e. excess pore pressure will be automatically set to zero at the interface between layers).

If this checkbox is NOT selected, then the interface will NOT be a drainage path (i.e. excess pore pressure can exist at the interface).

Drained Ground Surface

By default, it is assumed that the ground surface is freely draining (i.e. excess pore pressure cannot exist at the ground surface). Consequently, the Drained Ground Surface checkbox (in the lower left corner of the Soil Layers dialog) is always turned on by default.

If for some reason you wish to define the ground surface as NOT freely drained, then you can turn OFF the Drained Ground Surface checkbox. If you do this, then excess pore pressure can exist at the ground surface (i.e. as if an impermeable membrane covered the ground surface).

NOTE: additional drainage conditions can be specified by defining wick drains, see the Add Wick Drain Region topic for details.

Right Click Shortcut

In the 3D View, the Soil Layers and Soil Properties 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.