Defining an initial void ratio field

For Abaqus/Standard analyses you can specify the initial values of the void ratio, e, at the nodes of a porous medium (see Coupled pore fluid diffusion and stress analysis). The initial void ratio can be defined directly as an elevation-dependent function, by interpolation from the output database file of a previous Abaqus analysis, or by user subroutine VOIDRI. For more information, see Initial conditions in Abaqus/Standard and Abaqus/Explicit. You can create or modify an initial void ratio field only during the initial step.

Related Topics
Understanding symbols that represent prescribed conditions
Creating predefined fields
Using analytical expression fields
Creating expression fields
In Other Guides
Coupled pore fluid diffusion and stress analysis

  1. Display the initial void ratio field editor using one of the following methods:

  2. Click the arrow to the right of the Point 1 distribution field, and select the option of your choice from the list that appears:

    • Select Uniform to define a void ratio that is uniform for the selected region.

    • Select From output database file to read void ratio values from the output database file of a previous Abaqus analysis with void ratio components.

    • Select User-defined to specify void ratio using options in user subroutine VOIDRI. See the following sections for more information:

    • Select an analytical field to define a spatially varying initial void ratio. Alternatively, you can click to create a new analytical field. (See The Analytical Field toolset for more information.)

  3. For uniform distributions, do the following:

    1. From the Elevation distribution options, select either Linear or Constant.
    2. In the Void ratio 1 field, specify the initial void ratio in the first region in your model.
    3. If you selected an elevation distribution that varies linearly, specify the following options:

      • In the Vertical coordinate 1 field, specify the vertical position of the first location in your model for which you are specifying initial void ratio.

      • In the Point 2 distribution field, specify either a Uniform distribution for void ratio at the second elevation or select an analytical field to define a spatially varying initial void ratio at the second elevation. If you select Uniform, specify the void ratio and vertical position of the second location in your model.

  4. If you are specifying void ratio output from an output database file, do the following:

    1. Specify the file name from which you want to import void ratio values.
    2. From the Step options, either select Last to read void ratio output from the last step of the output database or select Specify and enter the number of the step from which you want to read void ratio data.
    3. From the Increment options, either select Last to read void ratio output from the last increment of the selected step or select Specify and enter the number of the increment from which you want to read void ratio data.
    4. Toggle on Interpolate midside nodes to interpolate void ratio values between dissimilar meshes.

  5. For user-defined void ratio distributions, do the following:

    1. Enter the Job module, and display the job editor for the analysis job of interest. (For more information, see Creating, editing, and manipulating jobs.)
    2. In the job editor, click the General tab, and specify the file containing the user subroutine that defines the predefined field. For more information, see Specifying general job settings.

      Note:

      You can specify only one user subroutine file in the job editor; if your analysis involves more than one user subroutine, you must combine the user subroutines into one file and then specify that file.

  6. Click OK to create the initial void ratio field and to close the dialog box.

    Sandy brown squares appear on the model representing the initial void ratio field that you just created.