Transient Overview

To model time-dependent (transient) groundwater seepage analysis, the general procedure is the same as outlined for the Steady State groundwater seepage analysis, with the following additional steps.

Project Settings

On the Groundwater page of the Project Settings dialog:

• Set the Groundwater Method = Transient FEA
• Note that checking the box for "Define pwp method by stage" will allow you to select the groundwater method for each stage of the analysis under the "Stages" tab in Project Settings.

On the General page of the Project Settings dialog, you can choose:

• Solid-Fluid Interaction: None, Coupled (Biot), or Uncoupled
• Time Units and Permeability Units

On the Stages page of the Project Settings dialog:

• You must enter a time for each stage

Hydraulic Material Properties

In the Define Hydraulic Properties dialog you can define the permeability characteristics of your materials for groundwater seepage analysis, including additional parameters required for the transient analysis (e.g. water content curve).

In the Define Material Properties dialog, you can select the Initial Water Condition to be Dry, Pore Water Pressure, Ru, or Grid.

Groundwater Boundary Conditions

The hydraulic boundary conditions for seepage analysis are defined with the Set Boundary Conditions option in the Groundwater menu. For transient analysis you can define time-dependent boundary conditions (e.g. total head versus time, infiltration versus time, etc).

Discharge Sections

To compute the flow volume across a surface use the Add Discharge Section option in the Groundwater menu to define a discharge section.

Compute

The main Compute option will compute both seepage and stress analysis.

To compute the seepage analysis only (without computing the stress analysis), you can use the Compute Groundwater option. This allows you to view and verify the seepage analysis results, before proceeding to the stress analysis.

Groundwater Results

After computing a transient seepage analysis you can view contours of groundwater results at each stage (time) including pore pressure, total head, hydraulic gradient, velocity etc. If discharge sections were defined you can view the volumetric flow rates across any surface. Other results such as flow vectors can be displayed.