Groundwater Analysis Overview

The groundwater options in RS2 allow you to determine pore pressure distributions which can be incorporated into the stress analysis to compute values of effective stress. Furthermore, if you choose the finite element seepage analysis options, a steady-state or transient seepage analysis can be carried out to compute pore pressures as well as flow rates and other hydraulic quantities. With transient seepage analysis consolidation problems can be analyzed.

To model groundwater in RS2:

1. First select the desired Groundwater Method in the Project Settings dialog. The following methods are available:
   • Static Water
   • Steady State Finite Element Seepage Analysis
   • Transient Finite Element Seepage Analysis
2. Use the applicable options (see below for details) to define the groundwater conditions for your model.

Static Water Mode

Piezometric Lines

1. Piezometric Lines are created with the Add Piezometric Line option in the Boundaries menu.
2. Piezometric Lines are then assigned to the desired materials and the staging sequence defined with the Define Hydraulic Properties option in the Properties menu.
3. If your piezo lines are staged, you can choose to view only the piezo line(s) applicable to the selected stage, with the View Piezos by Stage option in the Groundwater menu.

Water Pressure Grid

1. Water Pressure Grids are defined with the Water Pressure Grid option in the Groundwater menu.
2. Water Pressure grids can be assigned (or turned off) for each material with the Define Hydraulic Properties option.

Steady State Finite Element Seepage Analysis

If the Groundwater Method = Steady State FEA:

1. The hydraulic boundary conditions are defined with the Set Boundary Conditions option in the Groundwater menu.
2. The hydraulic material properties are defined with the Define Hydraulic Properties option in the Groundwater menu.
3. Optional - if you wish to compute the steady-state flow volume across a line segment, use the Add Discharge Section option in the Groundwater menu to define a discharge section.
4. Optional - if you wish to compute the seepage analysis only (without computing the stress analysis), then you can use the Compute (groundwater only) option. This allows you to view and verify the seepage analysis results, before proceeding to the effective stress analysis.

With finite element seepage analysis, the seepage analysis can be used to calculate pore pressures for an effective stress analysis, just as with the Piezometric Lines or Water Pressure Grid options. It can also be used as a standalone option, independently of the stress analysis in RS2 (i.e. you can run a seepage analysis without necessarily computing a stress analysis). Flow rates, hydraulic gradients and other quantities can be computed, in addition to pore pressure.

Transient Finite Element Seepage Analysis

If the Groundwater Method = Transient FEA:

• The input required for a Transient seepage analysis is the same as outlined above for a Steady State analysis, with some additional parameters required to define Transient time staging, boundary conditions and material parameters.

Discharge Sections

If the Groundwater Method = Steady State or Transient FEA, then you can define discharge sections to compute groundwater flow rate across user-defined sections. See the Discharge Section topic.